-c max-mount-counts
Adjust the number of mounts after which the file system
will be checked by e2fsck(8). If max-mount-counts is the
string "random", tune2fs will use a random value between
20 and 40. If max-mount-counts is 0 or -1, the number of
times the file system is mounted will be disregarded by
e2fsck(8) and the kernel.
Staggering the mount-counts at which file systems are
forcibly checked will avoid all file systems being checked
at one time when using journaled file systems.
Mount-count-dependent checking is disabled by default to
avoid unanticipated long reboots while e2fsck does its
work. If you are concerned about file system corruptions
caused by potential hardware problems of kernel bugs, a
better solution than mount-count-dependent checking is to
use the e2scrub(8) program. This does require placing the
file system on an LVM volume, however.
-C mount-count
Set the number of times the file system has been mounted.
If set to a greater value than the max-mount-counts
parameter set by the -c option, e2fsck(8) will check the
file system at the next reboot.
-e error-behavior
Change the behavior of the kernel code when errors are
detected. In all cases, a file system error will cause
e2fsck(8) to check the file system on the next boot.
error-behavior can be one of the following:
continue
Continue normal execution.
remount-ro
Remount file system read-only.
panic Cause a kernel panic.
-E extended-options
Set extended options for the file system. Extended
options are comma separated, and may take an argument
using the equals ('=') sign. The following extended
options are supported:
clear_mmp
Reset the MMP block (if any) back to the clean
state. Use only if absolutely certain the
device is not currently mounted or being
fscked, or major file system corruption can
result. Needs '-f'.
mmp_update_interval=interval
Adjust the initial MMP update interval to
interval seconds. Specifying an interval of 0
means to use the default interval. The
specified interval must be less than 300
seconds. Requires that the mmp feature be
enabled.
stride=stride-size
Configure the file system for a RAID array
with stride-size file system blocks. This is
the number of blocks read or written to disk
before moving to next disk. This mostly
affects placement of file system metadata like
bitmaps at mke2fs(2) time to avoid placing
them on a single disk, which can hurt the
performance. It may also be used by block
allocator.
stripe_width=stripe-width
Configure the file system for a RAID array
with stripe-width file system blocks per
stripe. This is typically be stride-size * N,
where N is the number of data disks in the
RAID (e.g. RAID 5 N+1, RAID 6 N+2). This
allows the block allocator to prevent read-
modify-write of the parity in a RAID stripe if
possible when the data is written.
hash_alg=hash-alg
Set the default hash algorithm used for file
systems with hashed b-tree directories. Valid
algorithms accepted are: legacy, half_md4, and
tea.
encoding=encoding-name
Enable the casefold feature in the super block
and set encoding-name as the encoding to be
used. If encoding-name is not specified, utf8
is used. The encoding cannot be altered if
casefold was previously enabled.
encoding_flags=encoding-flags
Define parameters for file name character
encoding operations. If a flag is not changed
using this parameter, its default value is
used. encoding-flags should be a comma-
separated lists of flags to be enabled. The
flags cannot be altered if casefold was
previously enabled.
The only flag that can be set right now is
strict which means that invalid strings should
be rejected by the file system. In the
default configuration, the strict flag is
disabled.
mount_opts=mount_option_string
Set a set of default mount options which will
be used when the file system is mounted.
Unlike the bitmask-based default mount options
which can be specified with the -o option,
mount_option_string is an arbitrary string
with a maximum length of 63 bytes, which is
stored in the superblock.
The ext4 file system driver will first apply
the bitmask-based default options, and then
parse the mount_option_string, before parsing
the mount options passed from the mount(8)
program.
This superblock setting is only honored in
2.6.35+ kernels; and not at all by the ext2
and ext3 file system drivers.
force_fsck
Set a flag in the file system superblock
indicating that errors have been found. This
will force fsck to run at the next mount.
test_fs
Set a flag in the file system superblock
indicating that it may be mounted using
experimental kernel code, such as the ext4dev
file system.
^test_fs
Clear the test_fs flag, indicating the file
system should only be mounted using
production-level file system code.
-f Force the tune2fs operation to complete even in the face
of errors. This option is useful when removing the
has_journal file system feature from a file system which
has an external journal (or is corrupted such that it
appears to have an external journal), but that external
journal is not available. If the file system appears to
require journal replay, the -f flag must be specified
twice to proceed.
WARNING: Removing an external journal from a file system
which was not cleanly unmounted without first replaying
the external journal can result in severe data loss and
file system corruption.
-g group
Set the group which can use the reserved file system
blocks. The group parameter can be a numerical gid or a
group name. If a group name is given, it is converted to
a numerical gid before it is stored in the superblock.
