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   xfs_io    ( 8 )

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FILE I/O COMMANDS

file [ N ] Display a list of all open files and (optionally) switch to an alternate current open file.

open [[ -acdfrstRTPL ] path ] Closes the current file, and opens the file specified by path instead. Without any arguments, displays statistics about the current file - see the stat command. -a opens append-only (O_APPEND). -d opens for direct I/O (O_DIRECT). -f creates the file if it doesn't already exist (O_CREAT). -r opens read-only (O_RDONLY). -s opens for synchronous I/O (O_SYNC). -t truncates on open (O_TRUNC). -n opens in non-blocking mode if possible (O_NONBLOCK). -T create a temporary file not linked into the filesystem namespace (O_TMPFILE). The pathname passed must refer to a directory which is treated as virtual parent for the newly created invisible file. Can not be used together with the -r option. -R marks the file as a realtime XFS file after opening it, if it is not already marked as such. -P opens the path as a referent only (O_PATH). This is incompatible with other flags specifying other O_xxx flags apart from -L. -L doesn't follow symlinks (O_NOFOLLOW). This is incompatible with other flags specifying other O_xxx flags apart from -P.

o See the open command.

close Closes the current open file, marking the next open file as current (if one exists).

c See the close command.

chmod -r | -w Change the mode of the currently open file. The -r option will set the file permissions to read-only (0444), whilst the -w option will set the file permissions to read-write (0644). This allows xfs_io to set up mismatches between the file permissions and the open file descriptor read/write mode to exercise permission checks inside various syscalls.

pread [ -b bsize ] [ -qv ] [ -FBR [ -Z seed ] ] [ -V vectors ] offset length Reads a range of bytes in a specified blocksize from the given offset. -b can be used to set the blocksize into which the read(2) requests will be split. The default blocksize is 4096 bytes. -q quiet mode, do not write anything to standard output. -v dump the contents of the buffer after reading, by default only the count of bytes actually read is dumped. -F read the buffers in a forward sequential direction. -B read the buffers in a reverse sequential direction. -R read the buffers in the give range in a random order. -Z seed specify the random number seed used for random reads. -V vectors Use the vectored IO read syscall preadv(2) with a number of blocksize length iovecs. The number of iovecs is set by the vectors parameter.

r See the pread command.

pwrite [ -i file ] [ -qdDwNOW ] [ -s skip ] [ -b size ] [ -S seed ] [ -FBR [ -Z zeed ] ] [ -V vectors ] offset length Writes a range of bytes in a specified blocksize from the given offset. The bytes written can be either a set pattern or read in from another file before writing. -i allows an input file to be specified as the source of the data to be written. -q quiet mode, do not write anything to standard output. -d causes direct I/O, rather than the usual buffered I/O, to be used when reading the input file. -w call fdatasync(2) once all writes are complete (included in timing results) -N Perform the pwritev2(2) call with RWF_NOWAIT. -D Perform the pwritev2(2) call with RWF_DSYNC. -O perform pwrite once and return the (maybe partial) bytes written. -W call fsync(2) once all writes are complete (included in timing results) -s specifies the number of bytes to skip from the start of the input file before starting to read. -b used to set the blocksize into which the write(2) requests will be split. The default blocksize is 4096 bytes. -S used to set the (repeated) fill pattern which is used when the data to write is not coming from a file. The default buffer fill pattern value is 0xcdcdcdcd. -F write the buffers in a forward sequential direction. -B write the buffers in a reverse sequential direction. -R write the buffers in the give range in a random order. -Z seed specify the random number seed used for random write -V vectors Use the vectored IO write syscall pwritev(2) with a number of blocksize length iovecs. The number of iovecs is set by the vectors parameter.

w See the pwrite command.

bmap [ -adelpv ] [ -n nx ] Prints the block mapping for the current open file. Refer to the xfs_bmap(8) manual page for complete documentation.

fiemap [ -alv ] [ -n nx ] [ offset [ len ]] Prints the block mapping for the current open file using the fiemap ioctl. Options behave as described in the xfs_bmap(8) manual page.

