The proc filesystem is a pseudo-filesystem which provides an
interface to kernel data structures. It is commonly mounted at
/proc. Typically, it is mounted automatically by the system, but
it can also be mounted manually using a command such as:
mount -t proc proc /proc
Most of the files in the proc filesystem are read-only, but some
files are writable, allowing kernel variables to be changed.
Mount options
The proc filesystem supports the following mount options:
hidepid=n (since Linux 3.3)
This option controls who can access the information in
/proc/[pid] directories. The argument, n, is one of the
following values:
0 Everybody may access all /proc/[pid] directories.
This is the traditional behavior, and the default if
this mount option is not specified.
1 Users may not access files and subdirectories inside
any /proc/[pid] directories but their own (the
/proc/[pid] directories themselves remain visible).
Sensitive files such as /proc/[pid]/cmdline and
/proc/[pid]/status are now protected against other
users. This makes it impossible to learn whether any
user is running a specific program (so long as the
program doesn't otherwise reveal itself by its
behavior).
2 As for mode 1, but in addition the /proc/[pid]
directories belonging to other users become invisible.
This means that /proc/[pid] entries can no longer be
used to discover the PIDs on the system. This doesn't
hide the fact that a process with a specific PID value
exists (it can be learned by other means, for example,
by "kill -0 $PID"), but it hides a process's UID and
GID, which could otherwise be learned by employing
stat(2) on a /proc/[pid] directory. This greatly
complicates an attacker's task of gathering
information about running processes (e.g., discovering
whether some daemon is running with elevated
privileges, whether another user is running some
sensitive program, whether other users are running any
program at all, and so on).
gid=gid (since Linux 3.3)
Specifies the ID of a group whose members are authorized
to learn process information otherwise prohibited by
hidepid (i.e., users in this group behave as though /proc
was mounted with hidepid=0). This group should be used
instead of approaches such as putting nonroot users into
the sudoers(5) file.
Overview
Underneath /proc, there are the following general groups of files
and subdirectories:
/proc/[pid] subdirectories
Each one of these subdirectories contains files and
subdirectories exposing information about the process with
the corresponding process ID.
Underneath each of the /proc/[pid] directories, a task
subdirectory contains subdirectories of the form
task/[tid], which contain corresponding information about
each of the threads in the process, where tid is the
kernel thread ID of the thread.
The /proc/[pid] subdirectories are visible when iterating
through /proc with getdents(2) (and thus are visible when
one uses ls(1) to view the contents of /proc).
/proc/[tid] subdirectories
Each one of these subdirectories contains files and
subdirectories exposing information about the thread with
the corresponding thread ID. The contents of these
directories are the same as the corresponding
/proc/[pid]/task/[tid] directories.
The /proc/[tid] subdirectories are not visible when
iterating through /proc with getdents(2) (and thus are not
visible when one uses ls(1) to view the contents of
/proc).
/proc/self
When a process accesses this magic symbolic link, it
resolves to the process's own /proc/[pid] directory.
/proc/thread-self
When a thread accesses this magic symbolic link, it
resolves to the process's own /proc/self/task/[tid]
directory.
/proc/[a-z]*
Various other files and subdirectories under /proc expose
system-wide information.
All of the above are described in more detail below.
Files and directories
The following list provides details of many of the files and
directories under the /proc hierarchy.
/proc/[pid]
There is a numerical subdirectory for each running
process; the subdirectory is named by the process ID.
Each /proc/[pid] subdirectory contains the pseudo-files
and directories described below.
The files inside each /proc/[pid] directory are normally
owned by the effective user and effective group ID of the
process. However, as a security measure, the ownership is
made root:root if the process's "dumpable" attribute is
set to a value other than 1.
Before Linux 4.11, root:root meant the "global" root user
ID and group ID (i.e., UID 0 and GID 0 in the initial user
namespace). Since Linux 4.11, if the process is in a
noninitial user namespace that has a valid mapping for
user (group) ID 0 inside the namespace, then the user
(group) ownership of the files under /proc/[pid] is
instead made the same as the root user (group) ID of the
namespace. This means that inside a container, things
work as expected for the container "root" user.
The process's "dumpable" attribute may change for the
following reasons:
* The attribute was explicitly set via the prctl(2)
PR_SET_DUMPABLE operation.
* The attribute was reset to the value in the file
/proc/sys/fs/suid_dumpable (described below), for the
reasons described in prctl(2).
Resetting the "dumpable" attribute to 1 reverts the
ownership of the /proc/[pid]/* files to the process's
effective UID and GID. Note, however, that if the
effective UID or GID is subsequently modified, then the
"dumpable" attribute may be reset, as described in
prctl(2). Therefore, it may be desirable to reset the
"dumpable" attribute after making any desired changes to
the process's effective UID or GID.
/proc/[pid]/attr
The files in this directory provide an API for security
modules. The contents of this directory are files that
can be read and written in order to set security-related
attributes. This directory was added to support SELinux,
but the intention was that the API be general enough to
support other security modules. For the purpose of
explanation, examples of how SELinux uses these files are
provided below.
This directory is present only if the kernel was
configured with CONFIG_SECURITY.
/proc/[pid]/attr/current (since Linux 2.6.0)
The contents of this file represent the current security
attributes of the process.
In SELinux, this file is used to get the security context
of a process. Prior to Linux 2.6.11, this file could not
be used to set the security context (a write was always
denied), since SELinux limited process security
transitions to execve(2) (see the description of
/proc/[pid]/attr/exec, below). Since Linux 2.6.11,
SELinux lifted this restriction and began supporting "set"
operations via writes to this node if authorized by
policy, although use of this operation is only suitable
for applications that are trusted to maintain any desired
separation between the old and new security contexts.
Prior to Linux 2.6.28, SELinux did not allow threads
within a multithreaded process to set their security
context via this node as it would yield an inconsistency
among the security contexts of the threads sharing the
same memory space. Since Linux 2.6.28, SELinux lifted
this restriction and began supporting "set" operations for
threads within a multithreaded process if the new security
context is bounded by the old security context, where the
bounded relation is defined in policy and guarantees that
the new security context has a subset of the permissions
of the old security context.
Other security modules may choose to support "set"
operations via writes to this node.
/proc/[pid]/attr/exec (since Linux 2.6.0)
This file represents the attributes to assign to the
process upon a subsequent execve(2).
In SELinux, this is needed to support role/domain
transitions, and execve(2) is the preferred point to make
such transitions because it offers better control over the
initialization of the process in the new security label
and the inheritance of state. In SELinux, this attribute
is reset on execve(2) so that the new program reverts to
the default behavior for any execve(2) calls that it may
make. In SELinux, a process can set only its own
/proc/[pid]/attr/exec attribute.
/proc/[pid]/attr/fscreate (since Linux 2.6.0)
This file represents the attributes to assign to files
created by subsequent calls to open(2), mkdir(2),
symlink(2), and mknod(2)
SELinux employs this file to support creation of a file
(using the aforementioned system calls) in a secure state,
so that there is no risk of inappropriate access being
obtained between the time of creation and the time that
attributes are set. In SELinux, this attribute is reset
on execve(2), so that the new program reverts to the
default behavior for any file creation calls it may make,
but the attribute will persist across multiple file
creation calls within a program unless it is explicitly
reset. In SELinux, a process can set only its own
/proc/[pid]/attr/fscreate attribute.
/proc/[pid]/attr/keycreate (since Linux 2.6.18)
If a process writes a security context into this file, all
subsequently created keys (add_key(2)) will be labeled
with this context. For further information, see the
kernel source file Documentation/security/keys/core.rst
(or file Documentation/security/keys.txt on Linux between
3.0 and 4.13, or Documentation/keys.txt before Linux 3.0).
/proc/[pid]/attr/prev (since Linux 2.6.0)
This file contains the security context of the process
before the last execve(2); that is, the previous value of
/proc/[pid]/attr/current.
/proc/[pid]/attr/socketcreate (since Linux 2.6.18)
If a process writes a security context into this file, all
subsequently created sockets will be labeled with this
context.
/proc/[pid]/autogroup (since Linux 2.6.38)
See sched(7).
/proc/[pid]/auxv (since 2.6.0)
This contains the contents of the ELF interpreter
information passed to the process at exec time. The
format is one unsigned long ID plus one unsigned long
value for each entry. The last entry contains two zeros.
See also getauxval(3).
Permission to access this file is governed by a ptrace
access mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
/proc/[pid]/cgroup (since Linux 2.6.24)
See cgroups(7).
/proc/[pid]/clear_refs (since Linux 2.6.22)
This is a write-only file, writable only by owner of the
process.
The following values may be written to the file:
1 (since Linux 2.6.22)
Reset the PG_Referenced and ACCESSED/YOUNG bits for
all the pages associated with the process. (Before
kernel 2.6.32, writing any nonzero value to this
file had this effect.)
2 (since Linux 2.6.32)
Reset the PG_Referenced and ACCESSED/YOUNG bits for
all anonymous pages associated with the process.
3 (since Linux 2.6.32)
Reset the PG_Referenced and ACCESSED/YOUNG bits for
all file-mapped pages associated with the process.
Clearing the PG_Referenced and ACCESSED/YOUNG bits
provides a method to measure approximately how much memory
a process is using. One first inspects the values in the
"Referenced" fields for the VMAs shown in
/proc/[pid]/smaps to get an idea of the memory footprint
of the process. One then clears the PG_Referenced and
ACCESSED/YOUNG bits and, after some measured time
interval, once again inspects the values in the
"Referenced" fields to get an idea of the change in memory
footprint of the process during the measured interval. If
one is interested only in inspecting the selected mapping
types, then the value 2 or 3 can be used instead of 1.
Further values can be written to affect different
properties:
4 (since Linux 3.11)
Clear the soft-dirty bit for all the pages
associated with the process. This is used (in
conjunction with /proc/[pid]/pagemap) by the check-
point restore system to discover which pages of a
process have been dirtied since the file
/proc/[pid]/clear_refs was written to.
5 (since Linux 4.0)
Reset the peak resident set size ("high water
mark") to the process's current resident set size
value.
Writing any value to /proc/[pid]/clear_refs other than
those listed above has no effect.
The /proc/[pid]/clear_refs file is present only if the
CONFIG_PROC_PAGE_MONITOR kernel configuration option is
enabled.
/proc/[pid]/cmdline
This read-only file holds the complete command line for
the process, unless the process is a zombie. In the
latter case, there is nothing in this file: that is, a
read on this file will return 0 characters. The command-
line arguments appear in this file as a set of strings
separated by null bytes ('\0'), with a further null byte
after the last string.
If, after an execve(2), the process modifies its argv
strings, those changes will show up here. This is not the
same thing as modifying the argv array.
Furthermore, a process may change the memory location that
this file refers via prctl(2) operations such as
PR_SET_MM_ARG_START.
Think of this file as the command line that the process
wants you to see.
/proc/[pid]/comm (since Linux 2.6.33)
This file exposes the process's comm value—that is, the
command name associated with the process. Different
threads in the same process may have different comm
values, accessible via /proc/[pid]/task/[tid]/comm. A
thread may modify its comm value, or that of any of other
thread in the same thread group (see the discussion of
CLONE_THREAD in clone(2)), by writing to the file
/proc/self/task/[tid]/comm. Strings longer than
TASK_COMM_LEN (16) characters (including the terminating
null byte) are silently truncated.
This file provides a superset of the prctl(2) PR_SET_NAME
and PR_GET_NAME operations, and is employed by
pthread_setname_np(3) when used to rename threads other
than the caller. The value in this file is used for the
%e specifier in /proc/sys/kernel/core_pattern; see
core(5).
/proc/[pid]/coredump_filter (since Linux 2.6.23)
See core(5).
/proc/[pid]/cpuset (since Linux 2.6.12)
See cpuset(7).
/proc/[pid]/cwd
This is a symbolic link to the current working directory
of the process. To find out the current working directory
of process 20, for instance, you can do this:
$ cd /proc/20/cwd; pwd -P
In a multithreaded process, the contents of this symbolic
link are not available if the main thread has already
terminated (typically by calling pthread_exit(3)).
Permission to dereference or read (readlink(2)) this
symbolic link is governed by a ptrace access mode
PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
/proc/[pid]/environ
This file contains the initial environment that was set
when the currently executing program was started via
execve(2). The entries are separated by null bytes
('\0'), and there may be a null byte at the end. Thus, to
print out the environment of process 1, you would do:
$ cat /proc/1/environ | tr '\000' '\n'
If, after an execve(2), the process modifies its
environment (e.g., by calling functions such as putenv(3)
or modifying the environ(7) variable directly), this file
will not reflect those changes.
Furthermore, a process may change the memory location that
this file refers via prctl(2) operations such as
PR_SET_MM_ENV_START.
Permission to access this file is governed by a ptrace
access mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
/proc/[pid]/exe
Under Linux 2.2 and later, this file is a symbolic link
containing the actual pathname of the executed command.
This symbolic link can be dereferenced normally;
attempting to open it will open the executable. You can
even type /proc/[pid]/exe to run another copy of the same
executable that is being run by process [pid]. If the
pathname has been unlinked, the symbolic link will contain
the string '(deleted)' appended to the original pathname.
In a multithreaded process, the contents of this symbolic
link are not available if the main thread has already
terminated (typically by calling pthread_exit(3)).
Permission to dereference or read (readlink(2)) this
symbolic link is governed by a ptrace access mode
PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
Under Linux 2.0 and earlier, /proc/[pid]/exe is a pointer
to the binary which was executed, and appears as a
symbolic link. A readlink(2) call on this file under
Linux 2.0 returns a string in the format:
[device]:inode
For example, [0301]:1502 would be inode 1502 on device
major 03 (IDE, MFM, etc. drives) minor 01 (first partition
on the first drive).
find(1) with the -inum option can be used to locate the
file.
/proc/[pid]/fd/
This is a subdirectory containing one entry for each file
which the process has open, named by its file descriptor,
and which is a symbolic link to the actual file. Thus, 0
is standard input, 1 standard output, 2 standard error,
and so on.
For file descriptors for pipes and sockets, the entries
will be symbolic links whose content is the file type with
the inode. A readlink(2) call on this file returns a
string in the format:
type:[inode]
For example, socket:[2248868] will be a socket and its
inode is 2248868. For sockets, that inode can be used to
find more information in one of the files under
/proc/net/.
For file descriptors that have no corresponding inode
(e.g., file descriptors produced by bpf(2),
epoll_create(2), eventfd(2), inotify_init(2),
perf_event_open(2), signalfd(2), timerfd_create(2), and
userfaultfd(2)), the entry will be a symbolic link with
contents of the form
anon_inode:<file-type>
In many cases (but not all), the file-type is surrounded
by square brackets.
For example, an epoll file descriptor will have a symbolic
link whose content is the string anon_inode:[eventpoll].
In a multithreaded process, the contents of this directory
are not available if the main thread has already
terminated (typically by calling pthread_exit(3)).
Programs that take a filename as a command-line argument,
but don't take input from standard input if no argument is
supplied, and programs that write to a file named as a
command-line argument, but don't send their output to
standard output if no argument is supplied, can
nevertheless be made to use standard input or standard
output by using /proc/[pid]/fd files as command-line
arguments. For example, assuming that -i is the flag
designating an input file and -o is the flag designating
an output file:
$ foobar -i /proc/self/fd/0 -o /proc/self/fd/1 ...
and you have a working filter.
/proc/self/fd/N is approximately the same as /dev/fd/N in
some UNIX and UNIX-like systems. Most Linux MAKEDEV
scripts symbolically link /dev/fd to /proc/self/fd, in
fact.
Most systems provide symbolic links /dev/stdin,
/dev/stdout, and /dev/stderr, which respectively link to
the files 0, 1, and 2 in /proc/self/fd. Thus the example
command above could be written as:
$ foobar -i /dev/stdin -o /dev/stdout ...
Permission to dereference or read (readlink(2)) the
symbolic links in this directory is governed by a ptrace
access mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
Note that for file descriptors referring to inodes (pipes
and sockets, see above), those inodes still have
permission bits and ownership information distinct from
those of the /proc/[pid]/fd entry, and that the owner may
differ from the user and group IDs of the process. An
unprivileged process may lack permissions to open them, as
in this example:
$ echo test | sudo -u nobody cat
test
$ echo test | sudo -u nobody cat /proc/self/fd/0
cat: /proc/self/fd/0: Permission denied
File descriptor 0 refers to the pipe created by the shell
and owned by that shell's user, which is not nobody, so
cat does not have permission to create a new file
descriptor to read from that inode, even though it can
still read from its existing file descriptor 0.
/proc/[pid]/fdinfo/ (since Linux 2.6.22)
This is a subdirectory containing one entry for each file
which the process has open, named by its file descriptor.
The files in this directory are readable only by the owner
of the process. The contents of each file can be read to
obtain information about the corresponding file
descriptor. The content depends on the type of file
referred to by the corresponding file descriptor.
For regular files and directories, we see something like:
$ cat /proc/12015/fdinfo/4
pos: 1000
flags: 01002002
mnt_id: 21
The fields are as follows:
pos This is a decimal number showing the file offset.
flags This is an octal number that displays the file
access mode and file status flags (see open(2)).
If the close-on-exec file descriptor flag is set,
then flags will also include the value O_CLOEXEC.
Before Linux 3.1, this field incorrectly displayed
the setting of O_CLOEXEC at the time the file was
opened, rather than the current setting of the
close-on-exec flag.
mnt_id This field, present since Linux 3.15, is the ID of
the mount containing this file. See the
description of /proc/[pid]/mountinfo.
For eventfd file descriptors (see eventfd(2)), we see
(since Linux 3.8) the following fields:
pos: 0
flags: 02
mnt_id: 10
eventfd-count: 40
eventfd-count is the current value of the eventfd counter,
in hexadecimal.
For epoll file descriptors (see epoll(7)), we see (since
Linux 3.8) the following fields:
pos: 0
flags: 02
mnt_id: 10
tfd: 9 events: 19 data: 74253d2500000009
tfd: 7 events: 19 data: 74253d2500000007
Each of the lines beginning tfd describes one of the file
descriptors being monitored via the epoll file descriptor
(see epoll_ctl(2) for some details). The tfd field is the
number of the file descriptor. The events field is a
hexadecimal mask of the events being monitored for this
file descriptor. The data field is the data value
associated with this file descriptor.
For signalfd file descriptors (see signalfd(2)), we see
(since Linux 3.8) the following fields:
pos: 0
flags: 02
mnt_id: 10
sigmask: 0000000000000006
sigmask is the hexadecimal mask of signals that are
accepted via this signalfd file descriptor. (In this
example, bits 2 and 3 are set, corresponding to the
signals SIGINT and SIGQUIT; see signal(7).)