-i interval-between-checks[d|m|w]
Adjust the maximal time between two file system checks.
No suffix or d will interpret the number interval-between-
checks as days, m as months, and w as weeks. A value of
zero will disable the time-dependent checking.
There are pros and cons to disabling these periodic
checks; see the discussion under the -c (mount-count-
dependent check) option for details.
-I Change the inode size used by the file system. This
requires rewriting the inode table, so it requires that
the file system is checked for consistency first using
e2fsck(8). This operation can also take a while and the
file system can be corrupted and data lost if it is
interrupted while in the middle of converting the file
system. Backing up the file system before changing inode
size is recommended.
File systems with an inode size of 128 bytes do not
support timestamps beyond January 19, 2038. Inodes which
are 256 bytes or larger will support extended timestamps,
project id's, and the ability to store some extended
attributes in the inode table for improved performance.
-j Add an ext3 journal to the file system. If the -J option
is not specified, the default journal parameters will be
used to create an appropriately sized journal (given the
size of the file system) stored within the file system.
Note that you must be using a kernel which has ext3
support in order to actually make use of the journal.
If this option is used to create a journal on a mounted
file system, an immutable file, .journal, will be created
in the top-level directory of the file system, as it is
the only safe way to create the journal inode while the
file system is mounted. While the ext3 journal is
visible, it is not safe to delete it, or modify it while
the file system is mounted; for this reason the file is
marked immutable. While checking unmounted file systems,
e2fsck(8) will automatically move .journal files to the
invisible, reserved journal inode. For all file systems
except for the root file system, this should happen
automatically and naturally during the next reboot cycle.
Since the root file system is mounted read-only, e2fsck(8)
must be run from a rescue floppy in order to effect this
transition.
On some distributions, such as Debian, if an initial
ramdisk is used, the initrd scripts will automatically
convert an ext2 root file system to ext3 if the /etc/fstab
file specifies the ext3 file system for the root file
system in order to avoid requiring the use of a rescue
floppy to add an ext3 journal to the root file system.
-J journal-options
Override the default ext3 journal parameters. Journal
options are comma separated, and may take an argument
using the equals ('=') sign. The following journal
options are supported:
size=journal-size
Create a journal stored in the file system of
size journal-size megabytes. The size of the
journal must be at least 1024 file system
blocks (i.e., 1MB if using 1k blocks, 4MB if
using 4k blocks, etc.) and may be no more
than 10,240,000 file system blocks. There
must be enough free space in the file system
to create a journal of that size.
fast_commit_size=fast-commit-size
Create an additional fast commit journal area
of size fast-commit-size kilobytes. This
option is only valid if fast_commit feature is
enabled on the file system. If this option is
not specified and if fast_commit feature is
turned on, fast commit area size defaults to
journal-size / 64 megabytes. The total size of
the journal with fast_commit feature set is
journal-size + ( fast-commit-size * 1024)
megabytes. The total journal size may be no
more than 10,240,000 file system blocks or
half the total file system size (whichever is
smaller).
location=journal-location
Specify the location of the journal. The
argument journal-location can either be
specified as a block number, or if the number
has a units suffix (e.g., 'M', 'G', etc.)
interpret it as the offset from the beginning
of the file system.
device=external-journal
Attach the file system to the journal block
device located on external-journal. The
external journal must have been already
created using the command
mke2fs -O journal_dev external-journal
Note that external-journal must be formatted
with the same block size as file systems which
will be using it. In addition, while there is
support for attaching multiple file systems to
a single external journal, the Linux kernel
and e2fsck(8) do not currently support shared
external journals yet.
Instead of specifying a device name directly,
external-journal can also be specified by
either LABEL=label or UUID=UUID to locate the
external journal by either the volume label or
UUID stored in the ext2 superblock at the
start of the journal. Use dumpe2fs(8) to
display a journal device's volume label and
UUID. See also the -L option of tune2fs(8).
Only one of the size or device options can be given for a
file system.
-l List the contents of the file system superblock, including
the current values of the parameters that can be set via
this program.
-L volume-label
Set the volume label of the file system. Ext2 file system
labels can be at most 16 characters long; if volume-label
is longer than 16 characters, tune2fs will truncate it and
print a warning. The volume label can be used by
mount(8), fsck(8), and /etc/fstab(5) (and possibly others)
by specifying LABEL=volume-label instead of a block
special device name like /dev/hda5.