Optionally, this command also supports passing the start offset from where to begin the mapping and the length of that region. The kernel will return any full extents which intersect with the requested range, and the fiemap command will print them in their entirety. If the requested range starts or ends in a hole, fiemap will print the hole, truncated to the requested range.

extsize [ -R | -D ] [ value ] Display and/or modify the preferred extent size used when allocating space for the currently open file. If the -R option is specified, a recursive descent is performed for all directory entries below the currently open file (-D can be used to restrict the output to directories only). If the target file is a directory, then the inherited extent size is set for that directory (new files created in that directory inherit that extent size). The value should be specified in bytes, or using one of the usual units suffixes (k, m, g, b, etc). The extent size is always reported in units of bytes.

cowextsize [ -R | -D ] [ value ] Display and/or modify the preferred copy-on-write extent size used when allocating space for the currently open file. If the -R option is specified, a recursive descent is performed for all directory entries below the currently open file (-D can be used to restrict the output to directories only). If the target file is a directory, then the inherited CoW extent size is set for that directory (new files created in that directory inherit that CoW extent size). The value should be specified in bytes, or using one of the usual units suffixes (k, m, g, b, etc). The extent size is always reported in units of bytes.

allocsp size 0 Sets the size of the file to size and zeroes any additional space allocated using the XFS_IOC_ALLOCSP/XFS_IOC_FREESP system call described in the xfsctl(3) manual page. allocsp and freesp do exactly the same thing.

freesp size 0 See the allocsp command.

fadvise [ -r | -s | [[ -d | -n | -w ] offset length ]] On platforms which support it, allows hints be given to the system regarding the expected I/O patterns on the file. The range arguments are required by some advise commands ([*] below), and the others must have no range arguments. With no arguments, the POSIX_FADV_NORMAL advice is implied (default readahead). -d the data will not be accessed again in the near future (POSIX_FADV_DONTNEED[*]). -n data will be accessed once and not be reused (POSIX_FADV_NOREUSE[*]). -r expect access to data in random order (POSIX_FADV_RANDOM), which sets readahead to zero. -s expect access to data in sequential order (POSIX_FADV_SEQUENTIAL), which doubles the default readahead on the file. -w advises the specified data will be needed again (POSIX_FADV_WILLNEED[*]) which forces the maximum readahead.

fdatasync Calls fdatasync(2) to flush the file's in-core data to disk.

fsync Calls fsync(2) to flush all in-core file state to disk.

s See the fsync command.

sync_range [ -a | -b | -w ] offset length On platforms which support it, allows control of syncing a range of the file to disk. With no options, SYNC_FILE_RANGE_WRITE is implied on the range supplied. -a wait for IO in the given range to finish after writing (SYNC_FILE_RANGE_WAIT_AFTER). -b wait for IO in the given range to finish before writing (SYNC_FILE_RANGE_WAIT_BEFORE). -w start writeback of dirty data in the given range (SYNC_FILE_RANGE_WRITE).

sync Calls sync(2) to flush all filesystems' in-core data to disk.

syncfs Calls syncfs(2) to flush this filesystem's in-core data to disk.

resvsp offset length Allocates reserved, unwritten space for part of a file using the XFS_IOC_RESVSP system call described in the xfsctl(3) manual page.

unresvsp offset length Frees reserved space for part of a file using the XFS_IOC_UNRESVSP system call described in the xfsctl(3) manual page.

falloc [ -k ] offset length Allocates reserved, unwritten space for part of a file using the fallocate routine as described in the fallocate(2) manual page. -k will set the FALLOC_FL_KEEP_SIZE flag as described in fallocate(2).

fcollapse offset length Call fallocate with FALLOC_FL_COLLAPSE_RANGE flag as described in the fallocate(2) manual page to de-allocates blocks and eliminates the hole created in this process by shifting data blocks into the hole.

finsert offset length Call fallocate with FALLOC_FL_INSERT_RANGE flag as described in the fallocate(2) manual page to create the hole by shifting data blocks.

fpunch offset length Punches (de-allocates) blocks in the file by calling fallocate with the FALLOC_FL_PUNCH_HOLE flag as described in the fallocate(2) manual page.

funshare offset length Call fallocate with FALLOC_FL_UNSHARE_RANGE flag as described in the fallocate(2) manual page to unshare all shared blocks within the range.

fzero [ -k ] offset length Call fallocate with FALLOC_FL_ZERO_RANGE flag as described in the fallocate(2) manual page to allocate and zero blocks within the range. With the -k option, use the FALLOC_FL_KEEP_SIZE flag as well.

zero offset length Call xfsctl with XFS_IOC_ZERO_RANGE as described in the xfsctl(3) manual page to allocate and zero blocks within the range.