For inotify file descriptors (see inotify(7)), we see
(since Linux 3.8) the following fields:
pos: 0
flags: 00
mnt_id: 11
inotify wd:2 ino:7ef82a sdev:800001 mask:800afff ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:2af87e00220ffd73
inotify wd:1 ino:192627 sdev:800001 mask:800afff ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:27261900802dfd73
Each of the lines beginning with "inotify" displays
information about one file or directory that is being
monitored. The fields in this line are as follows:
wd A watch descriptor number (in decimal).
ino The inode number of the target file (in
hexadecimal).
sdev The ID of the device where the target file resides
(in hexadecimal).
mask The mask of events being monitored for the target
file (in hexadecimal).
If the kernel was built with exportfs support, the path to
the target file is exposed as a file handle, via three
hexadecimal fields: fhandle-bytes, fhandle-type, and
f_handle.
For fanotify file descriptors (see fanotify(7)), we see
(since Linux 3.8) the following fields:
pos: 0
flags: 02
mnt_id: 11
fanotify flags:0 event-flags:88002
fanotify ino:19264f sdev:800001 mflags:0 mask:1 ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:4f261900a82dfd73
The fourth line displays information defined when the
fanotify group was created via fanotify_init(2):
flags The flags argument given to fanotify_init(2)
(expressed in hexadecimal).
event-flags
The event_f_flags argument given to
fanotify_init(2) (expressed in hexadecimal).
Each additional line shown in the file contains
information about one of the marks in the fanotify group.
Most of these fields are as for inotify, except:
mflags The flags associated with the mark (expressed in
hexadecimal).
mask The events mask for this mark (expressed in
hexadecimal).
ignored_mask
The mask of events that are ignored for this mark
(expressed in hexadecimal).
For details on these fields, see fanotify_mark(2).
For timerfd file descriptors (see timerfd(2)), we see
(since Linux 3.17) the following fields:
pos: 0
flags: 02004002
mnt_id: 13
clockid: 0
ticks: 0
settime flags: 03
it_value: (7695568592, 640020877)
it_interval: (0, 0)
clockid
This is the numeric value of the clock ID
(corresponding to one of the CLOCK_* constants
defined via <time.h>) that is used to mark the
progress of the timer (in this example, 0 is
CLOCK_REALTIME).
ticks This is the number of timer expirations that have
occurred, (i.e., the value that read(2) on it would
return).
settime flags
This field lists the flags with which the timerfd
was last armed (see timerfd_settime(2)), in octal
(in this example, both TFD_TIMER_ABSTIME and
TFD_TIMER_CANCEL_ON_SET are set).
it_value
This field contains the amount of time until the
timer will next expire, expressed in seconds and
nanoseconds. This is always expressed as a
relative value, regardless of whether the timer was
created using the TFD_TIMER_ABSTIME flag.
it_interval
This field contains the interval of the timer, in
seconds and nanoseconds. (The it_value and
it_interval fields contain the values that
timerfd_gettime(2) on this file descriptor would
return.)
/proc/[pid]/gid_map (since Linux 3.5)
See user_namespaces(7).
/proc/[pid]/io (since kernel 2.6.20)
This file contains I/O statistics for the process, for
example:
# cat /proc/3828/io
rchar: 323934931
wchar: 323929600
syscr: 632687
syscw: 632675
read_bytes: 0
write_bytes: 323932160
cancelled_write_bytes: 0
The fields are as follows:
rchar: characters read
The number of bytes which this task has caused to
be read from storage. This is simply the sum of
bytes which this process passed to read(2) and
similar system calls. It includes things such as
terminal I/O and is unaffected by whether or not
actual physical disk I/O was required (the read
might have been satisfied from pagecache).
wchar: characters written
The number of bytes which this task has caused, or
shall cause to be written to disk. Similar caveats
apply here as with rchar.
syscr: read syscalls
Attempt to count the number of read I/O operations—
that is, system calls such as read(2) and pread(2).
syscw: write syscalls
Attempt to count the number of write I/O
operations—that is, system calls such as write(2)
and pwrite(2).
read_bytes: bytes read
Attempt to count the number of bytes which this
process really did cause to be fetched from the
storage layer. This is accurate for block-backed
filesystems.
write_bytes: bytes written
Attempt to count the number of bytes which this
process caused to be sent to the storage layer.
cancelled_write_bytes:
The big inaccuracy here is truncate. If a process
writes 1 MB to a file and then deletes the file, it
will in fact perform no writeout. But it will have
been accounted as having caused 1 MB of write. In
other words: this field represents the number of
bytes which this process caused to not happen, by
truncating pagecache. A task can cause "negative"
I/O too. If this task truncates some dirty
pagecache, some I/O which another task has been
accounted for (in its write_bytes) will not be
happening.
Note: In the current implementation, things are a bit racy
on 32-bit systems: if process A reads process B's
/proc/[pid]/io while process B is updating one of these
64-bit counters, process A could see an intermediate
result.
Permission to access this file is governed by a ptrace
access mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
/proc/[pid]/limits (since Linux 2.6.24)
This file displays the soft limit, hard limit, and units
of measurement for each of the process's resource limits
(see getrlimit(2)). Up to and including Linux 2.6.35,
this file is protected to allow reading only by the real
UID of the process. Since Linux 2.6.36, this file is
readable by all users on the system.
/proc/[pid]/map_files/ (since kernel 3.3)
This subdirectory contains entries corresponding to
memory-mapped files (see mmap(2)). Entries are named by
memory region start and end address pair (expressed as
hexadecimal numbers), and are symbolic links to the mapped
files themselves. Here is an example, with the output
wrapped and reformatted to fit on an 80-column display:
# ls -l /proc/self/map_files/
lr--------. 1 root root 64 Apr 16 21:31
3252e00000-3252e20000 -> /usr/lib64/ld-2.15.so
...
Although these entries are present for memory regions that
were mapped with the MAP_FILE flag, the way anonymous
shared memory (regions created with the MAP_ANON |
MAP_SHARED flags) is implemented in Linux means that such
regions also appear on this directory. Here is an example
where the target file is the deleted /dev/zero one:
lrw-------. 1 root root 64 Apr 16 21:33
7fc075d2f000-7fc075e6f000 -> /dev/zero (deleted)
Permission to access this file is governed by a ptrace
access mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
Until kernel version 4.3, this directory appeared only if
the CONFIG_CHECKPOINT_RESTORE kernel configuration option
was enabled.
Capabilities are required to read the contents of the
symbolic links in this directory: before Linux 5.9, the
reading process requires CAP_SYS_ADMIN in the initial user
namespace; since Linux 5.9, the reading process must have
either CAP_SYS_ADMIN or CAP_CHECKPOINT_RESTORE in the user
namespace where it resides.
/proc/[pid]/maps
A file containing the currently mapped memory regions and
their access permissions. See mmap(2) for some further
information about memory mappings.
Permission to access this file is governed by a ptrace
access mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
The format of the file is:
address perms offset dev inode pathname
00400000-00452000 r-xp 00000000 08:02 173521 /usr/bin/dbus-daemon
00651000-00652000 r--p 00051000 08:02 173521 /usr/bin/dbus-daemon
00652000-00655000 rw-p 00052000 08:02 173521 /usr/bin/dbus-daemon
00e03000-00e24000 rw-p 00000000 00:00 0 [heap]
00e24000-011f7000 rw-p 00000000 00:00 0 [heap]
...
35b1800000-35b1820000 r-xp 00000000 08:02 135522 /usr/lib64/ld-2.15.so
35b1a1f000-35b1a20000 r--p 0001f000 08:02 135522 /usr/lib64/ld-2.15.so
35b1a20000-35b1a21000 rw-p 00020000 08:02 135522 /usr/lib64/ld-2.15.so
35b1a21000-35b1a22000 rw-p 00000000 00:00 0
35b1c00000-35b1dac000 r-xp 00000000 08:02 135870 /usr/lib64/libc-2.15.so
35b1dac000-35b1fac000 ---p 001ac000 08:02 135870 /usr/lib64/libc-2.15.so
35b1fac000-35b1fb0000 r--p 001ac000 08:02 135870 /usr/lib64/libc-2.15.so
35b1fb0000-35b1fb2000 rw-p 001b0000 08:02 135870 /usr/lib64/libc-2.15.so
...
f2c6ff8c000-7f2c7078c000 rw-p 00000000 00:00 0 [stack:986]
...
7fffb2c0d000-7fffb2c2e000 rw-p 00000000 00:00 0 [stack]
7fffb2d48000-7fffb2d49000 r-xp 00000000 00:00 0 [vdso]
The address field is the address space in the process that
the mapping occupies. The perms field is a set of
permissions:
r = read
w = write
x = execute
s = shared
p = private (copy on write)
The offset field is the offset into the file/whatever; dev
is the device (major:minor); inode is the inode on that
device. 0 indicates that no inode is associated with the
memory region, as would be the case with BSS
(uninitialized data).
The pathname field will usually be the file that is
backing the mapping. For ELF files, you can easily
coordinate with the offset field by looking at the Offset
field in the ELF program headers (readelf -l).
There are additional helpful pseudo-paths:
[stack]
The initial process's (also known as the main
thread's) stack.
[stack:<tid>] (from Linux 3.4 to 4.4)
A thread's stack (where the <tid> is a thread ID).
It corresponds to the /proc/[pid]/task/[tid]/ path.
This field was removed in Linux 4.5, since
providing this information for a process with large
numbers of threads is expensive.
[vdso] The virtual dynamically linked shared object. See
vdso(7).
[heap] The process's heap.
If the pathname field is blank, this is an anonymous
mapping as obtained via mmap(2). There is no easy way to
coordinate this back to a process's source, short of
running it through gdb(1), strace(1), or similar.
pathname is shown unescaped except for newline characters,
which are replaced with an octal escape sequence. As a
result, it is not possible to determine whether the
original pathname contained a newline character or the
literal \012 character sequence.
If the mapping is file-backed and the file has been
deleted, the string " (deleted)" is appended to the
pathname. Note that this is ambiguous too.
Under Linux 2.0, there is no field giving pathname.
/proc/[pid]/mem
This file can be used to access the pages of a process's
memory through open(2), read(2), and lseek(2).
Permission to access this file is governed by a ptrace
access mode PTRACE_MODE_ATTACH_FSCREDS check; see
ptrace(2).
/proc/[pid]/mountinfo (since Linux 2.6.26)
This file contains information about mounts in the
process's mount namespace (see mount_namespaces(7)). It
supplies various information (e.g., propagation state,
root of mount for bind mounts, identifier for each mount
and its parent) that is missing from the (older)
/proc/[pid]/mounts file, and fixes various other problems
with that file (e.g., nonextensibility, failure to
distinguish per-mount versus per-superblock options).
The file contains lines of the form:
36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
(1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
The numbers in parentheses are labels for the descriptions
below:
(1) mount ID: a unique ID for the mount (may be reused
after umount(2)).
(2) parent ID: the ID of the parent mount (or of self for
the root of this mount namespace's mount tree).
If a new mount is stacked on top of a previous
existing mount (so that it hides the existing mount)
at pathname P, then the parent of the new mount is
the previous mount at that location. Thus, when
looking at all the mounts stacked at a particular
location, the top-most mount is the one that is not
the parent of any other mount at the same location.
(Note, however, that this top-most mount will be
accessible only if the longest path subprefix of P
that is a mount point is not itself hidden by a
stacked mount.)
If the parent mount lies outside the process's root
directory (see chroot(2)), the ID shown here won't
have a corresponding record in mountinfo whose mount
ID (field 1) matches this parent mount ID (because
mounts that lie outside the process's root directory
are not shown in mountinfo). As a special case of
this point, the process's root mount may have a
parent mount (for the initramfs filesystem) that lies
outside the process's root directory, and an entry
for that mount will not appear in mountinfo.
(3) major:minor: the value of st_dev for files on this
filesystem (see stat(2)).
(4) root: the pathname of the directory in the filesystem
which forms the root of this mount.
(5) mount point: the pathname of the mount point relative
to the process's root directory.
(6) mount options: per-mount options (see mount(2)).
(7) optional fields: zero or more fields of the form
"tag[:value]"; see below.
(8) separator: the end of the optional fields is marked
by a single hyphen.
(9) filesystem type: the filesystem type in the form
"type[.subtype]".
(10) mount source: filesystem-specific information or
"none".
(11) super options: per-superblock options (see mount(2)).
Currently, the possible optional fields are shared,
master, propagate_from, and unbindable. See
mount_namespaces(7) for a description of these fields.
Parsers should ignore all unrecognized optional fields.
For more information on mount propagation see:
Documentation/filesystems/sharedsubtree.txt in the Linux
kernel source tree.
/proc/[pid]/mounts (since Linux 2.4.19)
This file lists all the filesystems currently mounted in
the process's mount namespace (see mount_namespaces(7)).
The format of this file is documented in fstab(5).
Since kernel version 2.6.15, this file is pollable: after
opening the file for reading, a change in this file (i.e.,
a filesystem mount or unmount) causes select(2) to mark
the file descriptor as having an exceptional condition,
and poll(2) and epoll_wait(2) mark the file as having a
priority event (POLLPRI). (Before Linux 2.6.30, a change
in this file was indicated by the file descriptor being
marked as readable for select(2), and being marked as
having an error condition for poll(2) and epoll_wait(2).)
/proc/[pid]/mountstats (since Linux 2.6.17)
This file exports information (statistics, configuration
information) about the mounts in the process's mount
namespace (see mount_namespaces(7)). Lines in this file
have the form:
device /dev/sda7 mounted on /home with fstype ext3 [stats]
( 1 ) ( 2 ) (3 ) ( 4 )
The fields in each line are:
(1) The name of the mounted device (or "nodevice" if
there is no corresponding device).
(2) The mount point within the filesystem tree.
(3) The filesystem type.
(4) Optional statistics and configuration information.
Currently (as at Linux 2.6.26), only NFS filesystems
export information via this field.
This file is readable only by the owner of the process.
/proc/[pid]/net (since Linux 2.6.25)
See the description of /proc/net.
/proc/[pid]/ns/ (since Linux 3.0)
This is a subdirectory containing one entry for each
namespace that supports being manipulated by setns(2).
For more information, see namespaces(7).
/proc/[pid]/numa_maps (since Linux 2.6.14)
See numa(7).
/proc/[pid]/oom_adj (since Linux 2.6.11)
This file can be used to adjust the score used to select
which process should be killed in an out-of-memory (OOM)
situation. The kernel uses this value for a bit-shift
operation of the process's oom_score value: valid values
are in the range -16 to +15, plus the special value -17,
which disables OOM-killing altogether for this process. A
positive score increases the likelihood of this process
being killed by the OOM-killer; a negative score decreases
the likelihood.
The default value for this file is 0; a new process
inherits its parent's oom_adj setting. A process must be
privileged (CAP_SYS_RESOURCE) to update this file.
Since Linux 2.6.36, use of this file is deprecated in
favor of /proc/[pid]/oom_score_adj.
/proc/[pid]/oom_score (since Linux 2.6.11)
This file displays the current score that the kernel gives
to this process for the purpose of selecting a process for
the OOM-killer. A higher score means that the process is
more likely to be selected by the OOM-killer. The basis
for this score is the amount of memory used by the
process, with increases (+) or decreases (-) for factors
including:
* whether the process is privileged (-).
Before kernel 2.6.36 the following factors were also used
in the calculation of oom_score:
* whether the process creates a lot of children using
fork(2) (+);
* whether the process has been running a long time, or has
used a lot of CPU time (-);
* whether the process has a low nice value (i.e., > 0)
(+); and
* whether the process is making direct hardware access
(-).
The oom_score also reflects the adjustment specified by
the oom_score_adj or oom_adj setting for the process.
/proc/[pid]/oom_score_adj (since Linux 2.6.36)
This file can be used to adjust the badness heuristic used
to select which process gets killed in out-of-memory
conditions.
The badness heuristic assigns a value to each candidate
task ranging from 0 (never kill) to 1000 (always kill) to
determine which process is targeted. The units are
roughly a proportion along that range of allowed memory
the process may allocate from, based on an estimation of
its current memory and swap use. For example, if a task
is using all allowed memory, its badness score will be
1000. If it is using half of its allowed memory, its
score will be 500.
There is an additional factor included in the badness
score: root processes are given 3% extra memory over other
tasks.
The amount of "allowed" memory depends on the context in
which the OOM-killer was called. If it is due to the
memory assigned to the allocating task's cpuset being
exhausted, the allowed memory represents the set of mems
assigned to that cpuset (see cpuset(7)). If it is due to
a mempolicy's node(s) being exhausted, the allowed memory
represents the set of mempolicy nodes. If it is due to a
memory limit (or swap limit) being reached, the allowed
memory is that configured limit. Finally, if it is due to
the entire system being out of memory, the allowed memory
represents all allocatable resources.
The value of oom_score_adj is added to the badness score
before it is used to determine which task to kill.
Acceptable values range from -1000 (OOM_SCORE_ADJ_MIN) to
+1000 (OOM_SCORE_ADJ_MAX). This allows user space to
control the preference for OOM-killing, ranging from
always preferring a certain task or completely disabling
it from OOM-killing. The lowest possible value, -1000, is
equivalent to disabling OOM-killing entirely for that
task, since it will always report a badness score of 0.
Consequently, it is very simple for user space to define
the amount of memory to consider for each task. Setting
an oom_score_adj value of +500, for example, is roughly
equivalent to allowing the remainder of tasks sharing the
same system, cpuset, mempolicy, or memory controller
resources to use at least 50% more memory. A value of
-500, on the other hand, would be roughly equivalent to
discounting 50% of the task's allowed memory from being
considered as scoring against the task.
For backward compatibility with previous kernels,
/proc/[pid]/oom_adj can still be used to tune the badness
score. Its value is scaled linearly with oom_score_adj.
Writing to /proc/[pid]/oom_score_adj or
/proc/[pid]/oom_adj will change the other with its scaled
value.
The choom(1) program provides a command-line interface for
adjusting the oom_score_adj value of a running process or
a newly executed command.
/proc/[pid]/pagemap (since Linux 2.6.25)
This file shows the mapping of each of the process's
virtual pages into physical page frames or swap area. It
contains one 64-bit value for each virtual page, with the
bits set as follows:
63 If set, the page is present in RAM.
62 If set, the page is in swap space
61 (since Linux 3.5)
The page is a file-mapped page or a shared
anonymous page.
60–57 (since Linux 3.11)
Zero
56 (since Linux 4.2)
The page is exclusively mapped.
55 (since Linux 3.11)
PTE is soft-dirty (see the kernel source file
Documentation/admin-guide/mm/soft-dirty.rst).
54–0 If the page is present in RAM (bit 63), then these
bits provide the page frame number, which can be
used to index /proc/kpageflags and
/proc/kpagecount. If the page is present in swap
(bit 62), then bits 4–0 give the swap type, and
bits 54–5 encode the swap offset.
Before Linux 3.11, bits 60–55 were used to encode the
base-2 log of the page size.
To employ /proc/[pid]/pagemap efficiently, use
/proc/[pid]/maps to determine which areas of memory are
actually mapped and seek to skip over unmapped regions.
The /proc/[pid]/pagemap file is present only if the
CONFIG_PROC_PAGE_MONITOR kernel configuration option is
enabled.
