xfs_io(8) - man - phpMan

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xfs_io(8) System Manager's Manual xfs_io(8)

NAME
xfs_io - debug the I/O path of an XFS filesystem

SYNOPSIS
xfs_io [ -adfimrRstxT ] [ -c cmd ] ... [ -C cmd ] ... [ -p prog ] [ file ]
xfs_io -V

DESCRIPTION
xfs_io is a debugging tool like xfs_db(8), but is aimed at examining the regular file I/O
paths rather than the raw XFS volume itself. These code paths include not only the obvious
read/write/mmap interfaces for manipulating files, but also cover all of the XFS extensions
(such as space preallocation, additional inode flags, etc).

OPTIONS
xfs_io commands may be run interactively (the default) or as arguments on the command line.
Interactive mode always runs commands on the current open file, whilst commands run from the
command line may be repeated on all open files rather than just the current open file. In
general, open file iteration will occur for commands that operate on file content or state.
In contrast, commands that operate on filesystem or system-wide state will only be run on the
current file regardless of how many files are currently open. Multiple arguments may be
given on the command line and they are run in the sequence given. The program exits one all
commands have been run.

-c cmd Run the specified command on all currently open files. To maintain compatibility
with historical usage, commands that can not be run on all open files will still be
run but only execute once on the current open file. Multiple -c arguments may be
given and may be interleaved on the command line in any order with -C commands.

-C cmd Run the specified command only on the current open file. Multiple -C arguments may
be given and may be interleaved on the command line in any order with -c commands.

-p prog Set the program name for prompts and some error messages, the default value is
xfs_io.

-f Create file if it does not already exist.

-r Open file read-only, initially. This is required if file is immutable or append-
only.

-i Start an idle thread. The purpose of this idle thread is to test io from a multi
threaded process. With single threaded process, the file table is not shared and
file structs are not reference counted. Spawning an idle thread can help detecting
file struct reference leaks.

-x Expert mode. Dangerous commands are only available in this mode. These commands
also tend to require additional privileges.

-V Prints the version number and exits.

The other open(2) options described below are also available from the command line.

CONCEPTS
xfs_io maintains a number of open files and memory mappings. Files can be initially opened
on the command line (optionally), and additional files can also be opened later.

xfs_io commands can be broken up into three groups. Some commands are aimed at doing regular
file I/O - read, write, sync, space preallocation, etc.

The second set of commands exist for manipulating memory mapped regions of a file - mapping,
accessing, storing, unmapping, flushing, etc.

The remaining commands are for the navigation and display of data structures relating to the
open files, mappings, and the filesystems where they reside.

Many commands have extensive online help. Use the help command for more details on any com‐
mand.

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 ar‐
guments, 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 par‐
ent 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 permis‐
sions 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 inher‐
ited extent size is set for that directory (new files created in that directory in‐
herit 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 di‐
rectory inherit that CoW extent size). The value should be specified in bytes, or us‐
ing one of the usual units suffixes (k, m, g, b, etc). The extent size is always re‐
ported 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 ex‐
pected I/O patterns on the file. The range arguments are required by some advise com‐
mands ([*] 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_DONT‐
NEED[*]).
-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 dou‐
bles 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 de‐
scribed 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) man‐
ual page to create the hole by shifting data blocks.

fpunch offset length
Punches (de-allocates) blocks in the file by calling fallocate with the FAL‐
LOC_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) man‐
ual 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 FAL‐
LOC_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 allo‐
cate 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 de‐
scriptors. The current open file is the target, the source must be specified as an‐
other 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 off‐‐
set.
-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 dis‐
play.

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 pro‐
gram 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 en‐
cryption policies, keyspec must be a 16-character hex string (8 bytes). For v2 poli‐
cies, 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", "unsup‐
ported", or an error message.

add_enckey [ -d descriptor ] [ -k key_id ]
On filesystems that support encryption, add an encryption key to the filesystem con‐
taining 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. Oth‐
erwise, 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 re‐
move, 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 recur‐
sively 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 op‐
tions 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.

MEMORY MAPPED I/O COMMANDS
mmap [ N | [[ -rwxS ] [-s size ] offset length ]]
With no arguments, mmap shows the current mappings. Specifying a single numeric argu‐
ment N sets the current mapping. If two arguments are specified (a range specified by
offset and length), a new mapping is created spanning the range, and the protection
mode can be given as a combination of PROT_READ (-r), PROT_WRITE (-w), and PROT_EXEC
(-x). The mapping will be created with the MAP_SHARED flag by default, or with the
Linux specific (MAP_SYNC | MAP_SHARED_VALIDATE) flags if -S is given. -s size is used
to do a mmap(size) && munmap(size) operation at first, try to reserve some extendible
free memory space, if size is bigger than length parameter. But there's not guarantee
that the memory after length ( up to size ) will stay free. e.g. "mmap -rw -s 8192
1024" will mmap 0 ~ 1024 bytes memory, but try to reserve 1024 ~ 8192 free space(no
guarantee). This free space will helpful for "mremap 8192" without MREMAP_MAYMOVE
flag.

mm See the mmap command.