-m reserved-blocks-percentage
Set the percentage of the file system which may only be
allocated by privileged processes. Reserving some number
of file system blocks for use by privileged processes is
done to avoid file system fragmentation, and to allow
system daemons, such as syslogd(8), to continue to
function correctly after non-privileged processes are
prevented from writing to the file system. Normally, the
default percentage of reserved blocks is 5%.
-M last-mounted-directory
Set the last-mounted directory for the file system.
-o [^]mount-option[,...]
Set or clear the indicated default mount options in the
file system. Default mount options can be overridden by
mount options specified either in /etc/fstab(5) or on the
command line arguments to mount(8). Older kernels may not
support this feature; in particular, kernels which predate
2.4.20 will almost certainly ignore the default mount
options field in the superblock.
More than one mount option can be cleared or set by
separating features with commas. Mount options prefixed
with a caret character ('^') will be cleared in the file
system's superblock; mount options without a prefix
character or prefixed with a plus character ('+') will be
added to the file system.
The following mount options can be set or cleared using
tune2fs:
debug Enable debugging code for this file system.
bsdgroups
Emulate BSD behavior when creating new files:
they will take the group-id of the directory
in which they were created. The standard
System V behavior is the default, where newly
created files take on the fsgid of the current
process, unless the directory has the setgid
bit set, in which case it takes the gid from
the parent directory, and also gets the setgid
bit set if it is a directory itself.
user_xattr
Enable user-specified extended attributes.
acl Enable Posix Access Control Lists.
uid16 Disables 32-bit UIDs and GIDs. This is for
interoperability with older kernels which only
store and expect 16-bit values.
journal_data
When the file system is mounted with
journaling enabled, all data (not just
metadata) is committed into the journal prior
to being written into the main file system.
journal_data_ordered
When the file system is mounted with
journaling enabled, all data is forced
directly out to the main file system prior to
its metadata being committed to the journal.
journal_data_writeback
When the file system is mounted with
journaling enabled, data may be written into
the main file system after its metadata has
been committed to the journal. This may
increase throughput, however, it may allow old
data to appear in files after a crash and
journal recovery.
nobarrier
The file system will be mounted with barrier
operations in the journal disabled. (This
option is currently only supported by the ext4
file system driver in 2.6.35+ kernels.)
block_validity
The file system will be mounted with the
block_validity option enabled, which causes
extra checks to be performed after reading or
writing from the file system. This prevents
corrupted metadata blocks from causing file
system damage by overwriting parts of the
inode table or block group descriptors. This
comes at the cost of increased memory and CPU
overhead, so it is enabled only for debugging
purposes. (This option is currently only
supported by the ext4 file system driver in
2.6.35+ kernels.)
discard
The file system will be mounted with the
discard mount option. This will cause the
file system driver to attempt to use the
trim/discard feature of some storage devices
(such as SSD's and thin-provisioned drives
available in some enterprise storage arrays)
to inform the storage device that blocks
belonging to deleted files can be reused for
other purposes. (This option is currently
only supported by the ext4 file system driver
in 2.6.35+ kernels.)
nodelalloc
The file system will be mounted with the
nodelalloc mount option. This will disable
the delayed allocation feature. (This option
is currently only supported by the ext4 file
system driver in 2.6.35+ kernels.)
-O [^]feature[,...]
Set or clear the indicated file system features (options)
in the file system. More than one file system feature can
be cleared or set by separating features with commas.
File System features prefixed with a caret character ('^')
will be cleared in the file system's superblock; file
system features without a prefix character or prefixed
with a plus character ('+') will be added to the file
system. For a detailed description of the file system
features, please see the man page ext4(5).
The following file system features can be set or cleared
using tune2fs:
64bit Enable the file system to be larger than 2^32
blocks.
casefold
Enable support for file system level
casefolding. Tune2fs currently only supports
setting this file system feature.
dir_index
Use hashed b-trees to speed up lookups for
large directories.
dir_nlink
Allow more than 65000 subdirectories per
directory.
ea_inode
Allow the value of each extended attribute to
be placed in the data blocks of a separate
inode if necessary, increasing the limit on
the size and number of extended attributes per
file. Tune2fs currently only supports setting
this file system feature.
encrypt
Enable support for file system level
encryption. Tune2fs currently only supports
setting this file system feature.
extent Enable the use of extent trees to store the
location of data blocks in inodes. Tune2fs
currently only supports setting this file
system feature.
extra_isize
Enable the extended inode fields used by ext4.
filetype
Store file type information in directory
entries.
flex_bg
Allow bitmaps and inode tables for a block
group to be placed anywhere on the storage
media. Tune2fs will not reorganize the
location of the inode tables and allocation
bitmaps, as mke2fs(8) will do when it creates
a freshly formatted file system with flex_bg
enabled.
has_journal
Use a journal to ensure file system
consistency even across unclean shutdowns.