Permission to access this file is governed by a ptrace
access mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
/proc/[pid]/personality (since Linux 2.6.28)
This read-only file exposes the process's execution
domain, as set by personality(2). The value is displayed
in hexadecimal notation.
Permission to access this file is governed by a ptrace
access mode PTRACE_MODE_ATTACH_FSCREDS check; see
ptrace(2).
/proc/[pid]/root
UNIX and Linux support the idea of a per-process root of
the filesystem, set by the chroot(2) system call. This
file is a symbolic link that points to the process's root
directory, and behaves in the same way as exe, and fd/*.
Note however that this file is not merely a symbolic link.
It provides the same view of the filesystem (including
namespaces and the set of per-process mounts) as the
process itself. An example illustrates this point. In
one terminal, we start a shell in new user and mount
namespaces, and in that shell we create some new mounts:
$ PS1='sh1# ' unshare -Urnm
sh1# mount -t tmpfs tmpfs /etc # Mount empty tmpfs at /etc
sh1# mount --bind /usr /dev # Mount /usr at /dev
sh1# echo $$
27123
In a second terminal window, in the initial mount
namespace, we look at the contents of the corresponding
mounts in the initial and new namespaces:
$ PS1='sh2# ' sudo sh
sh2# ls /etc | wc -l # In initial NS
309
sh2# ls /proc/27123/root/etc | wc -l # /etc in other NS
0 # The empty tmpfs dir
sh2# ls /dev | wc -l # In initial NS
205
sh2# ls /proc/27123/root/dev | wc -l # /dev in other NS
11 # Actually bind
# mounted to /usr
sh2# ls /usr | wc -l # /usr in initial NS
11
In a multithreaded process, the contents of the
/proc/[pid]/root symbolic link are not available if the
main thread has already terminated (typically by calling
pthread_exit(3)).
Permission to dereference or read (readlink(2)) this
symbolic link is governed by a ptrace access mode
PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
/proc/[pid]/projid_map (since Linux 3.7)
See user_namespaces(7).
/proc/[pid]/seccomp (Linux 2.6.12 to 2.6.22)
This file can be used to read and change the process's
secure computing (seccomp) mode setting. It contains the
value 0 if the process is not in seccomp mode, and 1 if
the process is in strict seccomp mode (see seccomp(2)).
Writing 1 to this file places the process irreversibly in
strict seccomp mode. (Further attempts to write to the
file fail with the EPERM error.)
In Linux 2.6.23, this file went away, to be replaced by
the prctl(2) PR_GET_SECCOMP and PR_SET_SECCOMP operations
(and later by seccomp(2) and the Seccomp field in
/proc/[pid]/status).
/proc/[pid]/setgroups (since Linux 3.19)
See user_namespaces(7).
/proc/[pid]/smaps (since Linux 2.6.14)
This file shows memory consumption for each of the
process's mappings. (The pmap(1) command displays similar
information, in a form that may be easier for parsing.)
For each mapping there is a series of lines such as the
following:
00400000-0048a000 r-xp 00000000 fd:03 960637 /bin/bash
Size: 552 kB
Rss: 460 kB
Pss: 100 kB
Shared_Clean: 452 kB
Shared_Dirty: 0 kB
Private_Clean: 8 kB
Private_Dirty: 0 kB
Referenced: 460 kB
Anonymous: 0 kB
AnonHugePages: 0 kB
ShmemHugePages: 0 kB
ShmemPmdMapped: 0 kB
Swap: 0 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
KernelPageSize: 4 kB
MMUPageSize: 4 kB
Locked: 0 kB
ProtectionKey: 0
VmFlags: rd ex mr mw me dw
The first of these lines shows the same information as is
displayed for the mapping in /proc/[pid]/maps. The
following lines show the size of the mapping, the amount
of the mapping that is currently resident in RAM ("Rss"),
the process's proportional share of this mapping ("Pss"),
the number of clean and dirty shared pages in the mapping,
and the number of clean and dirty private pages in the
mapping. "Referenced" indicates the amount of memory
currently marked as referenced or accessed. "Anonymous"
shows the amount of memory that does not belong to any
file. "Swap" shows how much would-be-anonymous memory is
also used, but out on swap.
The "KernelPageSize" line (available since Linux 2.6.29)
is the page size used by the kernel to back the virtual
memory area. This matches the size used by the MMU in the
majority of cases. However, one counter-example occurs on
PPC64 kernels whereby a kernel using 64 kB as a base page
size may still use 4 kB pages for the MMU on older
processors. To distinguish the two attributes, the
"MMUPageSize" line (also available since Linux 2.6.29)
reports the page size used by the MMU.
The "Locked" indicates whether the mapping is locked in
memory or not.
The "ProtectionKey" line (available since Linux 4.9, on
x86 only) contains the memory protection key (see
pkeys(7)) associated with the virtual memory area. This
entry is present only if the kernel was built with the
CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS configuration
option (since Linux 4.6).
The "VmFlags" line (available since Linux 3.8) represents
the kernel flags associated with the virtual memory area,
encoded using the following two-letter codes:
rd - readable
wr - writable
ex - executable
sh - shared
mr - may read
mw - may write
me - may execute
ms - may share
gd - stack segment grows down
pf - pure PFN range
dw - disabled write to the mapped file
lo - pages are locked in memory
io - memory mapped I/O area
sr - sequential read advise provided
rr - random read advise provided
dc - do not copy area on fork
de - do not expand area on remapping
ac - area is accountable
nr - swap space is not reserved for the area
ht - area uses huge tlb pages
sf - perform synchronous page faults (since Linux
4.15)
nl - non-linear mapping (removed in Linux 4.0)
ar - architecture specific flag
wf - wipe on fork (since Linux 4.14)
dd - do not include area into core dump
sd - soft-dirty flag (since Linux 3.13)
mm - mixed map area
hg - huge page advise flag
nh - no-huge page advise flag
mg - mergeable advise flag
um - userfaultfd missing pages tracking (since Linux
4.3)
uw - userfaultfd wprotect pages tracking (since Linux
4.3)
The /proc/[pid]/smaps file is present only if the
CONFIG_PROC_PAGE_MONITOR kernel configuration option is
enabled.
/proc/[pid]/stack (since Linux 2.6.29)
This file provides a symbolic trace of the function calls
in this process's kernel stack. This file is provided
only if the kernel was built with the CONFIG_STACKTRACE
configuration option.
Permission to access this file is governed by a ptrace
access mode PTRACE_MODE_ATTACH_FSCREDS check; see
ptrace(2).
/proc/[pid]/stat
Status information about the process. This is used by
ps(1). It is defined in the kernel source file
fs/proc/array.c.
The fields, in order, with their proper scanf(3) format
specifiers, are listed below. Whether or not certain of
these fields display valid information is governed by a
ptrace access mode PTRACE_MODE_READ_FSCREDS |
PTRACE_MODE_NOAUDIT check (refer to ptrace(2)). If the
check denies access, then the field value is displayed as
0. The affected fields are indicated with the marking
[PT].
(1) pid %d
The process ID.
(2) comm %s
The filename of the executable, in parentheses.
Strings longer than TASK_COMM_LEN (16) characters
(including the terminating null byte) are silently
truncated. This is visible whether or not the
executable is swapped out.
(3) state %c
One of the following characters, indicating process
state:
R Running
S Sleeping in an interruptible wait
D Waiting in uninterruptible disk sleep
Z Zombie
T Stopped (on a signal) or (before Linux 2.6.33)
trace stopped
t Tracing stop (Linux 2.6.33 onward)
W Paging (only before Linux 2.6.0)
X Dead (from Linux 2.6.0 onward)
x Dead (Linux 2.6.33 to 3.13 only)
K Wakekill (Linux 2.6.33 to 3.13 only)
W Waking (Linux 2.6.33 to 3.13 only)
P Parked (Linux 3.9 to 3.13 only)
(4) ppid %d
The PID of the parent of this process.
(5) pgrp %d
The process group ID of the process.
(6) session %d
The session ID of the process.
(7) tty_nr %d
The controlling terminal of the process. (The
minor device number is contained in the combination
of bits 31 to 20 and 7 to 0; the major device
number is in bits 15 to 8.)
(8) tpgid %d
The ID of the foreground process group of the
controlling terminal of the process.
(9) flags %u
The kernel flags word of the process. For bit
meanings, see the PF_* defines in the Linux kernel
source file include/linux/sched.h. Details depend
on the kernel version.
The format for this field was %lu before Linux 2.6.
(10) minflt %lu
The number of minor faults the process has made
which have not required loading a memory page from
disk.
(11) cminflt %lu
The number of minor faults that the process's
waited-for children have made.
(12) majflt %lu
The number of major faults the process has made
which have required loading a memory page from
disk.
(13) cmajflt %lu
The number of major faults that the process's
waited-for children have made.
(14) utime %lu
Amount of time that this process has been scheduled
in user mode, measured in clock ticks (divide by
sysconf(_SC_CLK_TCK)). This includes guest time,
guest_time (time spent running a virtual CPU, see
below), so that applications that are not aware of
the guest time field do not lose that time from
their calculations.
(15) stime %lu
Amount of time that this process has been scheduled
in kernel mode, measured in clock ticks (divide by
sysconf(_SC_CLK_TCK)).
(16) cutime %ld
Amount of time that this process's waited-for
children have been scheduled in user mode, measured
in clock ticks (divide by sysconf(_SC_CLK_TCK)).
(See also times(2).) This includes guest time,
cguest_time (time spent running a virtual CPU, see
below).
(17) cstime %ld
Amount of time that this process's waited-for
children have been scheduled in kernel mode,
measured in clock ticks (divide by
sysconf(_SC_CLK_TCK)).
(18) priority %ld
(Explanation for Linux 2.6) For processes running a
real-time scheduling policy (policy below; see
sched_setscheduler(2)), this is the negated
scheduling priority, minus one; that is, a number
in the range -2 to -100, corresponding to real-time
priorities 1 to 99. For processes running under a
non-real-time scheduling policy, this is the raw
nice value (setpriority(2)) as represented in the
kernel. The kernel stores nice values as numbers
in the range 0 (high) to 39 (low), corresponding to
the user-visible nice range of -20 to 19.
Before Linux 2.6, this was a scaled value based on
the scheduler weighting given to this process.
(19) nice %ld
The nice value (see setpriority(2)), a value in the
range 19 (low priority) to -20 (high priority).
(20) num_threads %ld
Number of threads in this process (since Linux
2.6). Before kernel 2.6, this field was hard coded
to 0 as a placeholder for an earlier removed field.
(21) itrealvalue %ld
The time in jiffies before the next SIGALRM is sent
to the process due to an interval timer. Since
kernel 2.6.17, this field is no longer maintained,
and is hard coded as 0.
(22) starttime %llu
The time the process started after system boot. In
kernels before Linux 2.6, this value was expressed
in jiffies. Since Linux 2.6, the value is
expressed in clock ticks (divide by
sysconf(_SC_CLK_TCK)).
The format for this field was %lu before Linux 2.6.
(23) vsize %lu
Virtual memory size in bytes.
(24) rss %ld
Resident Set Size: number of pages the process has
in real memory. This is just the pages which count
toward text, data, or stack space. This does not
include pages which have not been demand-loaded in,
or which are swapped out. This value is
inaccurate; see /proc/[pid]/statm below.
(25) rsslim %lu
Current soft limit in bytes on the rss of the
process; see the description of RLIMIT_RSS in
getrlimit(2).
(26) startcode %lu [PT]
The address above which program text can run.
(27) endcode %lu [PT]
The address below which program text can run.
(28) startstack %lu [PT]
The address of the start (i.e., bottom) of the
stack.
(29) kstkesp %lu [PT]
The current value of ESP (stack pointer), as found
in the kernel stack page for the process.
(30) kstkeip %lu [PT]
The current EIP (instruction pointer).
(31) signal %lu
The bitmap of pending signals, displayed as a
decimal number. Obsolete, because it does not
provide information on real-time signals; use
/proc/[pid]/status instead.
(32) blocked %lu
The bitmap of blocked signals, displayed as a
decimal number. Obsolete, because it does not
provide information on real-time signals; use
/proc/[pid]/status instead.
(33) sigignore %lu
The bitmap of ignored signals, displayed as a
decimal number. Obsolete, because it does not
provide information on real-time signals; use
/proc/[pid]/status instead.
(34) sigcatch %lu
The bitmap of caught signals, displayed as a
decimal number. Obsolete, because it does not
provide information on real-time signals; use
/proc/[pid]/status instead.
(35) wchan %lu [PT]
This is the "channel" in which the process is
waiting. It is the address of a location in the
kernel where the process is sleeping. The
corresponding symbolic name can be found in
/proc/[pid]/wchan.
(36) nswap %lu
Number of pages swapped (not maintained).
(37) cnswap %lu
Cumulative nswap for child processes (not
maintained).
(38) exit_signal %d (since Linux 2.1.22)
Signal to be sent to parent when we die.
(39) processor %d (since Linux 2.2.8)
CPU number last executed on.
(40) rt_priority %u (since Linux 2.5.19)
Real-time scheduling priority, a number in the
range 1 to 99 for processes scheduled under a real-
time policy, or 0, for non-real-time processes (see
sched_setscheduler(2)).
(41) policy %u (since Linux 2.5.19)
Scheduling policy (see sched_setscheduler(2)).
Decode using the SCHED_* constants in
linux/sched.h.
The format for this field was %lu before Linux
2.6.22.
(42) delayacct_blkio_ticks %llu (since Linux 2.6.18)
Aggregated block I/O delays, measured in clock
ticks (centiseconds).
(43) guest_time %lu (since Linux 2.6.24)
Guest time of the process (time spent running a
virtual CPU for a guest operating system), measured
in clock ticks (divide by sysconf(_SC_CLK_TCK)).
(44) cguest_time %ld (since Linux 2.6.24)
Guest time of the process's children, measured in
clock ticks (divide by sysconf(_SC_CLK_TCK)).
(45) start_data %lu (since Linux 3.3) [PT]
Address above which program initialized and
uninitialized (BSS) data are placed.
(46) end_data %lu (since Linux 3.3) [PT]
Address below which program initialized and
uninitialized (BSS) data are placed.
(47) start_brk %lu (since Linux 3.3) [PT]
Address above which program heap can be expanded
with brk(2).
(48) arg_start %lu (since Linux 3.5) [PT]
Address above which program command-line arguments
(argv) are placed.
(49) arg_end %lu (since Linux 3.5) [PT]
Address below program command-line arguments (argv)
are placed.
(50) env_start %lu (since Linux 3.5) [PT]
Address above which program environment is placed.
(51) env_end %lu (since Linux 3.5) [PT]
Address below which program environment is placed.
(52) exit_code %d (since Linux 3.5) [PT]
The thread's exit status in the form reported by
waitpid(2).
/proc/[pid]/statm
Provides information about memory usage, measured in
pages. The columns are:
size (1) total program size
(same as VmSize in /proc/[pid]/status)
resident (2) resident set size
(inaccurate; same as VmRSS in /proc/[pid]/status)
shared (3) number of resident shared pages
(i.e., backed by a file)
(inaccurate; same as RssFile+RssShmem in
/proc/[pid]/status)
text (4) text (code)
lib (5) library (unused since Linux 2.6; always 0)
data (6) data + stack
dt (7) dirty pages (unused since Linux 2.6; always 0)
Some of these values are inaccurate because of a kernel-
internal scalability optimization. If accurate values are
required, use /proc/[pid]/smaps or
/proc/[pid]/smaps_rollup instead, which are much slower
but provide accurate, detailed information.
/proc/[pid]/status
Provides much of the information in /proc/[pid]/stat and
/proc/[pid]/statm in a format that's easier for humans to
parse. Here's an example:
$ cat /proc/$$/status
Name: bash
Umask: 0022
State: S (sleeping)
Tgid: 17248
Ngid: 0
Pid: 17248
PPid: 17200
TracerPid: 0
Uid: 1000 1000 1000 1000
Gid: 100 100 100 100
FDSize: 256
Groups: 16 33 100
NStgid: 17248
NSpid: 17248
NSpgid: 17248
NSsid: 17200
VmPeak: 131168 kB
VmSize: 131168 kB
VmLck: 0 kB
VmPin: 0 kB
VmHWM: 13484 kB
VmRSS: 13484 kB
RssAnon: 10264 kB
RssFile: 3220 kB
RssShmem: 0 kB
VmData: 10332 kB
VmStk: 136 kB
VmExe: 992 kB
VmLib: 2104 kB
VmPTE: 76 kB
VmPMD: 12 kB
VmSwap: 0 kB
HugetlbPages: 0 kB # 4.4
CoreDumping: 0 # 4.15
Threads: 1
SigQ: 0/3067
SigPnd: 0000000000000000
ShdPnd: 0000000000000000
SigBlk: 0000000000010000
SigIgn: 0000000000384004
SigCgt: 000000004b813efb
CapInh: 0000000000000000
CapPrm: 0000000000000000
CapEff: 0000000000000000
CapBnd: ffffffffffffffff
CapAmb: 0000000000000000
NoNewPrivs: 0
Seccomp: 0
Speculation_Store_Bypass: vulnerable
Cpus_allowed: 00000001
Cpus_allowed_list: 0
Mems_allowed: 1
Mems_allowed_list: 0
voluntary_ctxt_switches: 150
nonvoluntary_ctxt_switches: 545
The fields are as follows:
Name Command run by this process. Strings longer than
TASK_COMM_LEN (16) characters (including the
terminating null byte) are silently truncated.
Umask Process umask, expressed in octal with a leading
zero; see umask(2). (Since Linux 4.7.)
State Current state of the process. One of "R
(running)", "S (sleeping)", "D (disk sleep)", "T
(stopped)", "t (tracing stop)", "Z (zombie)", or "X
(dead)".
Tgid Thread group ID (i.e., Process ID).
Ngid NUMA group ID (0 if none; since Linux 3.13).
Pid Thread ID (see gettid(2)).
PPid PID of parent process.
TracerPid
PID of process tracing this process (0 if not being
traced).
Uid, Gid
Real, effective, saved set, and filesystem UIDs
(GIDs).
FDSize Number of file descriptor slots currently
allocated.
Groups Supplementary group list.
NStgid Thread group ID (i.e., PID) in each of the PID
namespaces of which [pid] is a member. The
leftmost entry shows the value with respect to the
PID namespace of the process that mounted this
procfs (or the root namespace if mounted by the
kernel), followed by the value in successively
nested inner namespaces. (Since Linux 4.1.)
NSpid Thread ID in each of the PID namespaces of which
[pid] is a member. The fields are ordered as for
NStgid. (Since Linux 4.1.)
NSpgid Process group ID in each of the PID namespaces of
which [pid] is a member. The fields are ordered as
for NStgid. (Since Linux 4.1.)
NSsid descendant namespace session ID hierarchy Session
ID in each of the PID namespaces of which [pid] is
a member. The fields are ordered as for NStgid.
(Since Linux 4.1.)
VmPeak Peak virtual memory size.
VmSize Virtual memory size.
VmLck Locked memory size (see mlock(2)).