mremap [ -f <new_address> ] [ -m ] new_length
Changes the current mapping size to new_length. Whether the mapping may be moved is
controlled by the flags passed; MREMAP_FIXED (-f), or MREMAP_MAYMOVE (-m). new_length
specifies a page-aligned address to which the mapping must be moved. It can be set to
139946004389888, 4096k or 1g etc.

mrm See the mremap command.

munmap Unmaps the current memory mapping.

mu See the munmap command.

mread [ -f | -v ] [ -r ] [ offset length ]
Accesses a segment of the current memory mapping, optionally dumping it to the stan‐
dard output stream (with -v or -f option) for inspection. The accesses are performed
sequentially from the start offset by default, but can also be done from the end back‐
wards through the mapping if the -r option in specified. The two verbose modes differ
only in the relative offsets they display, the -f option is relative to file start,
whereas -v shows offsets relative to the start of the mapping.

mr See the mread command.

mwrite [ -r ] [ -S seed ] [ offset length ]
Stores a byte into memory for a range within a mapping. The default stored value is
'X', repeated to fill the range specified, but this can be changed using the -S op‐
tion. The memory stores are performed sequentially from the start offset by default,
but can also be done from the end backwards through the mapping if the -r option in
specified.

mw See the mwrite command.

msync [ -i ] [ -a | -s ] [ offset length ]
Writes all modified copies of pages over the specified range (or entire mapping if no
range specified) to their backing storage locations. Also, optionally invalidates
(-i) so that subsequent references to the pages will be obtained from their backing
storage locations (instead of cached copies). The flush can be done synchronously
(-s) or asynchronously (-a).

ms See the msync command.

madvise [ -d | -r | -s | -w ] [ offset length ]
Modifies page cache behavior when operating on the current mapping. The range argu‐
ments are required by some advise commands ([*] below). With no arguments, the
POSIX_MADV_NORMAL advice is implied (default readahead).
-d the pages will not be needed (POSIX_MADV_DONTNEED[*]).
-r expect random page references (POSIX_MADV_RANDOM), which sets readahead to
zero.
-s expect sequential page references (POSIX_MADV_SEQUENTIAL), which doubles the
default readahead on the file.
-w advises the specified pages will be needed again (POSIX_MADV_WILLNEED[*]) which
forces the maximum readahead.

mincore
Dumps a list of pages or ranges of pages that are currently in core, for the current
memory mapping.

FILESYSTEM COMMANDS
bulkstat [ -a agno ] [ -d ] [ -e endino ] [ -n batchsize ] [ -s startino ] [ -v version"]
Display raw stat information about a bunch of inodes in an XFS filesystem. Options
are as follows:
-a agno
Display only results from the given allocation group. If not specified, all
results returned will be displayed.
-d Print debugging information about call results.
-e endino
Stop displaying records when this inode number is reached. Defaults to
stopping when the system call stops returning results.
-n batchsize
Retrieve at most this many records per call. Defaults to 4,096.
-s startino
Display inode allocation records starting with this inode. Defaults to the
first inode in the filesystem. If the given inode is not allocated, results
will begin with the next allocated inode in the filesystem.
-v version
Use a particular version of the kernel interface. Currently supported ver‐
sions are 1 and 5.

bulkstat_single [ -d ] [ -v version ] [ inum... | special... ]
Display raw stat information about individual inodes in an XFS filesystem. The -d and
-v options are the same as the bulkstat command. Arguments must be inode numbers or
any of the special values:
root Display information about the root directory inode.

freeze Suspend all write I/O requests to the filesystem of the current file. Only available
in expert mode and requires privileges.

thaw Undo the effects of a filesystem freeze operation. Only available in expert mode and
requires privileges.

inject [ tag ]
Inject errors into a filesystem to observe filesystem behavior at specific points un‐
der adverse conditions. Without the tag argument, displays the list of error tags
available. Only available in expert mode and requires privileges.

resblks [ blocks ]
Get and/or set count of reserved filesystem blocks using the XFS_IOC_GET_RESBLKS or
XFS_IOC_SET_RESBLKS system calls. Note -- this can be useful for exercising out of
space behavior. Only available in expert mode and requires privileges.

shutdown [ -f ]
Force the filesystem to shut down, preventing any further IO. XFS and other filesys‐
tems implement this functionality, although implementation details may differ
slightly. Only available in expert mode and requires privileges.