truncate offset Truncates the current file at the given offset using ftruncate(2).

sendfile [ -q ] -i srcfile | -f N [ offset length ] On platforms which support it, allows a direct in-kernel copy between two file descriptors. The current open file is the target, the source must be specified as another open file (-f) or by path (-i). -q quiet mode, do not write anything to standard output.

readdir [ -v ] [ -o offset ] [ -l length ] Read a range of directory entries from a given offset of a directory. -v verbose mode - dump dirent content as defined in readdir(3) -o specify starting offset -l specify total length to read (in bytes)

seek -a | -d | -h [ -r ] [ -s ] offset On platforms that support the lseek(2) SEEK_DATA and SEEK_HOLE options, display the offsets of the specified segments. -a Display both data and hole segments starting at the specified offset. -d Display the data segment starting at the specified offset. -h Display the hole segment starting at the specified offset. -r Recursively display all the specified segments starting at the specified offset. -s Display the starting lseek(2) offset. This offset will be a calculated value when both data and holes are displayed together or performing a recusively display.

reflink [ -C ] [ -q ] src_file [src_offset dst_offset length] On filesystems that support the FICLONERANGE or BTRFS_IOC_CLONE_RANGE ioctls, map length bytes at offset dst_offset in the open file to the same physical blocks that are mapped at offset src_offset in the file src_file , replacing any contents that may already have been there. If a program writes into a reflinked block range of either file, the dirty blocks will be cloned, written to, and remapped ("copy on write") in the affected file, leaving the other file(s) unchanged. If src_offset, dst_offset, and length are omitted, all contents of src_file will be reflinked into the open file. -C Print timing statistics in a condensed format. -q Do not print timing statistics at all.

dedupe [ -C ] [ -q ] src_file src_offset dst_offset length On filesystems that support the FIDEDUPERANGE or BTRFS_IOC_FILE_EXTENT_SAME ioctls, map length bytes at offset dst_offset in the open file to the same physical blocks that are mapped at offset src_offset in the file src_file , but only if the contents of both ranges are identical. This is known as block-based deduplication. If a program writes into a reflinked block range of either file, the dirty blocks will be cloned, written to, and remapped ("copy on write") in the affected file, leaving the other file(s) unchanged. -C Print timing statistics in a condensed format. -q Do not print timing statistics at all.

copy_range [ -s src_offset ] [ -d dst_offset ] [ -l length ] src_file | -f N On filesystems that support the copy_file_range(2) system call, copies data from the source file into the current open file. The source must be specified either by path (src_file) or as another open file (-f). If length is not specified, this command copies data from src_offset to the end of src_file into the dst_file at dst_offset. -s Copy data from src_file beginning from src_offset. -d Copy data into the open file beginning at dst_offset. -l Copy up to length bytes of data.

swapext donor_file Swaps extent forks between files. The current open file is the target. The donor file is specified by path. Note that file data is not copied (file content moves with the fork(s)).

set_encpolicy [ -c mode ] [ -n mode ] [ -f flags ] [ -v version ] [ keyspec ] On filesystems that support encryption, assign an encryption policy to the current file. keyspec is a hex string which specifies the encryption key to use. For v1 encryption policies, keyspec must be a 16-character hex string (8 bytes). For v2 policies, keyspec must be a 32-character hex string (16 bytes). If unspecified, an all-zeroes value is used. -c mode contents encryption mode (e.g. AES-256-XTS) -n mode filenames encryption mode (e.g. AES-256-CTS) -f flags policy flags (numeric) -v version policy version. Defaults to 1 or 2 depending on the length of keyspec; or to 1 if keyspec is unspecified.

get_encpolicy [ -1 ] [ -t ] On filesystems that support encryption, display the encryption policy of the current file. -1 Use only the old ioctl to get the encryption policy. This only works if the file has a v1 encryption policy. -t Test whether v2 encryption policies are supported. Prints "supported", "unsupported", or an error message.

add_enckey [ -d descriptor ] [ -k key_id ] On filesystems that support encryption, add an encryption key to the filesystem containing the currently open file. By default, the raw key in binary (typically 64 bytes long) is read from standard input. -d descriptor key descriptor, as a 16-character hex string (8 bytes). If given, the key will be available for use by v1 encryption policies that use this descriptor. Otherwise, the key is added as a v2 policy key, and on success the resulting "key identifier" will be printed. -k key_id ID of kernel keyring key of type "fscrypt- provisioning". If given, the raw key will be taken from here rather than from standard input.