VmPin Pinned memory size (since Linux 3.2). These are
pages that can't be moved because something needs
to directly access physical memory.
VmHWM Peak resident set size ("high water mark"). This
value is inaccurate; see /proc/[pid]/statm above.
VmRSS Resident set size. Note that the value here is the
sum of RssAnon, RssFile, and RssShmem. This value
is inaccurate; see /proc/[pid]/statm above.
RssAnon
Size of resident anonymous memory. (since Linux
4.5). This value is inaccurate; see
/proc/[pid]/statm above.
RssFile
Size of resident file mappings. (since Linux 4.5).
This value is inaccurate; see /proc/[pid]/statm
above.
RssShmem
Size of resident shared memory (includes System V
shared memory, mappings from tmpfs(5), and shared
anonymous mappings). (since Linux 4.5).
VmData, VmStk, VmExe
Size of data, stack, and text segments. This value
is inaccurate; see /proc/[pid]/statm above.
VmLib Shared library code size.
VmPTE Page table entries size (since Linux 2.6.10).
VmPMD Size of second-level page tables (added in Linux
4.0; removed in Linux 4.15).
VmSwap Swapped-out virtual memory size by anonymous
private pages; shmem swap usage is not included
(since Linux 2.6.34). This value is inaccurate;
see /proc/[pid]/statm above.
HugetlbPages
Size of hugetlb memory portions (since Linux 4.4).
CoreDumping
Contains the value 1 if the process is currently
dumping core, and 0 if it is not (since Linux
4.15). This information can be used by a
monitoring process to avoid killing a process that
is currently dumping core, which could result in a
corrupted core dump file.
Threads
Number of threads in process containing this
thread.
SigQ This field contains two slash-separated numbers
that relate to queued signals for the real user ID
of this process. The first of these is the number
of currently queued signals for this real user ID,
and the second is the resource limit on the number
of queued signals for this process (see the
description of RLIMIT_SIGPENDING in getrlimit(2)).
SigPnd, ShdPnd
Mask (expressed in hexadecimal) of signals pending
for thread and for process as a whole (see
pthreads(7) and signal(7)).
SigBlk, SigIgn, SigCgt
Masks (expressed in hexadecimal) indicating signals
being blocked, ignored, and caught (see signal(7)).
CapInh, CapPrm, CapEff
Masks (expressed in hexadecimal) of capabilities
enabled in inheritable, permitted, and effective
sets (see capabilities(7)).
CapBnd Capability bounding set, expressed in hexadecimal
(since Linux 2.6.26, see capabilities(7)).
CapAmb Ambient capability set, expressed in hexadecimal
(since Linux 4.3, see capabilities(7)).
NoNewPrivs
Value of the no_new_privs bit (since Linux 4.10,
see prctl(2)).
Seccomp
Seccomp mode of the process (since Linux 3.8, see
seccomp(2)). 0 means SECCOMP_MODE_DISABLED; 1
means SECCOMP_MODE_STRICT; 2 means
SECCOMP_MODE_FILTER. This field is provided only
if the kernel was built with the CONFIG_SECCOMP
kernel configuration option enabled.
Speculation_Store_Bypass
Speculation flaw mitigation state (since Linux
4.17, see prctl(2)).
Cpus_allowed
Hexadecimal mask of CPUs on which this process may
run (since Linux 2.6.24, see cpuset(7)).
Cpus_allowed_list
Same as previous, but in "list format" (since Linux
2.6.26, see cpuset(7)).
Mems_allowed
Mask of memory nodes allowed to this process (since
Linux 2.6.24, see cpuset(7)).
Mems_allowed_list
Same as previous, but in "list format" (since Linux
2.6.26, see cpuset(7)).
voluntary_ctxt_switches, nonvoluntary_ctxt_switches
Number of voluntary and involuntary context
switches (since Linux 2.6.23).
/proc/[pid]/syscall (since Linux 2.6.27)
This file exposes the system call number and argument
registers for the system call currently being executed by
the process, followed by the values of the stack pointer
and program counter registers. The values of all six
argument registers are exposed, although most system calls
use fewer registers.
If the process is blocked, but not in a system call, then
the file displays -1 in place of the system call number,
followed by just the values of the stack pointer and
program counter. If process is not blocked, then the file
contains just the string "running".
This file is present only if the kernel was configured
with CONFIG_HAVE_ARCH_TRACEHOOK.
Permission to access this file is governed by a ptrace
access mode PTRACE_MODE_ATTACH_FSCREDS check; see
ptrace(2).
/proc/[pid]/task (since Linux 2.6.0)
This is a directory that contains one subdirectory for
each thread in the process. The name of each subdirectory
is the numerical thread ID ([tid]) of the thread (see
gettid(2)).
Within each of these subdirectories, there is a set of
files with the same names and contents as under the
/proc/[pid] directories. For attributes that are shared
by all threads, the contents for each of the files under
the task/[tid] subdirectories will be the same as in the
corresponding file in the parent /proc/[pid] directory
(e.g., in a multithreaded process, all of the
task/[tid]/cwd files will have the same value as the
/proc/[pid]/cwd file in the parent directory, since all of
the threads in a process share a working directory). For
attributes that are distinct for each thread, the
corresponding files under task/[tid] may have different
values (e.g., various fields in each of the
task/[tid]/status files may be different for each thread),
or they might not exist in /proc/[pid] at all.
In a multithreaded process, the contents of the
/proc/[pid]/task directory are not available if the main
thread has already terminated (typically by calling
pthread_exit(3)).
/proc/[pid]/task/[tid]/children (since Linux 3.5)
A space-separated list of child tasks of this task. Each
child task is represented by its TID.
This option is intended for use by the checkpoint-restore
(CRIU) system, and reliably provides a list of children
only if all of the child processes are stopped or frozen.
It does not work properly if children of the target task
exit while the file is being read! Exiting children may
cause non-exiting children to be omitted from the list.
This makes this interface even more unreliable than
classic PID-based approaches if the inspected task and its
children aren't frozen, and most code should probably not
use this interface.
Until Linux 4.2, the presence of this file was governed by
the CONFIG_CHECKPOINT_RESTORE kernel configuration option.
Since Linux 4.2, it is governed by the
CONFIG_PROC_CHILDREN option.
/proc/[pid]/timers (since Linux 3.10)
A list of the POSIX timers for this process. Each timer
is listed with a line that starts with the string "ID:".
For example:
ID: 1
signal: 60/00007fff86e452a8
notify: signal/pid.2634
ClockID: 0
ID: 0
signal: 60/00007fff86e452a8
notify: signal/pid.2634
ClockID: 1
The lines shown for each timer have the following
meanings:
ID The ID for this timer. This is not the same as the
timer ID returned by timer_create(2); rather, it is
the same kernel-internal ID that is available via
the si_timerid field of the siginfo_t structure
(see sigaction(2)).
signal This is the signal number that this timer uses to
deliver notifications followed by a slash, and then
the sigev_value value supplied to the signal
handler. Valid only for timers that notify via a
signal.
notify The part before the slash specifies the mechanism
that this timer uses to deliver notifications, and
is one of "thread", "signal", or "none".
Immediately following the slash is either the
string "tid" for timers with SIGEV_THREAD_ID
notification, or "pid" for timers that notify by
other mechanisms. Following the "." is the PID of
the process (or the kernel thread ID of the thread)
that will be delivered a signal if the timer
delivers notifications via a signal.
ClockID
This field identifies the clock that the timer uses
for measuring time. For most clocks, this is a
number that matches one of the user-space CLOCK_*
constants exposed via <time.h>.
CLOCK_PROCESS_CPUTIME_ID timers display with a
value of -6 in this field. CLOCK_THREAD_CPUTIME_ID
timers display with a value of -2 in this field.
This file is available only when the kernel was configured
with CONFIG_CHECKPOINT_RESTORE.
/proc/[pid]/timerslack_ns (since Linux 4.6)
This file exposes the process's "current" timer slack
value, expressed in nanoseconds. The file is writable,
allowing the process's timer slack value to be changed.
Writing 0 to this file resets the "current" timer slack to
the "default" timer slack value. For further details, see
the discussion of PR_SET_TIMERSLACK in prctl(2).
Initially, permission to access this file was governed by
a ptrace access mode PTRACE_MODE_ATTACH_FSCREDS check (see
ptrace(2)). However, this was subsequently deemed too
strict a requirement (and had the side effect that
requiring a process to have the CAP_SYS_PTRACE capability
would also allow it to view and change any process's
memory). Therefore, since Linux 4.9, only the (weaker)
CAP_SYS_NICE capability is required to access this file.
/proc/[pid]/uid_map (since Linux 3.5)
See user_namespaces(7).
/proc/[pid]/wchan (since Linux 2.6.0)
The symbolic name corresponding to the location in the
kernel where the process is sleeping.
Permission to access this file is governed by a ptrace
access mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).
/proc/[tid]
There is a numerical subdirectory for each running thread
that is not a thread group leader (i.e., a thread whose
thread ID is not the same as its process ID); the
subdirectory is named by the thread ID. Each one of these
subdirectories contains files and subdirectories exposing
information about the thread with the thread ID tid. The
contents of these directories are the same as the
corresponding /proc/[pid]/task/[tid] directories.
The /proc/[tid] subdirectories are not visible when
iterating through /proc with getdents(2) (and thus are not
visible when one uses ls(1) to view the contents of
/proc). However, the pathnames of these directories are
visible to (i.e., usable as arguments in) system calls
that operate on pathnames.
/proc/apm
Advanced power management version and battery information
when CONFIG_APM is defined at kernel compilation time.
/proc/buddyinfo
This file contains information which is used for
diagnosing memory fragmentation issues. Each line starts
with the identification of the node and the name of the
zone which together identify a memory region. This is
then followed by the count of available chunks of a
certain order in which these zones are split. The size in
bytes of a certain order is given by the formula:
(2^order) * PAGE_SIZE
The binary buddy allocator algorithm inside the kernel
will split one chunk into two chunks of a smaller order
(thus with half the size) or combine two contiguous chunks
into one larger chunk of a higher order (thus with double
the size) to satisfy allocation requests and to counter
memory fragmentation. The order matches the column
number, when starting to count at zero.
For example on an x86-64 system:
Node 0, zone DMA 1 1 1 0 2 1 1 0 1 1 3
Node 0, zone DMA32 65 47 4 81 52 28 13 10 5 1 404
Node 0, zone Normal 216 55 189 101 84 38 37 27 5 3 587
In this example, there is one node containing three zones
and there are 11 different chunk sizes. If the page size
is 4 kilobytes, then the first zone called DMA (on x86 the
first 16 megabyte of memory) has 1 chunk of 4 kilobytes
(order 0) available and has 3 chunks of 4 megabytes (order
10) available.
If the memory is heavily fragmented, the counters for
higher order chunks will be zero and allocation of large
contiguous areas will fail.
Further information about the zones can be found in
/proc/zoneinfo.
/proc/bus
Contains subdirectories for installed busses.
/proc/bus/pccard
Subdirectory for PCMCIA devices when CONFIG_PCMCIA is set
at kernel compilation time.
/proc/bus/pccard/drivers
/proc/bus/pci
Contains various bus subdirectories and pseudo-files
containing information about PCI busses, installed
devices, and device drivers. Some of these files are not
ASCII.
/proc/bus/pci/devices
Information about PCI devices. They may be accessed
through lspci(8) and setpci(8).
/proc/cgroups (since Linux 2.6.24)
See cgroups(7).
/proc/cmdline
Arguments passed to the Linux kernel at boot time. Often
done via a boot manager such as lilo(8) or grub(8).
/proc/config.gz (since Linux 2.6)
This file exposes the configuration options that were used
to build the currently running kernel, in the same format
as they would be shown in the .config file that resulted
when configuring the kernel (using make xconfig, make
config, or similar). The file contents are compressed;
view or search them using zcat(1) and zgrep(1). As long
as no changes have been made to the following file, the
contents of /proc/config.gz are the same as those provided
by:
cat /lib/modules/$(uname -r)/build/.config
/proc/config.gz is provided only if the kernel is
configured with CONFIG_IKCONFIG_PROC.
/proc/crypto
A list of the ciphers provided by the kernel crypto API.
For details, see the kernel Linux Kernel Crypto API
documentation available under the kernel source directory
Documentation/crypto/ (or Documentation/DocBook before
4.10; the documentation can be built using a command such
as make htmldocs in the root directory of the kernel
source tree).
/proc/cpuinfo
This is a collection of CPU and system architecture
dependent items, for each supported architecture a
different list. Two common entries are processor which
gives CPU number and bogomips; a system constant that is
calculated during kernel initialization. SMP machines
have information for each CPU. The lscpu(1) command
gathers its information from this file.
/proc/devices
Text listing of major numbers and device groups. This can
be used by MAKEDEV scripts for consistency with the
kernel.
/proc/diskstats (since Linux 2.5.69)
This file contains disk I/O statistics for each disk
device. See the Linux kernel source file
Documentation/iostats.txt for further information.
/proc/dma
This is a list of the registered ISA DMA (direct memory
access) channels in use.
/proc/driver
Empty subdirectory.
/proc/execdomains
List of the execution domains (ABI personalities).
/proc/fb
Frame buffer information when CONFIG_FB is defined during
kernel compilation.
/proc/filesystems
A text listing of the filesystems which are supported by
the kernel, namely filesystems which were compiled into
the kernel or whose kernel modules are currently loaded.
(See also filesystems(5).) If a filesystem is marked with
"nodev", this means that it does not require a block
device to be mounted (e.g., virtual filesystem, network
filesystem).
Incidentally, this file may be used by mount(8) when no
filesystem is specified and it didn't manage to determine
the filesystem type. Then filesystems contained in this
file are tried (excepted those that are marked with
"nodev").
/proc/fs
Contains subdirectories that in turn contain files with
information about (certain) mounted filesystems.
/proc/ide
This directory exists on systems with the IDE bus. There
are directories for each IDE channel and attached device.
Files include:
cache buffer size in KB
capacity number of sectors
driver driver version
geometry physical and logical geometry
identify in hexadecimal
media media type
model manufacturer's model number
settings drive settings
smart_thresholds IDE disk management thresholds (in hex)
smart_values IDE disk management values (in hex)
The hdparm(8) utility provides access to this information
in a friendly format.
/proc/interrupts
This is used to record the number of interrupts per CPU
per IO device. Since Linux 2.6.24, for the i386 and
x86-64 architectures, at least, this also includes
interrupts internal to the system (that is, not associated
with a device as such), such as NMI (nonmaskable
interrupt), LOC (local timer interrupt), and for SMP
systems, TLB (TLB flush interrupt), RES (rescheduling
interrupt), CAL (remote function call interrupt), and
possibly others. Very easy to read formatting, done in
ASCII.
/proc/iomem
I/O memory map in Linux 2.4.
/proc/ioports
This is a list of currently registered Input-Output port
regions that are in use.
/proc/kallsyms (since Linux 2.5.71)
This holds the kernel exported symbol definitions used by
the modules(X) tools to dynamically link and bind loadable
modules. In Linux 2.5.47 and earlier, a similar file with
slightly different syntax was named ksyms.
/proc/kcore
This file represents the physical memory of the system and
is stored in the ELF core file format. With this pseudo-
file, and an unstripped kernel (/usr/src/linux/vmlinux)
binary, GDB can be used to examine the current state of
any kernel data structures.
The total length of the file is the size of physical
memory (RAM) plus 4 KiB.
/proc/keys (since Linux 2.6.10)
See keyrings(7).
/proc/key-users (since Linux 2.6.10)
See keyrings(7).
/proc/kmsg
This file can be used instead of the syslog(2) system call
to read kernel messages. A process must have superuser
privileges to read this file, and only one process should
read this file. This file should not be read if a syslog
process is running which uses the syslog(2) system call
facility to log kernel messages.
Information in this file is retrieved with the dmesg(1)
program.
/proc/kpagecgroup (since Linux 4.3)
This file contains a 64-bit inode number of the memory
cgroup each page is charged to, indexed by page frame
number (see the discussion of /proc/[pid]/pagemap).
The /proc/kpagecgroup file is present only if the
CONFIG_MEMCG kernel configuration option is enabled.
/proc/kpagecount (since Linux 2.6.25)
This file contains a 64-bit count of the number of times
each physical page frame is mapped, indexed by page frame
number (see the discussion of /proc/[pid]/pagemap).
The /proc/kpagecount file is present only if the
CONFIG_PROC_PAGE_MONITOR kernel configuration option is
enabled.
/proc/kpageflags (since Linux 2.6.25)
This file contains 64-bit masks corresponding to each
physical page frame; it is indexed by page frame number
(see the discussion of /proc/[pid]/pagemap). The bits are
as follows:
0 - KPF_LOCKED
1 - KPF_ERROR
2 - KPF_REFERENCED
3 - KPF_UPTODATE
4 - KPF_DIRTY
5 - KPF_LRU
6 - KPF_ACTIVE
7 - KPF_SLAB
8 - KPF_WRITEBACK
9 - KPF_RECLAIM
10 - KPF_BUDDY
11 - KPF_MMAP (since Linux 2.6.31)
12 - KPF_ANON (since Linux 2.6.31)
13 - KPF_SWAPCACHE (since Linux 2.6.31)
14 - KPF_SWAPBACKED (since Linux 2.6.31)
15 - KPF_COMPOUND_HEAD (since Linux 2.6.31)
16 - KPF_COMPOUND_TAIL (since Linux 2.6.31)
17 - KPF_HUGE (since Linux 2.6.31)
18 - KPF_UNEVICTABLE (since Linux 2.6.31)
19 - KPF_HWPOISON (since Linux 2.6.31)
20 - KPF_NOPAGE (since Linux 2.6.31)
21 - KPF_KSM (since Linux 2.6.32)
22 - KPF_THP (since Linux 3.4)
23 - KPF_BALLOON (since Linux 3.18)
24 - KPF_ZERO_PAGE (since Linux 4.0)
25 - KPF_IDLE (since Linux 4.3)
For further details on the meanings of these bits, see the
kernel source file
Documentation/admin-guide/mm/pagemap.rst. Before kernel
2.6.29, KPF_WRITEBACK, KPF_RECLAIM, KPF_BUDDY, and
KPF_LOCKED did not report correctly.
The /proc/kpageflags file is present only if the
CONFIG_PROC_PAGE_MONITOR kernel configuration option is
enabled.
/proc/ksyms (Linux 1.1.23–2.5.47)
See /proc/kallsyms.
/proc/loadavg
The first three fields in this file are load average
figures giving the number of jobs in the run queue (state
R) or waiting for disk I/O (state D) averaged over 1, 5,
and 15 minutes. They are the same as the load average
numbers given by uptime(1) and other programs. The fourth
field consists of two numbers separated by a slash (/).
The first of these is the number of currently runnable
kernel scheduling entities (processes, threads). The
value after the slash is the number of kernel scheduling
entities that currently exist on the system. The fifth
field is the PID of the process that was most recently
created on the system.
/proc/locks
This file shows current file locks (flock(2) and fcntl(2))
and leases (fcntl(2)).