Setting the file system feature is equivalent
to using the -j option.
fast_commit
Enable fast commit journaling feature to
improve fsync latency.
large_dir
Increase the limit on the number of files per
directory. Tune2fs currently only supports
setting this file system feature.
huge_file
Support files larger than 2 terabytes in size.
large_file
File System can contain files that are greater
than 2GB.
metadata_csum
Store a checksum to protect the contents in
each metadata block.
metadata_csum_seed
Allow the file system to store the metadata
checksum seed in the superblock, enabling the
administrator to change the UUID of a file
system using the metadata_csum feature while
it is mounted.
mmp Enable or disable multiple mount protection
(MMP) feature.
project
Enable project ID tracking. This is used for
project quota tracking.
quota Enable internal file system quota inodes.
read-only
Force the kernel to mount the file system
read-only.
resize_inode
Reserve space so the block group descriptor
table may grow in the future. Tune2fs only
supports clearing this file system feature.
sparse_super
Limit the number of backup superblocks to save
space on large file systems. Tune2fs
currently only supports setting this file
system feature.
stable_inodes
Prevent the file system from being shrunk or
having its UUID changed, in order to allow the
use of specialized encryption settings that
make use of the inode numbers and UUID.
Tune2fs currently only supports setting this
file system feature.
uninit_bg
Allow the kernel to initialize bitmaps and
inode tables lazily, and to keep a high
watermark for the unused inodes in a file
system, to reduce e2fsck(8) time. The first
e2fsck run after enabling this feature will
take the full time, but subsequent e2fsck runs
will take only a fraction of the original
time, depending on how full the file system
is.
verity Enable support for verity protected files.
Tune2fs currently only supports setting this
file system feature.
After setting or clearing sparse_super, uninit_bg,
filetype, or resize_inode file system features, the file
system may require being checked using e2fsck(8) to return
the file system to a consistent state. Tune2fs will print
a message requesting that the system administrator run
e2fsck(8) if necessary. After setting the dir_index
feature, e2fsck -D can be run to convert existing
directories to the hashed B-tree format. Enabling certain
file system features may prevent the file system from
being mounted by kernels which do not support those
features. In particular, the uninit_bg and flex_bg
features are only supported by the ext4 file system.
-r reserved-blocks-count
Set the number of reserved file system blocks.
-Q quota-options
Sets 'quota' feature on the superblock and works on the
quota files for the given quota type. Quota options could
be one or more of the following:
[^]usrquota
Sets/clears user quota inode in the
superblock.
[^]grpquota
Sets/clears group quota inode in the
superblock.
[^]prjquota
Sets/clears project quota inode in the
superblock.
-T time-last-checked
Set the time the file system was last checked using
e2fsck. The time is interpreted using the current (local)
timezone. This can be useful in scripts which use a
Logical Volume Manager to make a consistent snapshot of a
file system, and then check the file system during off
hours to make sure it hasn't been corrupted due to
hardware problems, etc. If the file system was clean,
then this option can be used to set the last checked time
on the original file system. The format of time-last-
checked is the international date format, with an optional
time specifier, i.e. YYYYMMDD[HH[MM[SS]]]. The keyword
now is also accepted, in which case the last checked time
will be set to the current time.
-u user
Set the user who can use the reserved file system blocks.
user can be a numerical uid or a user name. If a user
name is given, it is converted to a numerical uid before
it is stored in the superblock.
-U UUID
Set the universally unique identifier (UUID) of the file
system to UUID. The format of the UUID is a series of hex
digits separated by hyphens, like this:
"c1b9d5a2-f162-11cf-9ece-0020afc76f16". The UUID
parameter may also be one of the following:
clear clear the file system UUID
random generate a new randomly-generated UUID
time generate a new time-based UUID
The UUID may be used by mount(8), fsck(8), and
/etc/fstab(5) (and possibly others) by specifying
UUID=uuid instead of a block special device name like
/dev/hda1.
See uuidgen(8) for more information. If the system does
not have a good random number generator such as
/dev/random or /dev/urandom, tune2fs will automatically
use a time-based UUID instead of a randomly-generated
UUID.
-z undo_file
Before overwriting a file system block, write the old
contents of the block to an undo file. This undo file can
be used with e2undo(8) to restore the old contents of the
file system should something go wrong. If the empty
string is passed as the undo_file argument, the undo file
will be written to a file named tune2fs-device.e2undo in
the directory specified via the E2FSPROGS_UNDO_DIR
environment variable.
WARNING: The undo file cannot be used to recover from a
power or system crash.