rm_enckey [ -a ] keyspec On filesystems that support encryption, remove an encryption key from the filesystem containing the currently open file. keyspec is a hex string specifying the key to remove, as a 16-character "key descriptor" or a 32-character "key identifier". -a Remove the key for all users who have added it, not just the current user. This is a privileged operation.

enckey_status keyspec On filesystems that support encryption, display the status of an encryption key. keyspec is a hex string specifying the key for which to display the status, as a 16-character "key descriptor" or a 32-character "key identifier".

lsattr [ -R | -D | -a | -v ] List extended inode flags on the currently open file. If the -R option is specified, a recursive descent is performed for all directory entries below the currently open file (-D can be used to restrict the output to directories only). This is a depth first descent, it does not follow symlinks and it also does not cross mount points.

The current inode flag letters are documented below. Please refer to the ioctl_xfs_fsgetxattr(2) documentation for more details about what they mean.

r realtime file (XFS_XFLAG_REALTIME)

p prealloc (XFS_XFLAG_PREALLOC)

i immutable (XFS_XFLAG_IMMUTABLE)

a append only (XFS_XFLAG_APPEND)

s synchronous file writes (XFS_XFLAG_SYNC)

A noatime (XFS_XFLAG_NOATIME)

d nodump (XFS_XFLAG_NODUMP)

t inherit realtime flag (XFS_XFLAG_RTINHERIT)"

P inherit project id (XFS_XFLAG_PROJINHERIT)

n no symlink creation (XFS_XFLAG_NOSYMLINKS)

e extent size hint (XFS_XFLAG_EXTSIZE)

E inherit extent size hint (XFS_XFLAG_EXTSZINHERIT)

f nodefrag (XFS_XFLAG_NODEFRAG)

S filestream allocator (XFS_XFLAG_FILESTREAM)

x direct access persistent memory (XFS_XFLAG_DAX)

C copy on write extent hint (XFS_XFLAG_COWEXTSIZE)

X has extended attributes (XFS_XFLAG_HASATTR)

chattr [ -R | -D ] [ +/-riasAdtPneEfSxC ] Change extended inode flags on the currently open file. The -R and -D options have the same meaning as above.

See the lsattr command above for the list of inode flag letters.

flink path Link the currently open file descriptor into the filesystem namespace. stat [ -v|-r ] Selected statistics from stat(2) and the XFS_IOC_GETXATTR system call on the current file. If the -v option is specified, the atime (last access), mtime (last modify), and ctime (last change) timestamps are also displayed. The -r option dumps raw fields from the stat structure. statx [ -v|-r ][ -m basic | -m all | -m <mask> ][ -FD ] Selected statistics from stat(2) and the XFS_IOC_GETXATTR system call on the current file. -v Show timestamps. -r Dump raw statx structure values. -m basic Set the field mask for the statx call to STATX_BASIC_STATS. -m all Set the the field mask for the statx call to STATX_ALL (default). -m <mask> Specify a numeric field mask for the statx call. -F Force the attributes to be synced with the server. -D Don't sync attributes with the server.

chproj [ -R|-D ] Modifies the project identifier associated with the current path. The -R option will recursively descend if the current path is a directory. The -D option will also recursively descend, only setting modifying projects on subdirectories. See the xfs_quota(8) manual page for more information about project identifiers.

lsproj [ -R|-D ] Displays the project identifier associated with the current path. The -R and -D options behave as described above, in chproj.

parent [ -cpv ] By default this command prints out the parent inode numbers, inode generation numbers and basenames of all the hardlinks which point to the inode of the current file. -p the output is similar to the default output except pathnames up to the mount-point are printed out instead of the component name. -c the file's filesystem will check all the parent attributes for consistency. -v verbose output will be printed. [NOTE: Not currently operational on Linux.]

utimes atime_sec atime_nsec mtime_sec mtime_nsec The utimes command changes the atime and mtime of the current file. sec uses UNIX timestamp notation and is the seconds elapsed since 1970-01-01 00:00:00 UTC. nsec is the nanoseconds since the sec. This value needs to be in the range 0-999999999 with UTIME_NOW and UTIME_OMIT being exceptions. Each (sec, nsec) pair constitutes a single timestamp value.