An example of the content shown in this file is the
following:
1: POSIX ADVISORY READ 5433 08:01:7864448 128 128
2: FLOCK ADVISORY WRITE 2001 08:01:7864554 0 EOF
3: FLOCK ADVISORY WRITE 1568 00:2f:32388 0 EOF
4: POSIX ADVISORY WRITE 699 00:16:28457 0 EOF
5: POSIX ADVISORY WRITE 764 00:16:21448 0 0
6: POSIX ADVISORY READ 3548 08:01:7867240 1 1
7: POSIX ADVISORY READ 3548 08:01:7865567 1826 2335
8: OFDLCK ADVISORY WRITE -1 08:01:8713209 128 191
The fields shown in each line are as follows:
(1) The ordinal position of the lock in the list.
(2) The lock type. Values that may appear here include:
FLOCK This is a BSD file lock created using flock(2).
OFDLCK This is an open file description (OFD) lock
created using fcntl(2).
POSIX This is a POSIX byte-range lock created using
fcntl(2).
(3) Among the strings that can appear here are the
following:
ADVISORY
This is an advisory lock.
MANDATORY
This is a mandatory lock.
(4) The type of lock. Values that can appear here are:
READ This is a POSIX or OFD read lock, or a BSD
shared lock.
WRITE This is a POSIX or OFD write lock, or a BSD
exclusive lock.
(5) The PID of the process that owns the lock.
Because OFD locks are not owned by a single process
(since multiple processes may have file descriptors
that refer to the same open file description), the
value -1 is displayed in this field for OFD locks.
(Before kernel 4.14, a bug meant that the PID of the
process that initially acquired the lock was displayed
instead of the value -1.)
(6) Three colon-separated subfields that identify the
major and minor device ID of the device containing the
filesystem where the locked file resides, followed by
the inode number of the locked file.
(7) The byte offset of the first byte of the lock. For
BSD locks, this value is always 0.
(8) The byte offset of the last byte of the lock. EOF in
this field means that the lock extends to the end of
the file. For BSD locks, the value shown is always
EOF.
Since Linux 4.9, the list of locks shown in /proc/locks is
filtered to show just the locks for the processes in the
PID namespace (see pid_namespaces(7)) for which the /proc
filesystem was mounted. (In the initial PID namespace,
there is no filtering of the records shown in this file.)
The lslocks(8) command provides a bit more information
about each lock.
/proc/malloc (only up to and including Linux 2.2)
This file is present only if CONFIG_DEBUG_MALLOC was
defined during compilation.
/proc/meminfo
This file reports statistics about memory usage on the
system. It is used by free(1) to report the amount of
free and used memory (both physical and swap) on the
system as well as the shared memory and buffers used by
the kernel. Each line of the file consists of a parameter
name, followed by a colon, the value of the parameter, and
an option unit of measurement (e.g., "kB"). The list
below describes the parameter names and the format
specifier required to read the field value. Except as
noted below, all of the fields have been present since at
least Linux 2.6.0. Some fields are displayed only if the
kernel was configured with various options; those
dependencies are noted in the list.
MemTotal %lu
Total usable RAM (i.e., physical RAM minus a few
reserved bits and the kernel binary code).
MemFree %lu
The sum of LowFree+HighFree.
MemAvailable %lu (since Linux 3.14)
An estimate of how much memory is available for
starting new applications, without swapping.
Buffers %lu
Relatively temporary storage for raw disk blocks
that shouldn't get tremendously large (20 MB or
so).
Cached %lu
In-memory cache for files read from the disk (the
page cache). Doesn't include SwapCached.
SwapCached %lu
Memory that once was swapped out, is swapped back
in but still also is in the swap file. (If memory
pressure is high, these pages don't need to be
swapped out again because they are already in the
swap file. This saves I/O.)
Active %lu
Memory that has been used more recently and usually
not reclaimed unless absolutely necessary.
Inactive %lu
Memory which has been less recently used. It is
more eligible to be reclaimed for other purposes.
Active(anon) %lu (since Linux 2.6.28)
[To be documented.]
Inactive(anon) %lu (since Linux 2.6.28)
[To be documented.]
Active(file) %lu (since Linux 2.6.28)
[To be documented.]
Inactive(file) %lu (since Linux 2.6.28)
[To be documented.]
Unevictable %lu (since Linux 2.6.28)
(From Linux 2.6.28 to 2.6.30,
CONFIG_UNEVICTABLE_LRU was required.) [To be
documented.]
Mlocked %lu (since Linux 2.6.28)
(From Linux 2.6.28 to 2.6.30,
CONFIG_UNEVICTABLE_LRU was required.) [To be
documented.]
HighTotal %lu
(Starting with Linux 2.6.19, CONFIG_HIGHMEM is
required.) Total amount of highmem. Highmem is
all memory above ~860 MB of physical memory.
Highmem areas are for use by user-space programs,
or for the page cache. The kernel must use tricks
to access this memory, making it slower to access
than lowmem.
HighFree %lu
(Starting with Linux 2.6.19, CONFIG_HIGHMEM is
required.) Amount of free highmem.
LowTotal %lu
(Starting with Linux 2.6.19, CONFIG_HIGHMEM is
required.) Total amount of lowmem. Lowmem is
memory which can be used for everything that
highmem can be used for, but it is also available
for the kernel's use for its own data structures.
Among many other things, it is where everything
from Slab is allocated. Bad things happen when
you're out of lowmem.
LowFree %lu
(Starting with Linux 2.6.19, CONFIG_HIGHMEM is
required.) Amount of free lowmem.
MmapCopy %lu (since Linux 2.6.29)
(CONFIG_MMU is required.) [To be documented.]
SwapTotal %lu
Total amount of swap space available.
SwapFree %lu
Amount of swap space that is currently unused.
Dirty %lu
Memory which is waiting to get written back to the
disk.
Writeback %lu
Memory which is actively being written back to the
disk.
AnonPages %lu (since Linux 2.6.18)
Non-file backed pages mapped into user-space page
tables.
Mapped %lu
Files which have been mapped into memory (with
mmap(2)), such as libraries.
Shmem %lu (since Linux 2.6.32)
Amount of memory consumed in tmpfs(5) filesystems.
KReclaimable %lu (since Linux 4.20)
Kernel allocations that the kernel will attempt to
reclaim under memory pressure. Includes
SReclaimable (below), and other direct allocations
with a shrinker.
Slab %lu
In-kernel data structures cache. (See
slabinfo(5).)
SReclaimable %lu (since Linux 2.6.19)
Part of Slab, that might be reclaimed, such as
caches.
SUnreclaim %lu (since Linux 2.6.19)
Part of Slab, that cannot be reclaimed on memory
pressure.
KernelStack %lu (since Linux 2.6.32)
Amount of memory allocated to kernel stacks.
PageTables %lu (since Linux 2.6.18)
Amount of memory dedicated to the lowest level of
page tables.
Quicklists %lu (since Linux 2.6.27)
(CONFIG_QUICKLIST is required.) [To be
documented.]
NFS_Unstable %lu (since Linux 2.6.18)
NFS pages sent to the server, but not yet committed
to stable storage.
Bounce %lu (since Linux 2.6.18)
Memory used for block device "bounce buffers".
WritebackTmp %lu (since Linux 2.6.26)
Memory used by FUSE for temporary writeback
buffers.
CommitLimit %lu (since Linux 2.6.10)
This is the total amount of memory currently
available to be allocated on the system, expressed
in kilobytes. This limit is adhered to only if
strict overcommit accounting is enabled (mode 2 in
/proc/sys/vm/overcommit_memory). The limit is
calculated according to the formula described under
/proc/sys/vm/overcommit_memory. For further
details, see the kernel source file
Documentation/vm/overcommit-accounting.rst.
Committed_AS %lu
The amount of memory presently allocated on the
system. The committed memory is a sum of all of
the memory which has been allocated by processes,
even if it has not been "used" by them as of yet.
A process which allocates 1 GB of memory (using
malloc(3) or similar), but touches only 300 MB of
that memory will show up as using only 300 MB of
memory even if it has the address space allocated
for the entire 1 GB.
This 1 GB is memory which has been "committed" to
by the VM and can be used at any time by the
allocating application. With strict overcommit
enabled on the system (mode 2 in
/proc/sys/vm/overcommit_memory), allocations which
would exceed the CommitLimit will not be permitted.
This is useful if one needs to guarantee that
processes will not fail due to lack of memory once
that memory has been successfully allocated.
VmallocTotal %lu
Total size of vmalloc memory area.
VmallocUsed %lu
Amount of vmalloc area which is used. Since Linux
4.4, this field is no longer calculated, and is
hard coded as 0. See /proc/vmallocinfo.
VmallocChunk %lu
Largest contiguous block of vmalloc area which is
free. Since Linux 4.4, this field is no longer
calculated and is hard coded as 0. See
/proc/vmallocinfo.
HardwareCorrupted %lu (since Linux 2.6.32)
(CONFIG_MEMORY_FAILURE is required.) [To be
documented.]
LazyFree %lu (since Linux 4.12)
Shows the amount of memory marked by madvise(2)
MADV_FREE.
AnonHugePages %lu (since Linux 2.6.38)
(CONFIG_TRANSPARENT_HUGEPAGE is required.) Non-
file backed huge pages mapped into user-space page
tables.
ShmemHugePages %lu (since Linux 4.8)
(CONFIG_TRANSPARENT_HUGEPAGE is required.) Memory
used by shared memory (shmem) and tmpfs(5)
allocated with huge pages.
ShmemPmdMapped %lu (since Linux 4.8)
(CONFIG_TRANSPARENT_HUGEPAGE is required.) Shared
memory mapped into user space with huge pages.
CmaTotal %lu (since Linux 3.1)
Total CMA (Contiguous Memory Allocator) pages.
(CONFIG_CMA is required.)
CmaFree %lu (since Linux 3.1)
Free CMA (Contiguous Memory Allocator) pages.
(CONFIG_CMA is required.)
HugePages_Total %lu
(CONFIG_HUGETLB_PAGE is required.) The size of the
pool of huge pages.
HugePages_Free %lu
(CONFIG_HUGETLB_PAGE is required.) The number of
huge pages in the pool that are not yet allocated.
HugePages_Rsvd %lu (since Linux 2.6.17)
(CONFIG_HUGETLB_PAGE is required.) This is the
number of huge pages for which a commitment to
allocate from the pool has been made, but no
allocation has yet been made. These reserved huge
pages guarantee that an application will be able to
allocate a huge page from the pool of huge pages at
fault time.
HugePages_Surp %lu (since Linux 2.6.24)
(CONFIG_HUGETLB_PAGE is required.) This is the
number of huge pages in the pool above the value in
/proc/sys/vm/nr_hugepages. The maximum number of
surplus huge pages is controlled by
/proc/sys/vm/nr_overcommit_hugepages.
Hugepagesize %lu
(CONFIG_HUGETLB_PAGE is required.) The size of
huge pages.
DirectMap4k %lu (since Linux 2.6.27)
Number of bytes of RAM linearly mapped by kernel in
4 kB pages. (x86.)
DirectMap4M %lu (since Linux 2.6.27)
Number of bytes of RAM linearly mapped by kernel in
4 MB pages. (x86 with CONFIG_X86_64 or
CONFIG_X86_PAE enabled.)
DirectMap2M %lu (since Linux 2.6.27)
Number of bytes of RAM linearly mapped by kernel in
2 MB pages. (x86 with neither CONFIG_X86_64 nor
CONFIG_X86_PAE enabled.)
DirectMap1G %lu (since Linux 2.6.27)
(x86 with CONFIG_X86_64 and
CONFIG_X86_DIRECT_GBPAGES enabled.)
/proc/modules
A text list of the modules that have been loaded by the
system. See also lsmod(8).
/proc/mounts
Before kernel 2.4.19, this file was a list of all the
filesystems currently mounted on the system. With the
introduction of per-process mount namespaces in Linux
2.4.19 (see mount_namespaces(7)), this file became a link
to /proc/self/mounts, which lists the mounts of the
process's own mount namespace. The format of this file is
documented in fstab(5).
/proc/mtrr
Memory Type Range Registers. See the Linux kernel source
file Documentation/x86/mtrr.txt (or Documentation/mtrr.txt
before Linux 2.6.28) for details.
/proc/net
This directory contains various files and subdirectories
containing information about the networking layer. The
files contain ASCII structures and are, therefore,
readable with cat(1). However, the standard netstat(8)
suite provides much cleaner access to these files.
With the advent of network namespaces, various information
relating to the network stack is virtualized (see
network_namespaces(7)). Thus, since Linux 2.6.25,
/proc/net is a symbolic link to the directory
/proc/self/net, which contains the same files and
directories as listed below. However, these files and
directories now expose information for the network
namespace of which the process is a member.
/proc/net/arp
This holds an ASCII readable dump of the kernel ARP table
used for address resolutions. It will show both
dynamically learned and preprogrammed ARP entries. The
format is:
IP address HW type Flags HW address Mask Device
192.168.0.50 0x1 0x2 00:50:BF:25:68:F3 * eth0
192.168.0.250 0x1 0xc 00:00:00:00:00:00 * eth0
Here "IP address" is the IPv4 address of the machine and
the "HW type" is the hardware type of the address from
RFC 826. The flags are the internal flags of the ARP
structure (as defined in /usr/include/linux/if_arp.h) and
the "HW address" is the data link layer mapping for that
IP address if it is known.
/proc/net/dev
The dev pseudo-file contains network device status
information. This gives the number of received and sent
packets, the number of errors and collisions and other
basic statistics. These are used by the ifconfig(8)
program to report device status. The format is:
Inter-| Receive | Transmit
face |bytes packets errs drop fifo frame compressed multicast|bytes packets errs drop fifo colls carrier compressed
lo: 2776770 11307 0 0 0 0 0 0 2776770 11307 0 0 0 0 0 0
eth0: 1215645 2751 0 0 0 0 0 0 1782404 4324 0 0 0 427 0 0
ppp0: 1622270 5552 1 0 0 0 0 0 354130 5669 0 0 0 0 0 0
tap0: 7714 81 0 0 0 0 0 0 7714 81 0 0 0 0 0 0
/proc/net/dev_mcast
Defined in /usr/src/linux/net/core/dev_mcast.c:
indx interface_name dmi_u dmi_g dmi_address
2 eth0 1 0 01005e000001
3 eth1 1 0 01005e000001
4 eth2 1 0 01005e000001
/proc/net/igmp
Internet Group Management Protocol. Defined in
/usr/src/linux/net/core/igmp.c.
/proc/net/rarp
This file uses the same format as the arp file and
contains the current reverse mapping database used to
provide rarp(8) reverse address lookup services. If RARP
is not configured into the kernel, this file will not be
present.
/proc/net/raw
Holds a dump of the RAW socket table. Much of the
information is not of use apart from debugging. The "sl"
value is the kernel hash slot for the socket, the
"local_address" is the local address and protocol number
pair. "St" is the internal status of the socket. The
"tx_queue" and "rx_queue" are the outgoing and incoming
data queue in terms of kernel memory usage. The "tr",
"tm->when", and "rexmits" fields are not used by RAW. The
"uid" field holds the effective UID of the creator of the
socket.
/proc/net/snmp
This file holds the ASCII data needed for the IP, ICMP,
TCP, and UDP management information bases for an SNMP
agent.
/proc/net/tcp
Holds a dump of the TCP socket table. Much of the
information is not of use apart from debugging. The "sl"
value is the kernel hash slot for the socket, the
"local_address" is the local address and port number pair.
The "rem_address" is the remote address and port number
pair (if connected). "St" is the internal status of the
socket. The "tx_queue" and "rx_queue" are the outgoing
and incoming data queue in terms of kernel memory usage.
The "tr", "tm->when", and "rexmits" fields hold internal
information of the kernel socket state and are useful only
for debugging. The "uid" field holds the effective UID of
the creator of the socket.
/proc/net/udp
Holds a dump of the UDP socket table. Much of the
information is not of use apart from debugging. The "sl"
value is the kernel hash slot for the socket, the
"local_address" is the local address and port number pair.
The "rem_address" is the remote address and port number
pair (if connected). "St" is the internal status of the
socket. The "tx_queue" and "rx_queue" are the outgoing
and incoming data queue in terms of kernel memory usage.
The "tr", "tm->when", and "rexmits" fields are not used by
UDP. The "uid" field holds the effective UID of the
creator of the socket. The format is:
sl local_address rem_address st tx_queue rx_queue tr rexmits tm->when uid
1: 01642C89:0201 0C642C89:03FF 01 00000000:00000001 01:000071BA 00000000 0
1: 00000000:0801 00000000:0000 0A 00000000:00000000 00:00000000 6F000100 0
1: 00000000:0201 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0
/proc/net/unix
Lists the UNIX domain sockets present within the system
and their status. The format is:
Num RefCount Protocol Flags Type St Inode Path
0: 00000002 00000000 00000000 0001 03 42
1: 00000001 00000000 00010000 0001 01 1948 /dev/printer
The fields are as follows:
Num: the kernel table slot number.
RefCount:
the number of users of the socket.
Protocol:
currently always 0.
Flags: the internal kernel flags holding the status of the
socket.
Type: the socket type. For SOCK_STREAM sockets, this is
0001; for SOCK_DGRAM sockets, it is 0002; and for
SOCK_SEQPACKET sockets, it is 0005.
St: the internal state of the socket.
Inode: the inode number of the socket.
Path: the bound pathname (if any) of the socket. Sockets
in the abstract namespace are included in the list,
and are shown with a Path that commences with the
character '@'.
/proc/net/netfilter/nfnetlink_queue
This file contains information about netfilter user-space
queueing, if used. Each line represents a queue. Queues
that have not been subscribed to by user space are not
shown.
1 4207 0 2 65535 0 0 0 1
(1) (2) (3)(4) (5) (6) (7) (8)
The fields in each line are:
(1) The ID of the queue. This matches what is specified
in the --queue-num or --queue-balance options to the
iptables(8) NFQUEUE target. See
iptables-extensions(8) for more information.
(2) The netlink port ID subscribed to the queue.
(3) The number of packets currently queued and waiting to
be processed by the application.
(4) The copy mode of the queue. It is either 1 (metadata
only) or 2 (also copy payload data to user space).
(5) Copy range; that is, how many bytes of packet payload
should be copied to user space at most.
(6) queue dropped. Number of packets that had to be
dropped by the kernel because too many packets are
already waiting for user space to send back the
mandatory accept/drop verdicts.
(7) queue user dropped. Number of packets that were
dropped within the netlink subsystem. Such drops
usually happen when the corresponding socket buffer
is full; that is, user space is not able to read
messages fast enough.
(8) sequence number. Every queued packet is associated
with a (32-bit) monotonically increasing sequence
number. This shows the ID of the most recent packet
queued.
The last number exists only for compatibility reasons and
is always 1.
/proc/partitions
Contains the major and minor numbers of each partition as
well as the number of 1024-byte blocks and the partition
name.
/proc/pci
This is a listing of all PCI devices found during kernel
initialization and their configuration.