By default, the filesystem will not attempt to flush completed transactions to disk
before shutting down the filesystem. This simulates a disk failure or crash.
-f Force the filesystem to flush all completed transactions to disk before shut‐
ting down, matching XFS behavior when critical corruption is encountered.

statfs [ -c ] [ -g ] [ -s ]
Report selected statistics on the filesystem where the current file resides. The de‐
fault behavior is to enable all three reporting options:
-c Display XFS_IOC_FSCOUNTERS summary counter data.
-g Display XFS_IOC_FSGEOMETRY filesystem geometry data.
-s Display statfs(2) data.

inode [ [ -n ] number ] [ -v ]
The inode command queries physical information about an inode. With no arguments, it
will return 1 or 0, indicating whether or not any inode numbers greater than 32 bits
are currently in use in the filesystem. If given an inode number as an argument, the
command will return the same inode number if it is in use, or 0 if not. With -n number
, the next used inode number after this number will be returned, or zero if the sup‐
plied inode number is the highest one in use. With -v the command will also report the
number of bits (32 or 64) used by the inode number printed in the result; if no inode
number was specified on the command line, the maximum possible inode number in the
system will be printed along with its size.

inumbers [ -a agno ] [ -d ] [ -e endino ] [ -n batchsize ] [ -s startino ] [ -v version ]
Prints allocation information about groups of inodes in an XFS filesystem. Callers
can use this information to figure out which inodes are allocated. Options are as
follows:
-a agno
Display only results from the given allocation group. If not specified, all
results returned will be displayed.
-d Print debugging information about call results.
-e endino
Stop displaying records when this inode number is reached. Defaults to
stopping when the system call stops returning results.
-n batchsize
Retrieve at most this many records per call. Defaults to 4,096.
-s startino
Display inode allocation records starting with this inode. Defaults to the
first inode in the filesystem. If the given inode is not allocated, results
will begin with the next allocated inode in the filesystem.
-v version
Use a particular version of the kernel interface. Currently supported ver‐
sions are 1 and 5.

scrub type [ agnumber | ino gen ]
Scrub internal XFS filesystem metadata. The type parameter specifies which type of
metadata to scrub. For AG metadata, one AG number must be specified. For file meta‐
data, the scrub is applied to the open file unless the inode number and generation
number are specified.

repair type [ agnumber | ino gen ]
Repair internal XFS filesystem metadata. The type parameter specifies which type of
metadata to repair. For AG metadata, one AG number must be specified. For file meta‐
data, the repair is applied to the open file unless the inode number and generation
number are specified.

label [ -c | -s label ]
On filesystems that support online label manipulation, get, set, or clear the filesys‐
tem label. With no options, print the current filesystem label. The -c option clears
the filesystem label by setting it to the null string. The -s label option sets the
filesystem label to label. If the label is longer than the filesystem will accept,
xfs_io will print an error message. XFS filesystem labels can be at most 12 charac‐
ters long.

fsmap [ -d | -l | -r ] [ -m | -v ] [ -n nx ] [ start ] [ end ]
Prints the mapping of disk blocks used by the filesystem hosting the current file.
The map lists each extent used by files, allocation group metadata, journalling logs,
and static filesystem metadata, as well as any regions that are unused. Each line of
the listings takes the following form:

extent: major:minor [startblock..endblock]: owner startoffset..endoffset length

Static filesystem metadata, allocation group metadata, btrees, journalling logs, and
free space are marked by replacing the startoffset..endoffset with the appropriate
marker. All blocks, offsets, and lengths are specified in units of 512-byte blocks,
no matter what the filesystem's block size is. The optional start and end arguments
can be used to constrain the output to a particular range of disk blocks. If these
two options are specified, exactly one of -d, -l, or -r must also be set.
-d Display only extents from the data device. This option only applies for XFS
filesystems.
-l Display only extents from the external log device. This option only applies
to XFS filesystems.
-r Display only extents from the realtime device. This option only applies to
XFS filesystems.
-m Display results in a machine readable format (CSV). This option is not com‐
patible with the -v flag. The columns of the output are: extent number, de‐
vice major, device minor, physical start, physical end, owner, offset start,
offset end, length. The start, end, and length numbers are provided in
units of 512b. The owner field is a special string that takes the form:

inode_%lld_data
for inode data.
inode_%lld_data_bmbt
for inode data extent maps.
inode_%lld_attr
for inode extended attribute data.
inode_%lld_attr_bmbt
for inode extended attribute extent maps.
special_%u:%u
for other filesystem metadata.

-n num_extents
If this option is given, fsmap obtains the extent list of the file in groups
of num_extents extents. In the absence of -n, fsmap queries the system for
extents in groups of 131,072 records.

-v Shows verbose information. When this flag is specified, additional AG spe‐
cific information is appended to each line in the following form:

agno (startagblock..endagblock) nblocks flags

A second -v option will print out the flags legend. This option is not com‐
patible with the -m flag.

OTHER COMMANDS
help [ command ]
Display a brief description of one or all commands.

print Display a list of all open files and memory mapped regions. The current file and cur‐
rent mapping are distinguishable from any others.

p See the print command.

quit Exit xfs_io.

q See the quit command.

log_writes -d device -m mark
Create a mark named mark in the dm-log-writes log specified by device. This is in‐
tended to be equivalent to the shell command:

dmsetup message device 0 mark mark

lw See the log_writes command.

crc32cselftest
Test the internal crc32c implementation to make sure that it computes results cor‐
rectly.

SEE ALSO
mkfs.xfs(8), xfsctl(3), xfs_bmap(8), xfs_db(8), xfs(5), fdatasync(2), fstat(2), fstatfs(2),
fsync(2), ftruncate(2), futimens(3), mmap(2), msync(2), open(2), pread(2), pwrite(2), read‐‐
dir(3), dmsetup(8).

xfs_io(8)