This file has been deprecated in favor of a new /proc
interface for PCI (/proc/bus/pci). It became optional in
Linux 2.2 (available with CONFIG_PCI_OLD_PROC set at
kernel compilation). It became once more nonoptionally
enabled in Linux 2.4. Next, it was deprecated in Linux
2.6 (still available with CONFIG_PCI_LEGACY_PROC set), and
finally removed altogether since Linux 2.6.17.
/proc/profile (since Linux 2.4)
This file is present only if the kernel was booted with
the profile=1 command-line option. It exposes kernel
profiling information in a binary format for use by
readprofile(1). Writing (e.g., an empty string) to this
file resets the profiling counters; on some architectures,
writing a binary integer "profiling multiplier" of size
sizeof(int) sets the profiling interrupt frequency.
/proc/scsi
A directory with the scsi mid-level pseudo-file and
various SCSI low-level driver directories, which contain a
file for each SCSI host in this system, all of which give
the status of some part of the SCSI IO subsystem. These
files contain ASCII structures and are, therefore,
readable with cat(1).
You can also write to some of the files to reconfigure the
subsystem or switch certain features on or off.
/proc/scsi/scsi
This is a listing of all SCSI devices known to the kernel.
The listing is similar to the one seen during bootup.
scsi currently supports only the add-single-device command
which allows root to add a hotplugged device to the list
of known devices.
The command
echo 'scsi add-single-device 1 0 5 0' > /proc/scsi/scsi
will cause host scsi1 to scan on SCSI channel 0 for a
device on ID 5 LUN 0. If there is already a device known
on this address or the address is invalid, an error will
be returned.
/proc/scsi/[drivername]
[drivername] can currently be NCR53c7xx, aha152x, aha1542,
aha1740, aic7xxx, buslogic, eata_dma, eata_pio, fdomain,
in2000, pas16, qlogic, scsi_debug, seagate, t128, u15-24f,
ultrastore, or wd7000. These directories show up for all
drivers that registered at least one SCSI HBA. Every
directory contains one file per registered host. Every
host-file is named after the number the host was assigned
during initialization.
Reading these files will usually show driver and host
configuration, statistics, and so on.
Writing to these files allows different things on
different hosts. For example, with the latency and
nolatency commands, root can switch on and off command
latency measurement code in the eata_dma driver. With the
lockup and unlock commands, root can control bus lockups
simulated by the scsi_debug driver.
/proc/self
This directory refers to the process accessing the /proc
filesystem, and is identical to the /proc directory named
by the process ID of the same process.
/proc/slabinfo
Information about kernel caches. See slabinfo(5) for
details.
/proc/stat
kernel/system statistics. Varies with architecture.
Common entries include:
cpu 10132153 290696 3084719 46828483 16683 0 25195 0
175628 0
cpu0 1393280 32966 572056 13343292 6130 0 17875 0 23933 0
The amount of time, measured in units of USER_HZ
(1/100ths of a second on most architectures, use
sysconf(_SC_CLK_TCK) to obtain the right value),
that the system ("cpu" line) or the specific CPU
("cpuN" line) spent in various states:
user (1) Time spent in user mode.
nice (2) Time spent in user mode with low
priority (nice).
system (3) Time spent in system mode.
idle (4) Time spent in the idle task. This value
should be USER_HZ times the second entry in
the /proc/uptime pseudo-file.
iowait (since Linux 2.5.41)
(5) Time waiting for I/O to complete. This
value is not reliable, for the following
reasons:
1. The CPU will not wait for I/O to
complete; iowait is the time that a task
is waiting for I/O to complete. When a
CPU goes into idle state for outstanding
task I/O, another task will be scheduled
on this CPU.
2. On a multi-core CPU, the task waiting for
I/O to complete is not running on any
CPU, so the iowait of each CPU is
difficult to calculate.
3. The value in this field may decrease in
certain conditions.
irq (since Linux 2.6.0)
(6) Time servicing interrupts.
softirq (since Linux 2.6.0)
(7) Time servicing softirqs.
steal (since Linux 2.6.11)
(8) Stolen time, which is the time spent in
other operating systems when running in a
virtualized environment
guest (since Linux 2.6.24)
(9) Time spent running a virtual CPU for
guest operating systems under the control of
the Linux kernel.
guest_nice (since Linux 2.6.33)
(10) Time spent running a niced guest
(virtual CPU for guest operating systems
under the control of the Linux kernel).
page 5741 1808
The number of pages the system paged in and the
number that were paged out (from disk).
swap 1 0
The number of swap pages that have been brought in
and out.
intr 1462898
This line shows counts of interrupts serviced since
boot time, for each of the possible system
interrupts. The first column is the total of all
interrupts serviced including unnumbered
architecture specific interrupts; each subsequent
column is the total for that particular numbered
interrupt. Unnumbered interrupts are not shown,
only summed into the total.
disk_io: (2,0):(31,30,5764,1,2) (3,0):...
(major,disk_idx):(noinfo, read_io_ops, blks_read,
write_io_ops, blks_written)
(Linux 2.4 only)
ctxt 115315
The number of context switches that the system
underwent.
btime 769041601
boot time, in seconds since the Epoch, 1970-01-01
00:00:00 +0000 (UTC).
processes 86031
Number of forks since boot.
procs_running 6
Number of processes in runnable state. (Linux
2.5.45 onward.)
procs_blocked 2
Number of processes blocked waiting for I/O to
complete. (Linux 2.5.45 onward.)
softirq 229245889 94 60001584 13619 5175704 2471304 28
51212741 59130143 0 51240672
This line shows the number of softirq for all CPUs.
The first column is the total of all softirqs and
each subsequent column is the total for particular
softirq. (Linux 2.6.31 onward.)
/proc/swaps
Swap areas in use. See also swapon(8).
/proc/sys
This directory (present since 1.3.57) contains a number of
files and subdirectories corresponding to kernel
variables. These variables can be read and in some cases
modified using the /proc filesystem, and the (deprecated)
sysctl(2) system call.
String values may be terminated by either '\0' or '\n'.
Integer and long values may be written either in decimal
or in hexadecimal notation (e.g., 0x3FFF). When writing
multiple integer or long values, these may be separated by
any of the following whitespace characters: ' ', '\t', or
'\n'. Using other separators leads to the error EINVAL.
/proc/sys/abi (since Linux 2.4.10)
This directory may contain files with application binary
information. See the Linux kernel source file
Documentation/sysctl/abi.txt for more information.
/proc/sys/debug
This directory may be empty.
/proc/sys/dev
This directory contains device-specific information (e.g.,
dev/cdrom/info). On some systems, it may be empty.
/proc/sys/fs
This directory contains the files and subdirectories for
kernel variables related to filesystems.
/proc/sys/fs/aio-max-nr and /proc/sys/fs/aio-nr (since Linux
2.6.4)
aio-nr is the running total of the number of events
specified by io_setup(2) calls for all currently active
AIO contexts. If aio-nr reaches aio-max-nr, then
io_setup(2) will fail with the error EAGAIN. Raising
aio-max-nr does not result in the preallocation or
resizing of any kernel data structures.
/proc/sys/fs/binfmt_misc
Documentation for files in this directory can be found in
the Linux kernel source in the file
Documentation/admin-guide/binfmt-misc.rst (or in
Documentation/binfmt_misc.txt on older kernels).
/proc/sys/fs/dentry-state (since Linux 2.2)
This file contains information about the status of the
directory cache (dcache). The file contains six numbers,
nr_dentry, nr_unused, age_limit (age in seconds),
want_pages (pages requested by system) and two dummy
values.
* nr_dentry is the number of allocated dentries (dcache
entries). This field is unused in Linux 2.2.
* nr_unused is the number of unused dentries.
* age_limit is the age in seconds after which dcache
entries can be reclaimed when memory is short.
* want_pages is nonzero when the kernel has called
shrink_dcache_pages() and the dcache isn't pruned yet.
/proc/sys/fs/dir-notify-enable
This file can be used to disable or enable the dnotify
interface described in fcntl(2) on a system-wide basis. A
value of 0 in this file disables the interface, and a
value of 1 enables it.
/proc/sys/fs/dquot-max
This file shows the maximum number of cached disk quota
entries. On some (2.4) systems, it is not present. If
the number of free cached disk quota entries is very low
and you have some awesome number of simultaneous system
users, you might want to raise the limit.
/proc/sys/fs/dquot-nr
This file shows the number of allocated disk quota entries
and the number of free disk quota entries.
/proc/sys/fs/epoll (since Linux 2.6.28)
This directory contains the file max_user_watches, which
can be used to limit the amount of kernel memory consumed
by the epoll interface. For further details, see
epoll(7).
/proc/sys/fs/file-max
This file defines a system-wide limit on the number of
open files for all processes. System calls that fail when
encountering this limit fail with the error ENFILE. (See
also setrlimit(2), which can be used by a process to set
the per-process limit, RLIMIT_NOFILE, on the number of
files it may open.) If you get lots of error messages in
the kernel log about running out of file handles (open
file descriptions) (look for "VFS: file-max limit <number>
reached"), try increasing this value:
echo 100000 > /proc/sys/fs/file-max
Privileged processes (CAP_SYS_ADMIN) can override the
file-max limit.
/proc/sys/fs/file-nr
This (read-only) file contains three numbers: the number
of allocated file handles (i.e., the number of open file
descriptions; see open(2)); the number of free file
handles; and the maximum number of file handles (i.e., the
same value as /proc/sys/fs/file-max). If the number of
allocated file handles is close to the maximum, you should
consider increasing the maximum. Before Linux 2.6, the
kernel allocated file handles dynamically, but it didn't
free them again. Instead the free file handles were kept
in a list for reallocation; the "free file handles" value
indicates the size of that list. A large number of free
file handles indicates that there was a past peak in the
usage of open file handles. Since Linux 2.6, the kernel
does deallocate freed file handles, and the "free file
handles" value is always zero.
/proc/sys/fs/inode-max (only present until Linux 2.2)
This file contains the maximum number of in-memory inodes.
This value should be 3–4 times larger than the value in
file-max, since stdin, stdout and network sockets also
need an inode to handle them. When you regularly run out
of inodes, you need to increase this value.
Starting with Linux 2.4, there is no longer a static limit
on the number of inodes, and this file is removed.
/proc/sys/fs/inode-nr
This file contains the first two values from inode-state.
/proc/sys/fs/inode-state
This file contains seven numbers: nr_inodes,
nr_free_inodes, preshrink, and four dummy values (always
zero).
nr_inodes is the number of inodes the system has
allocated. nr_free_inodes represents the number of free
inodes.
preshrink is nonzero when the nr_inodes > inode-max and
the system needs to prune the inode list instead of
allocating more; since Linux 2.4, this field is a dummy
value (always zero).
/proc/sys/fs/inotify (since Linux 2.6.13)
This directory contains files max_queued_events,
max_user_instances, and max_user_watches, that can be used
to limit the amount of kernel memory consumed by the
inotify interface. For further details, see inotify(7).
/proc/sys/fs/lease-break-time
This file specifies the grace period that the kernel
grants to a process holding a file lease (fcntl(2)) after
it has sent a signal to that process notifying it that
another process is waiting to open the file. If the lease
holder does not remove or downgrade the lease within this
grace period, the kernel forcibly breaks the lease.
/proc/sys/fs/leases-enable
This file can be used to enable or disable file leases
(fcntl(2)) on a system-wide basis. If this file contains
the value 0, leases are disabled. A nonzero value enables
leases.
/proc/sys/fs/mount-max (since Linux 4.9)
The value in this file specifies the maximum number of
mounts that may exist in a mount namespace. The default
value in this file is 100,000.
/proc/sys/fs/mqueue (since Linux 2.6.6)
This directory contains files msg_max, msgsize_max, and
queues_max, controlling the resources used by POSIX
message queues. See mq_overview(7) for details.
/proc/sys/fs/nr_open (since Linux 2.6.25)
This file imposes a ceiling on the value to which the
RLIMIT_NOFILE resource limit can be raised (see
getrlimit(2)). This ceiling is enforced for both
unprivileged and privileged process. The default value in
this file is 1048576. (Before Linux 2.6.25, the ceiling
for RLIMIT_NOFILE was hard-coded to the same value.)
/proc/sys/fs/overflowgid and /proc/sys/fs/overflowuid
These files allow you to change the value of the fixed UID
and GID. The default is 65534. Some filesystems support
only 16-bit UIDs and GIDs, although in Linux UIDs and GIDs
are 32 bits. When one of these filesystems is mounted
with writes enabled, any UID or GID that would exceed
65535 is translated to the overflow value before being
written to disk.
/proc/sys/fs/pipe-max-size (since Linux 2.6.35)
See pipe(7).
/proc/sys/fs/pipe-user-pages-hard (since Linux 4.5)
See pipe(7).
/proc/sys/fs/pipe-user-pages-soft (since Linux 4.5)
See pipe(7).
/proc/sys/fs/protected_fifos (since Linux 4.19)
The value in this file is/can be set to one of the
following:
0 Writing to FIFOs is unrestricted.
1 Don't allow O_CREAT open(2) on FIFOs that the caller
doesn't own in world-writable sticky directories,
unless the FIFO is owned by the owner of the
directory.
2 As for the value 1, but the restriction also applies
to group-writable sticky directories.
The intent of the above protections is to avoid
unintentional writes to an attacker-controlled FIFO when a
program expected to create a regular file.
/proc/sys/fs/protected_hardlinks (since Linux 3.6)
When the value in this file is 0, no restrictions are
placed on the creation of hard links (i.e., this is the
historical behavior before Linux 3.6). When the value in
this file is 1, a hard link can be created to a target
file only if one of the following conditions is true:
* The calling process has the CAP_FOWNER capability in
its user namespace and the file UID has a mapping in
the namespace.
* The filesystem UID of the process creating the link
matches the owner (UID) of the target file (as
described in credentials(7), a process's filesystem UID
is normally the same as its effective UID).
* All of the following conditions are true:
• the target is a regular file;
• the target file does not have its set-user-ID mode
bit enabled;
• the target file does not have both its set-group-ID
and group-executable mode bits enabled; and
• the caller has permission to read and write the
target file (either via the file's permissions mask
or because it has suitable capabilities).
The default value in this file is 0. Setting the value to
1 prevents a longstanding class of security issues caused
by hard-link-based time-of-check, time-of-use races, most
commonly seen in world-writable directories such as /tmp.
The common method of exploiting this flaw is to cross
privilege boundaries when following a given hard link
(i.e., a root process follows a hard link created by
another user). Additionally, on systems without separated
partitions, this stops unauthorized users from "pinning"
vulnerable set-user-ID and set-group-ID files against
being upgraded by the administrator, or linking to special
files.
/proc/sys/fs/protected_regular (since Linux 4.19)
The value in this file is/can be set to one of the
following:
0 Writing to regular files is unrestricted.
1 Don't allow O_CREAT open(2) on regular files that the
caller doesn't own in world-writable sticky
directories, unless the regular file is owned by the
owner of the directory.
2 As for the value 1, but the restriction also applies
to group-writable sticky directories.
The intent of the above protections is similar to
protected_fifos, but allows an application to avoid writes
to an attacker-controlled regular file, where the
application expected to create one.
/proc/sys/fs/protected_symlinks (since Linux 3.6)
When the value in this file is 0, no restrictions are
placed on following symbolic links (i.e., this is the
historical behavior before Linux 3.6). When the value in
this file is 1, symbolic links are followed only in the
following circumstances:
* the filesystem UID of the process following the link
matches the owner (UID) of the symbolic link (as
described in credentials(7), a process's filesystem UID
is normally the same as its effective UID);
* the link is not in a sticky world-writable directory;
or
* the symbolic link and its parent directory have the
same owner (UID)
A system call that fails to follow a symbolic link because
of the above restrictions returns the error EACCES in
errno.
The default value in this file is 0. Setting the value to
1 avoids a longstanding class of security issues based on
time-of-check, time-of-use races when accessing symbolic
links.
/proc/sys/fs/suid_dumpable (since Linux 2.6.13)
The value in this file is assigned to a process's
"dumpable" flag in the circumstances described in
prctl(2). In effect, the value in this file determines
whether core dump files are produced for set-user-ID or
otherwise protected/tainted binaries. The "dumpable"
setting also affects the ownership of files in a process's
/proc/[pid] directory, as described above.
Three different integer values can be specified:
0 (default)
This provides the traditional (pre-Linux 2.6.13)
behavior. A core dump will not be produced for a
process which has changed credentials (by calling
seteuid(2), setgid(2), or similar, or by executing
a set-user-ID or set-group-ID program) or whose
binary does not have read permission enabled.
1 ("debug")
All processes dump core when possible. (Reasons
why a process might nevertheless not dump core are
described in core(5).) The core dump is owned by
the filesystem user ID of the dumping process and
no security is applied. This is intended for
system debugging situations only: this mode is
insecure because it allows unprivileged users to
examine the memory contents of privileged
processes.
2 ("suidsafe")
Any binary which normally would not be dumped (see
"0" above) is dumped readable by root only. This
allows the user to remove the core dump file but
not to read it. For security reasons core dumps in
this mode will not overwrite one another or other
files. This mode is appropriate when
administrators are attempting to debug problems in
a normal environment.
Additionally, since Linux 3.6,
/proc/sys/kernel/core_pattern must either be an
absolute pathname or a pipe command, as detailed in
core(5). Warnings will be written to the kernel
log if core_pattern does not follow these rules,
and no core dump will be produced.
For details of the effect of a process's "dumpable"
setting on ptrace access mode checking, see ptrace(2).
/proc/sys/fs/super-max
This file controls the maximum number of superblocks, and
thus the maximum number of mounted filesystems the kernel
can have. You need increase only super-max if you need to
mount more filesystems than the current value in super-max
allows you to.
/proc/sys/fs/super-nr
This file contains the number of filesystems currently
mounted.
/proc/sys/kernel
This directory contains files controlling a range of
kernel parameters, as described below.
/proc/sys/kernel/acct
This file contains three numbers: highwater, lowwater, and
frequency. If BSD-style process accounting is enabled,
these values control its behavior. If free space on
filesystem where the log lives goes below lowwater
percent, accounting suspends. If free space gets above
highwater percent, accounting resumes. frequency
determines how often the kernel checks the amount of free
space (value is in seconds). Default values are 4, 2, and
30. That is, suspend accounting if 2% or less space is
free; resume it if 4% or more space is free; consider
information about amount of free space valid for 30
seconds.
/proc/sys/kernel/auto_msgmni (Linux 2.6.27 to 3.18)
From Linux 2.6.27 to 3.18, this file was used to control
recomputing of the value in /proc/sys/kernel/msgmni upon
the addition or removal of memory or upon IPC namespace
creation/removal. Echoing "1" into this file enabled
msgmni automatic recomputing (and triggered a
recomputation of msgmni based on the current amount of
available memory and number of IPC namespaces). Echoing
"0" disabled automatic recomputing. (Automatic
recomputing was also disabled if a value was explicitly
assigned to /proc/sys/kernel/msgmni.) The default value
in auto_msgmni was 1.
Since Linux 3.19, the content of this file has no effect
(because msgmni defaults to near the maximum value
possible), and reads from this file always return the
value "0".
/proc/sys/kernel/cap_last_cap (since Linux 3.2)
See capabilities(7).
/proc/sys/kernel/cap-bound (from Linux 2.2 to 2.6.24)
This file holds the value of the kernel capability
bounding set (expressed as a signed decimal number). This
set is ANDed against the capabilities permitted to a
process during execve(2). Starting with Linux 2.6.25, the
system-wide capability bounding set disappeared, and was
replaced by a per-thread bounding set; see
capabilities(7).
/proc/sys/kernel/core_pattern
See core(5).
/proc/sys/kernel/core_pipe_limit
See core(5).
/proc/sys/kernel/core_uses_pid
See core(5).
/proc/sys/kernel/ctrl-alt-del
This file controls the handling of Ctrl-Alt-Del from the
keyboard. When the value in this file is 0, Ctrl-Alt-Del
is trapped and sent to the init(1) program to handle a
graceful restart. When the value is greater than zero,
Linux's reaction to a Vulcan Nerve Pinch (tm) will be an
immediate reboot, without even syncing its dirty buffers.
Note: when a program (like dosemu) has the keyboard in
"raw" mode, the ctrl-alt-del is intercepted by the program
before it ever reaches the kernel tty layer, and it's up
to the program to decide what to do with it.
/proc/sys/kernel/dmesg_restrict (since Linux 2.6.37)
The value in this file determines who can see kernel
syslog contents. A value of 0 in this file imposes no
restrictions. If the value is 1, only privileged users
can read the kernel syslog. (See syslog(2) for more
details.) Since Linux 3.4, only users with the
CAP_SYS_ADMIN capability may change the value in this
file.
/proc/sys/kernel/domainname and /proc/sys/kernel/hostname
can be used to set the NIS/YP domainname and the hostname
of your box in exactly the same way as the commands
domainname(1) and hostname(1), that is:
# echo 'darkstar' > /proc/sys/kernel/hostname
# echo 'mydomain' > /proc/sys/kernel/domainname
has the same effect as
# hostname 'darkstar'
# domainname 'mydomain'
Note, however, that the classic darkstar.frop.org has the
hostname "darkstar" and DNS (Internet Domain Name Server)
domainname "frop.org", not to be confused with the NIS
(Network Information Service) or YP (Yellow Pages)
domainname. These two domain names are in general
different. For a detailed discussion see the hostname(1)
man page.
/proc/sys/kernel/hotplug
This file contains the pathname for the hotplug policy
agent. The default value in this file is /sbin/hotplug.
/proc/sys/kernel/htab-reclaim (before Linux 2.4.9.2)
(PowerPC only) If this file is set to a nonzero value, the
PowerPC htab (see kernel file
Documentation/powerpc/ppc_htab.txt) is pruned each time
the system hits the idle loop.
/proc/sys/kernel/keys/*
This directory contains various files that define
parameters and limits for the key-management facility.
These files are described in keyrings(7).
/proc/sys/kernel/kptr_restrict (since Linux 2.6.38)
The value in this file determines whether kernel addresses
are exposed via /proc files and other interfaces. A value
of 0 in this file imposes no restrictions. If the value
is 1, kernel pointers printed using the %pK format
specifier will be replaced with zeros unless the user has
the CAP_SYSLOG capability. If the value is 2, kernel
pointers printed using the %pK format specifier will be
replaced with zeros regardless of the user's capabilities.
The initial default value for this file was 1, but the
default was changed to 0 in Linux 2.6.39. Since Linux
3.4, only users with the CAP_SYS_ADMIN capability can
change the value in this file.
/proc/sys/kernel/l2cr
(PowerPC only) This file contains a flag that controls the
L2 cache of G3 processor boards. If 0, the cache is
disabled. Enabled if nonzero.
/proc/sys/kernel/modprobe
This file contains the pathname for the kernel module
loader. The default value is /sbin/modprobe. The file is
present only if the kernel is built with the
CONFIG_MODULES (CONFIG_KMOD in Linux 2.6.26 and earlier)
option enabled. It is described by the Linux kernel
source file Documentation/kmod.txt (present only in kernel
2.4 and earlier).
/proc/sys/kernel/modules_disabled (since Linux 2.6.31)
A toggle value indicating if modules are allowed to be
loaded in an otherwise modular kernel. This toggle
defaults to off (0), but can be set true (1). Once true,
modules can be neither loaded nor unloaded, and the toggle
cannot be set back to false. The file is present only if
the kernel is built with the CONFIG_MODULES option
enabled.
/proc/sys/kernel/msgmax (since Linux 2.2)
This file defines a system-wide limit specifying the
maximum number of bytes in a single message written on a
System V message queue.
/proc/sys/kernel/msgmni (since Linux 2.4)
This file defines the system-wide limit on the number of
message queue identifiers. See also
/proc/sys/kernel/auto_msgmni.
/proc/sys/kernel/msgmnb (since Linux 2.2)
This file defines a system-wide parameter used to
initialize the msg_qbytes setting for subsequently created
message queues. The msg_qbytes setting specifies the
maximum number of bytes that may be written to the message
queue.
/proc/sys/kernel/ngroups_max (since Linux 2.6.4)
This is a read-only file that displays the upper limit on
the number of a process's group memberships.
/proc/sys/kernel/ns_last_pid (since Linux 3.3)
See pid_namespaces(7).
/proc/sys/kernel/ostype and /proc/sys/kernel/osrelease
These files give substrings of /proc/version.
/proc/sys/kernel/overflowgid and /proc/sys/kernel/overflowuid
These files duplicate the files /proc/sys/fs/overflowgid
and /proc/sys/fs/overflowuid.
/proc/sys/kernel/panic
This file gives read/write access to the kernel variable
panic_timeout. If this is zero, the kernel will loop on a
panic; if nonzero, it indicates that the kernel should
autoreboot after this number of seconds. When you use the
software watchdog device driver, the recommended setting
is 60.
/proc/sys/kernel/panic_on_oops (since Linux 2.5.68)
This file controls the kernel's behavior when an oops or
BUG is encountered. If this file contains 0, then the
system tries to continue operation. If it contains 1,
then the system delays a few seconds (to give klogd time
to record the oops output) and then panics. If the
/proc/sys/kernel/panic file is also nonzero, then the
machine will be rebooted.
/proc/sys/kernel/pid_max (since Linux 2.5.34)
This file specifies the value at which PIDs wrap around
(i.e., the value in this file is one greater than the
maximum PID). PIDs greater than this value are not
allocated; thus, the value in this file also acts as a
system-wide limit on the total number of processes and
threads. The default value for this file, 32768, results
in the same range of PIDs as on earlier kernels. On
32-bit platforms, 32768 is the maximum value for pid_max.
On 64-bit systems, pid_max can be set to any value up to
2^22 (PID_MAX_LIMIT, approximately 4 million).
/proc/sys/kernel/powersave-nap (PowerPC only)
This file contains a flag. If set, Linux-PPC will use the
"nap" mode of powersaving, otherwise the "doze" mode will
be used.
/proc/sys/kernel/printk
See syslog(2).
/proc/sys/kernel/pty (since Linux 2.6.4)
This directory contains two files relating to the number
of UNIX 98 pseudoterminals (see pts(4)) on the system.
/proc/sys/kernel/pty/max
This file defines the maximum number of pseudoterminals.
/proc/sys/kernel/pty/nr
This read-only file indicates how many pseudoterminals are
currently in use.
/proc/sys/kernel/random
This directory contains various parameters controlling the
operation of the file /dev/random. See random(4) for
further information.
/proc/sys/kernel/random/uuid (since Linux 2.4)
Each read from this read-only file returns a randomly
generated 128-bit UUID, as a string in the standard UUID
format.
/proc/sys/kernel/randomize_va_space (since Linux 2.6.12)
Select the address space layout randomization (ASLR)
policy for the system (on architectures that support
ASLR). Three values are supported for this file:
0 Turn ASLR off. This is the default for architectures
that don't support ASLR, and when the kernel is booted
with the norandmaps parameter.
1 Make the addresses of mmap(2) allocations, the stack,
and the VDSO page randomized. Among other things, this
means that shared libraries will be loaded at
randomized addresses. The text segment of PIE-linked
binaries will also be loaded at a randomized address.
This value is the default if the kernel was configured
with CONFIG_COMPAT_BRK.
2 (Since Linux 2.6.25) Also support heap randomization.
This value is the default if the kernel was not
configured with CONFIG_COMPAT_BRK.
/proc/sys/kernel/real-root-dev
This file is documented in the Linux kernel source file
Documentation/admin-guide/initrd.rst (or
Documentation/initrd.txt before Linux 4.10).
/proc/sys/kernel/reboot-cmd (Sparc only)
This file seems to be a way to give an argument to the
SPARC ROM/Flash boot loader. Maybe to tell it what to do
after rebooting?
/proc/sys/kernel/rtsig-max
(Only in kernels up to and including 2.6.7; see
setrlimit(2)) This file can be used to tune the maximum
number of POSIX real-time (queued) signals that can be
outstanding in the system.
/proc/sys/kernel/rtsig-nr
(Only in kernels up to and including 2.6.7.) This file
shows the number of POSIX real-time signals currently
queued.
/proc/[pid]/sched_autogroup_enabled (since Linux 2.6.38)
See sched(7).
/proc/sys/kernel/sched_child_runs_first (since Linux 2.6.23)
If this file contains the value zero, then, after a
fork(2), the parent is first scheduled on the CPU. If the
file contains a nonzero value, then the child is scheduled
first on the CPU. (Of course, on a multiprocessor system,
the parent and the child might both immediately be
scheduled on a CPU.)
/proc/sys/kernel/sched_rr_timeslice_ms (since Linux 3.9)
See sched_rr_get_interval(2).
/proc/sys/kernel/sched_rt_period_us (since Linux 2.6.25)
See sched(7).
/proc/sys/kernel/sched_rt_runtime_us (since Linux 2.6.25)
See sched(7).
/proc/sys/kernel/seccomp (since Linux 4.14)
This directory provides additional seccomp information and
configuration. See seccomp(2) for further details.
/proc/sys/kernel/sem (since Linux 2.4)
This file contains 4 numbers defining limits for System V
IPC semaphores. These fields are, in order:
SEMMSL The maximum semaphores per semaphore set.
SEMMNS A system-wide limit on the number of semaphores in
all semaphore sets.
SEMOPM The maximum number of operations that may be
specified in a semop(2) call.
SEMMNI A system-wide limit on the maximum number of
semaphore identifiers.
/proc/sys/kernel/sg-big-buff
This file shows the size of the generic SCSI device (sg)
buffer. You can't tune it just yet, but you could change
it at compile time by editing include/scsi/sg.h and
changing the value of SG_BIG_BUFF. However, there
shouldn't be any reason to change this value.
/proc/sys/kernel/shm_rmid_forced (since Linux 3.1)
If this file is set to 1, all System V shared memory
segments will be marked for destruction as soon as the
number of attached processes falls to zero; in other
words, it is no longer possible to create shared memory
segments that exist independently of any attached process.
The effect is as though a shmctl(2) IPC_RMID is performed
on all existing segments as well as all segments created
in the future (until this file is reset to 0). Note that
existing segments that are attached to no process will be
immediately destroyed when this file is set to 1. Setting
this option will also destroy segments that were created,
but never attached, upon termination of the process that
created the segment with shmget(2).
Setting this file to 1 provides a way of ensuring that all
System V shared memory segments are counted against the
resource usage and resource limits (see the description of
RLIMIT_AS in getrlimit(2)) of at least one process.
Because setting this file to 1 produces behavior that is
nonstandard and could also break existing applications,
the default value in this file is 0. Set this file to 1
only if you have a good understanding of the semantics of
the applications using System V shared memory on your
system.
/proc/sys/kernel/shmall (since Linux 2.2)
This file contains the system-wide limit on the total
number of pages of System V shared memory.
/proc/sys/kernel/shmmax (since Linux 2.2)
This file can be used to query and set the run-time limit
on the maximum (System V IPC) shared memory segment size
that can be created. Shared memory segments up to 1 GB
are now supported in the kernel. This value defaults to
SHMMAX.
/proc/sys/kernel/shmmni (since Linux 2.4)
This file specifies the system-wide maximum number of
System V shared memory segments that can be created.
/proc/sys/kernel/sysctl_writes_strict (since Linux 3.16)
The value in this file determines how the file offset
affects the behavior of updating entries in files under
/proc/sys. The file has three possible values:
-1 This provides legacy handling, with no printk
warnings. Each write(2) must fully contain the value
to be written, and multiple writes on the same file
descriptor will overwrite the entire value, regardless
of the file position.
0 (default) This provides the same behavior as for -1,
but printk warnings are written for processes that
perform writes when the file offset is not 0.
1 Respect the file offset when writing strings into
/proc/sys files. Multiple writes will append to the
value buffer. Anything written beyond the maximum
length of the value buffer will be ignored. Writes to
numeric /proc/sys entries must always be at file
offset 0 and the value must be fully contained in the
buffer provided to write(2).
/proc/sys/kernel/sysrq
This file controls the functions allowed to be invoked by
the SysRq key. By default, the file contains 1 meaning
that every possible SysRq request is allowed (in older
kernel versions, SysRq was disabled by default, and you
were required to specifically enable it at run-time, but
this is not the case any more). Possible values in this
file are:
0 Disable sysrq completely
1 Enable all functions of sysrq
> 1 Bit mask of allowed sysrq functions, as follows:
2 Enable control of console logging level
4 Enable control of keyboard (SAK, unraw)
8 Enable debugging dumps of processes etc.
16 Enable sync command
32 Enable remount read-only
64 Enable signaling of processes (term, kill, oom-
kill)
128 Allow reboot/poweroff
256 Allow nicing of all real-time tasks
This file is present only if the CONFIG_MAGIC_SYSRQ kernel
configuration option is enabled. For further details see
the Linux kernel source file
Documentation/admin-guide/sysrq.rst (or
Documentation/sysrq.txt before Linux 4.10).
/proc/sys/kernel/version
This file contains a string such as:
#5 Wed Feb 25 21:49:24 MET 1998
The "#5" means that this is the fifth kernel built from
this source base and the date following it indicates the
time the kernel was built.
/proc/sys/kernel/threads-max (since Linux 2.3.11)
This file specifies the system-wide limit on the number of
threads (tasks) that can be created on the system.
Since Linux 4.1, the value that can be written to
threads-max is bounded. The minimum value that can be
written is 20. The maximum value that can be written is
given by the constant FUTEX_TID_MASK (0x3fffffff). If a
value outside of this range is written to threads-max, the
error EINVAL occurs.
The value written is checked against the available RAM
pages. If the thread structures would occupy too much
(more than 1/8th) of the available RAM pages, threads-max
is reduced accordingly.
/proc/sys/kernel/yama/ptrace_scope (since Linux 3.5)
See ptrace(2).
/proc/sys/kernel/zero-paged (PowerPC only)
This file contains a flag. When enabled (nonzero), Linux-
PPC will pre-zero pages in the idle loop, possibly
speeding up get_free_pages.
/proc/sys/net
This directory contains networking stuff. Explanations
for some of the files under this directory can be found in
tcp(7) and ip(7).
/proc/sys/net/core/bpf_jit_enable
See bpf(2).
/proc/sys/net/core/somaxconn
This file defines a ceiling value for the backlog argument
of listen(2); see the listen(2) manual page for details.
/proc/sys/proc
This directory may be empty.
/proc/sys/sunrpc
This directory supports Sun remote procedure call for
network filesystem (NFS). On some systems, it is not
present.
/proc/sys/user (since Linux 4.9)
See namespaces(7).
/proc/sys/vm
This directory contains files for memory management
tuning, buffer, and cache management.
/proc/sys/vm/admin_reserve_kbytes (since Linux 3.10)
This file defines the amount of free memory (in KiB) on
the system that should be reserved for users with the
capability CAP_SYS_ADMIN.
The default value in this file is the minimum of [3% of
free pages, 8MiB] expressed as KiB. The default is
intended to provide enough for the superuser to log in and
kill a process, if necessary, under the default overcommit
'guess' mode (i.e., 0 in /proc/sys/vm/overcommit_memory).
Systems running in "overcommit never" mode (i.e., 2 in
/proc/sys/vm/overcommit_memory) should increase the value
in this file to account for the full virtual memory size
of the programs used to recover (e.g., login(1) ssh(1),
and top(1)) Otherwise, the superuser may not be able to
log in to recover the system. For example, on x86-64 a
suitable value is 131072 (128MiB reserved).
Changing the value in this file takes effect whenever an
application requests memory.
/proc/sys/vm/compact_memory (since Linux 2.6.35)
When 1 is written to this file, all zones are compacted
such that free memory is available in contiguous blocks
where possible. The effect of this action can be seen by
examining /proc/buddyinfo.
Present only if the kernel was configured with
CONFIG_COMPACTION.
/proc/sys/vm/drop_caches (since Linux 2.6.16)
Writing to this file causes the kernel to drop clean
caches, dentries, and inodes from memory, causing that
memory to become free. This can be useful for memory
management testing and performing reproducible filesystem
benchmarks. Because writing to this file causes the
benefits of caching to be lost, it can degrade overall
system performance.
To free pagecache, use:
echo 1 > /proc/sys/vm/drop_caches
To free dentries and inodes, use:
echo 2 > /proc/sys/vm/drop_caches
To free pagecache, dentries, and inodes, use:
echo 3 > /proc/sys/vm/drop_caches
Because writing to this file is a nondestructive operation
and dirty objects are not freeable, the user should run
sync(1) first.
/proc/sys/vm/sysctl_hugetlb_shm_group (since Linux 2.6.7)
This writable file contains a group ID that is allowed to
allocate memory using huge pages. If a process has a
filesystem group ID or any supplementary group ID that
matches this group ID, then it can make huge-page
allocations without holding the CAP_IPC_LOCK capability;
see memfd_create(2), mmap(2), and shmget(2).
/proc/sys/vm/legacy_va_layout (since Linux 2.6.9)
If nonzero, this disables the new 32-bit memory-mapping
layout; the kernel will use the legacy (2.4) layout for
all processes.
/proc/sys/vm/memory_failure_early_kill (since Linux 2.6.32)
Control how to kill processes when an uncorrected memory
error (typically a 2-bit error in a memory module) that
cannot be handled by the kernel is detected in the
background by hardware. In some cases (like the page
still having a valid copy on disk), the kernel will handle
the failure transparently without affecting any
applications. But if there is no other up-to-date copy of
the data, it will kill processes to prevent any data
corruptions from propagating.
The file has one of the following values:
1: Kill all processes that have the corrupted-and-not-
reloadable page mapped as soon as the corruption is
detected. Note that this is not supported for a few
types of pages, such as kernel internally allocated
data or the swap cache, but works for the majority of
user pages.
0: Unmap the corrupted page from all processes and kill a
process only if it tries to access the page.
The kill is performed using a SIGBUS signal with si_code
set to BUS_MCEERR_AO. Processes can handle this if they
want to; see sigaction(2) for more details.
This feature is active only on architectures/platforms
with advanced machine check handling and depends on the
hardware capabilities.
Applications can override the memory_failure_early_kill
setting individually with the prctl(2) PR_MCE_KILL
operation.
Present only if the kernel was configured with
CONFIG_MEMORY_FAILURE.
/proc/sys/vm/memory_failure_recovery (since Linux 2.6.32)
Enable memory failure recovery (when supported by the
platform).
1: Attempt recovery.
0: Always panic on a memory failure.
Present only if the kernel was configured with
CONFIG_MEMORY_FAILURE.
/proc/sys/vm/oom_dump_tasks (since Linux 2.6.25)
Enables a system-wide task dump (excluding kernel threads)
to be produced when the kernel performs an OOM-killing.
The dump includes the following information for each task
(thread, process): thread ID, real user ID, thread group
ID (process ID), virtual memory size, resident set size,
the CPU that the task is scheduled on, oom_adj score (see
the description of /proc/[pid]/oom_adj), and command name.
This is helpful to determine why the OOM-killer was
invoked and to identify the rogue task that caused it.
If this contains the value zero, this information is
suppressed. On very large systems with thousands of
tasks, it may not be feasible to dump the memory state
information for each one. Such systems should not be
forced to incur a performance penalty in OOM situations
when the information may not be desired.
If this is set to nonzero, this information is shown
whenever the OOM-killer actually kills a memory-hogging
task.
The default value is 0.
/proc/sys/vm/oom_kill_allocating_task (since Linux 2.6.24)
This enables or disables killing the OOM-triggering task
in out-of-memory situations.
If this is set to zero, the OOM-killer will scan through
the entire tasklist and select a task based on heuristics
to kill. This normally selects a rogue memory-hogging
task that frees up a large amount of memory when killed.
If this is set to nonzero, the OOM-killer simply kills the
task that triggered the out-of-memory condition. This
avoids a possibly expensive tasklist scan.
If /proc/sys/vm/panic_on_oom is nonzero, it takes
precedence over whatever value is used in
/proc/sys/vm/oom_kill_allocating_task.
The default value is 0.
/proc/sys/vm/overcommit_kbytes (since Linux 3.14)
This writable file provides an alternative to
/proc/sys/vm/overcommit_ratio for controlling the
CommitLimit when /proc/sys/vm/overcommit_memory has the
value 2. It allows the amount of memory overcommitting to
be specified as an absolute value (in kB), rather than as
a percentage, as is done with overcommit_ratio. This
allows for finer-grained control of CommitLimit on systems
with extremely large memory sizes.
Only one of overcommit_kbytes or overcommit_ratio can have
an effect: if overcommit_kbytes has a nonzero value, then
it is used to calculate CommitLimit, otherwise
overcommit_ratio is used. Writing a value to either of
these files causes the value in the other file to be set
to zero.
/proc/sys/vm/overcommit_memory
This file contains the kernel virtual memory accounting
mode. Values are:
0: heuristic overcommit (this is the default)
1: always overcommit, never check
2: always check, never overcommit
In mode 0, calls of mmap(2) with MAP_NORESERVE are not
checked, and the default check is very weak, leading to
the risk of getting a process "OOM-killed".
In mode 1, the kernel pretends there is always enough
memory, until memory actually runs out. One use case for
this mode is scientific computing applications that employ
large sparse arrays. In Linux kernel versions before
2.6.0, any nonzero value implies mode 1.
In mode 2 (available since Linux 2.6), the total virtual
address space that can be allocated (CommitLimit in
/proc/meminfo) is calculated as
CommitLimit = (total_RAM - total_huge_TLB) *
overcommit_ratio / 100 + total_swap
where:
* total_RAM is the total amount of RAM on the
system;
* total_huge_TLB is the amount of memory set aside
for huge pages;
* overcommit_ratio is the value in
/proc/sys/vm/overcommit_ratio; and
* total_swap is the amount of swap space.
For example, on a system with 16 GB of physical RAM, 16 GB
of swap, no space dedicated to huge pages, and an
overcommit_ratio of 50, this formula yields a CommitLimit
of 24 GB.
Since Linux 3.14, if the value in
/proc/sys/vm/overcommit_kbytes is nonzero, then
CommitLimit is instead calculated as:
CommitLimit = overcommit_kbytes + total_swap
See also the description of
/proc/sys/vm/admin_reserve_kbytes and
/proc/sys/vm/user_reserve_kbytes.
/proc/sys/vm/overcommit_ratio (since Linux 2.6.0)
This writable file defines a percentage by which memory
can be overcommitted. The default value in the file is
50. See the description of
/proc/sys/vm/overcommit_memory.
/proc/sys/vm/panic_on_oom (since Linux 2.6.18)
This enables or disables a kernel panic in an out-of-
memory situation.
If this file is set to the value 0, the kernel's OOM-
killer will kill some rogue process. Usually, the OOM-
killer is able to kill a rogue process and the system will
survive.
If this file is set to the value 1, then the kernel
normally panics when out-of-memory happens. However, if a
process limits allocations to certain nodes using memory
policies (mbind(2) MPOL_BIND) or cpusets (cpuset(7)) and
those nodes reach memory exhaustion status, one process
may be killed by the OOM-killer. No panic occurs in this
case: because other nodes' memory may be free, this means
the system as a whole may not have reached an out-of-
memory situation yet.
If this file is set to the value 2, the kernel always
panics when an out-of-memory condition occurs.
The default value is 0. 1 and 2 are for failover of
clustering. Select either according to your policy of
failover.
/proc/sys/vm/swappiness
The value in this file controls how aggressively the
kernel will swap memory pages. Higher values increase
aggressiveness, lower values decrease aggressiveness. The
default value is 60.
/proc/sys/vm/user_reserve_kbytes (since Linux 3.10)
Specifies an amount of memory (in KiB) to reserve for user
processes. This is intended to prevent a user from
starting a single memory hogging process, such that they
cannot recover (kill the hog). The value in this file has
an effect only when /proc/sys/vm/overcommit_memory is set
to 2 ("overcommit never" mode). In this case, the system
reserves an amount of memory that is the minimum of [3% of
current process size, user_reserve_kbytes].
The default value in this file is the minimum of [3% of
free pages, 128MiB] expressed as KiB.
If the value in this file is set to zero, then a user will
be allowed to allocate all free memory with a single
process (minus the amount reserved by
/proc/sys/vm/admin_reserve_kbytes). Any subsequent
attempts to execute a command will result in "fork: Cannot
allocate memory".
Changing the value in this file takes effect whenever an
application requests memory.
/proc/sys/vm/unprivileged_userfaultfd (since Linux 5.2)
This (writable) file exposes a flag that controls whether
unprivileged processes are allowed to employ
userfaultfd(2). If this file has the value 1, then
unprivileged processes may use userfaultfd(2). If this
file has the value 0, then only processes that have the
CAP_SYS_PTRACE capability may employ userfaultfd(2). The
default value in this file is 1.
/proc/sysrq-trigger (since Linux 2.4.21)
Writing a character to this file triggers the same SysRq
function as typing ALT-SysRq-<character> (see the
description of /proc/sys/kernel/sysrq). This file is
normally writable only by root. For further details see
the Linux kernel source file
Documentation/admin-guide/sysrq.rst (or
Documentation/sysrq.txt before Linux 4.10).
/proc/sysvipc
Subdirectory containing the pseudo-files msg, sem and shm.
These files list the System V Interprocess Communication
(IPC) objects (respectively: message queues, semaphores,
and shared memory) that currently exist on the system,
providing similar information to that available via
ipcs(1). These files have headers and are formatted (one
IPC object per line) for easy understanding. sysvipc(7)
provides further background on the information shown by
these files.
/proc/thread-self (since Linux 3.17)
This directory refers to the thread accessing the /proc
filesystem, and is identical to the /proc/self/task/[tid]
directory named by the process thread ID ([tid]) of the
same thread.
/proc/timer_list (since Linux 2.6.21)
This read-only file exposes a list of all currently
pending (high-resolution) timers, all clock-event sources,
and their parameters in a human-readable form.
/proc/timer_stats (from Linux 2.6.21 until Linux 4.10)
This is a debugging facility to make timer (ab)use in a
Linux system visible to kernel and user-space developers.
It can be used by kernel and user-space developers to
verify that their code does not make undue use of timers.
The goal is to avoid unnecessary wakeups, thereby
optimizing power consumption.
If enabled in the kernel (CONFIG_TIMER_STATS), but not
used, it has almost zero run-time overhead and a
relatively small data-structure overhead. Even if
collection is enabled at run time, overhead is low: all
the locking is per-CPU and lookup is hashed.
The /proc/timer_stats file is used both to control
sampling facility and to read out the sampled information.
The timer_stats functionality is inactive on bootup. A
sampling period can be started using the following
command:
# echo 1 > /proc/timer_stats
The following command stops a sampling period:
# echo 0 > /proc/timer_stats
The statistics can be retrieved by:
$ cat /proc/timer_stats
While sampling is enabled, each readout from
/proc/timer_stats will see newly updated statistics. Once
sampling is disabled, the sampled information is kept
until a new sample period is started. This allows
multiple readouts.
Sample output from /proc/timer_stats:
$ cat /proc/timer_stats
Timer Stats Version: v0.3
Sample period: 1.764 s
Collection: active
255, 0 swapper/3 hrtimer_start_range_ns (tick_sched_timer)
71, 0 swapper/1 hrtimer_start_range_ns (tick_sched_timer)
58, 0 swapper/0 hrtimer_start_range_ns (tick_sched_timer)
4, 1694 gnome-shell mod_delayed_work_on (delayed_work_timer_fn)
17, 7 rcu_sched rcu_gp_kthread (process_timeout)
...
1, 4911 kworker/u16:0 mod_delayed_work_on (delayed_work_timer_fn)
1D, 2522 kworker/0:0 queue_delayed_work_on (delayed_work_timer_fn)
1029 total events, 583.333 events/sec
The output columns are:
* a count of the number of events, optionally (since
Linux 2.6.23) followed by the letter 'D' if this is a
deferrable timer;
* the PID of the process that initialized the timer;
* the name of the process that initialized the timer;
* the function where the timer was initialized; and
* (in parentheses) the callback function that is
associated with the timer.
During the Linux 4.11 development cycle, this file was
removed because of security concerns, as it exposes
information across namespaces. Furthermore, it is
possible to obtain the same information via in-kernel
tracing facilities such as ftrace.
/proc/tty
Subdirectory containing the pseudo-files and
subdirectories for tty drivers and line disciplines.
/proc/uptime
This file contains two numbers (values in seconds): the
uptime of the system (including time spent in suspend) and
the amount of time spent in the idle process.
/proc/version
This string identifies the kernel version that is
currently running. It includes the contents of
/proc/sys/kernel/ostype, /proc/sys/kernel/osrelease, and
/proc/sys/kernel/version. For example:
Linux version 1.0.9 (quinlan@phaze) #1 Sat May 14 01:51:54 EDT 1994
/proc/vmstat (since Linux 2.6.0)
This file displays various virtual memory statistics.
Each line of this file contains a single name-value pair,
delimited by white space. Some lines are present only if
the kernel was configured with suitable options. (In some
cases, the options required for particular files have
changed across kernel versions, so they are not listed
here. Details can be found by consulting the kernel
source code.) The following fields may be present:
nr_free_pages (since Linux 2.6.31)
nr_alloc_batch (since Linux 3.12)
nr_inactive_anon (since Linux 2.6.28)
nr_active_anon (since Linux 2.6.28)
nr_inactive_file (since Linux 2.6.28)
nr_active_file (since Linux 2.6.28)
nr_unevictable (since Linux 2.6.28)
nr_mlock (since Linux 2.6.28)
nr_anon_pages (since Linux 2.6.18)
nr_mapped (since Linux 2.6.0)
nr_file_pages (since Linux 2.6.18)
nr_dirty (since Linux 2.6.0)
nr_writeback (since Linux 2.6.0)
nr_slab_reclaimable (since Linux 2.6.19)
nr_slab_unreclaimable (since Linux 2.6.19)
nr_page_table_pages (since Linux 2.6.0)
nr_kernel_stack (since Linux 2.6.32)
Amount of memory allocated to kernel stacks.
nr_unstable (since Linux 2.6.0)
nr_bounce (since Linux 2.6.12)
nr_vmscan_write (since Linux 2.6.19)
nr_vmscan_immediate_reclaim (since Linux 3.2)
nr_writeback_temp (since Linux 2.6.26)
nr_isolated_anon (since Linux 2.6.32)
nr_isolated_file (since Linux 2.6.32)
nr_shmem (since Linux 2.6.32)
Pages used by shmem and tmpfs(5).
nr_dirtied (since Linux 2.6.37)
nr_written (since Linux 2.6.37)
nr_pages_scanned (since Linux 3.17)
numa_hit (since Linux 2.6.18)
numa_miss (since Linux 2.6.18)
numa_foreign (since Linux 2.6.18)
numa_interleave (since Linux 2.6.18)
numa_local (since Linux 2.6.18)
numa_other (since Linux 2.6.18)
workingset_refault (since Linux 3.15)
workingset_activate (since Linux 3.15)
workingset_nodereclaim (since Linux 3.15)
nr_anon_transparent_hugepages (since Linux 2.6.38)
nr_free_cma (since Linux 3.7)
Number of free CMA (Contiguous Memory Allocator)
pages.
nr_dirty_threshold (since Linux 2.6.37)
nr_dirty_background_threshold (since Linux 2.6.37)
pgpgin (since Linux 2.6.0)
pgpgout (since Linux 2.6.0)
pswpin (since Linux 2.6.0)
pswpout (since Linux 2.6.0)
pgalloc_dma (since Linux 2.6.5)
pgalloc_dma32 (since Linux 2.6.16)
pgalloc_normal (since Linux 2.6.5)
pgalloc_high (since Linux 2.6.5)
pgalloc_movable (since Linux 2.6.23)
pgfree (since Linux 2.6.0)
pgactivate (since Linux 2.6.0)
pgdeactivate (since Linux 2.6.0)
pgfault (since Linux 2.6.0)
pgmajfault (since Linux 2.6.0)
pgrefill_dma (since Linux 2.6.5)
pgrefill_dma32 (since Linux 2.6.16)
pgrefill_normal (since Linux 2.6.5)
pgrefill_high (since Linux 2.6.5)
pgrefill_movable (since Linux 2.6.23)
pgsteal_kswapd_dma (since Linux 3.4)
pgsteal_kswapd_dma32 (since Linux 3.4)
pgsteal_kswapd_normal (since Linux 3.4)
pgsteal_kswapd_high (since Linux 3.4)
pgsteal_kswapd_movable (since Linux 3.4)
pgsteal_direct_dma
pgsteal_direct_dma32 (since Linux 3.4)
pgsteal_direct_normal (since Linux 3.4)
pgsteal_direct_high (since Linux 3.4)
pgsteal_direct_movable (since Linux 2.6.23)
pgscan_kswapd_dma
pgscan_kswapd_dma32 (since Linux 2.6.16)
pgscan_kswapd_normal (since Linux 2.6.5)
pgscan_kswapd_high
pgscan_kswapd_movable (since Linux 2.6.23)
pgscan_direct_dma
pgscan_direct_dma32 (since Linux 2.6.16)
pgscan_direct_normal
pgscan_direct_high
pgscan_direct_movable (since Linux 2.6.23)
pgscan_direct_throttle (since Linux 3.6)
zone_reclaim_failed (since linux 2.6.31)
pginodesteal (since linux 2.6.0)
slabs_scanned (since linux 2.6.5)
kswapd_inodesteal (since linux 2.6.0)
kswapd_low_wmark_hit_quickly (since 2.6.33)
kswapd_high_wmark_hit_quickly (since 2.6.33)
pageoutrun (since Linux 2.6.0)
allocstall (since Linux 2.6.0)
pgrotated (since Linux 2.6.0)
drop_pagecache (since Linux 3.15)
drop_slab (since Linux 3.15)
numa_pte_updates (since Linux 3.8)
numa_huge_pte_updates (since Linux 3.13)
numa_hint_faults (since Linux 3.8)
numa_hint_faults_local (since Linux 3.8)
numa_pages_migrated (since Linux 3.8)
pgmigrate_success (since Linux 3.8)
pgmigrate_fail (since Linux 3.8)
compact_migrate_scanned (since Linux 3.8)
compact_free_scanned (since Linux 3.8)
compact_isolated (since Linux 3.8)
compact_stall (since Linux 2.6.35)
See the kernel source file
Documentation/admin-guide/mm/transhuge.rst.
compact_fail (since Linux 2.6.35)
See the kernel source file
Documentation/admin-guide/mm/transhuge.rst.
compact_success (since Linux 2.6.35)
See the kernel source file
Documentation/admin-guide/mm/transhuge.rst.
htlb_buddy_alloc_success (since Linux 2.6.26)
htlb_buddy_alloc_fail (since Linux 2.6.26)
unevictable_pgs_culled (since Linux 2.6.28)
unevictable_pgs_scanned (since Linux 2.6.28)
unevictable_pgs_rescued (since Linux 2.6.28)
unevictable_pgs_mlocked (since Linux 2.6.28)
unevictable_pgs_munlocked (since Linux 2.6.28)
unevictable_pgs_cleared (since Linux 2.6.28)
unevictable_pgs_stranded (since Linux 2.6.28)
thp_fault_alloc (since Linux 2.6.39)
See the kernel source file
Documentation/admin-guide/mm/transhuge.rst.
thp_fault_fallback (since Linux 2.6.39)
See the kernel source file
Documentation/admin-guide/mm/transhuge.rst.
thp_collapse_alloc (since Linux 2.6.39)
See the kernel source file
Documentation/admin-guide/mm/transhuge.rst.
thp_collapse_alloc_failed (since Linux 2.6.39)
See the kernel source file
Documentation/admin-guide/mm/transhuge.rst.
thp_split (since Linux 2.6.39)
See the kernel source file
Documentation/admin-guide/mm/transhuge.rst.
thp_zero_page_alloc (since Linux 3.8)
See the kernel source file
Documentation/admin-guide/mm/transhuge.rst.
thp_zero_page_alloc_failed (since Linux 3.8)
See the kernel source file
Documentation/admin-guide/mm/transhuge.rst.
balloon_inflate (since Linux 3.18)
balloon_deflate (since Linux 3.18)
balloon_migrate (since Linux 3.18)
nr_tlb_remote_flush (since Linux 3.12)
nr_tlb_remote_flush_received (since Linux 3.12)
nr_tlb_local_flush_all (since Linux 3.12)
nr_tlb_local_flush_one (since Linux 3.12)
vmacache_find_calls (since Linux 3.16)
vmacache_find_hits (since Linux 3.16)
vmacache_full_flushes (since Linux 3.19)
/proc/zoneinfo (since Linux 2.6.13)
This file displays information about memory zones. This
is useful for analyzing virtual memory behavior.
