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 cur-
rent open file, whilst commands run from the command line may be re-
peated 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 ex-
its 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. Mul-
tiple -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 privi-
leges.
-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 prealloca-
tion, 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 struc-
tures 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 command.
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 in-
stead. Without any arguments, displays statistics about the cur-
rent 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 in-
compatible with other flags specifying other O_xxx flags
apart from -L.
-L doesn't follow symlinks (O_NOFOLLOW). This is incompati-
ble 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 cur-
rent (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 op-
tion will set the file permissions to read-write (0644). This al-
lows 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 ] [ -qAdDwNOW ] [ -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.
-A Perform the pwritev2(2) call with RWF_ATOMIC.
-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 allo-
cating space for the currently open file. If the -R option is
specified, a recursive descent is performed for all directory en-
tries below the currently open file (-D can be used to restrict
the output to directories only). If the target file is a direc-
tory, 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 re-
ported 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 di-
rectory 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.
These commands are no longer supported as of Linux 5.17.
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 sys-
tem 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_SE-
QUENTIAL), which doubles the default readahead on the
file.
-w advises the specified data will be needed again
(POSIX_FADV_WILLNEED[*]) which forces the maximum reada-
head.
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_UN-
RESVSP 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 fal-
locate(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 elimi-
nates 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 fallo-
cate(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 ftrun-
cate(2).
sendfile [ -q ] -i srcfile | -f N [ offset length ]
On platforms which support it, allows a direct in-kernel copy be-
tween 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 direc-
tory.
-v verbose mode - dump dirent content as defined in read-
dir(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 speci-
fied 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_off-
set in the open file to the same physical blocks that are mapped
at offset src_offset in the file src_file , replacing any con-
tents 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 af-
fected 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)).
exchangerange [OPTIONS]donor_file
Exchanges contents 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)). Op-
tions include:
-C Print timing information in a condensed format.
-c Exchange contents only if file2 has not changed.
-d dest_offset
Swap extents with open file beginning at dest_offset.
-f Flush changed file data and file metadata to disk.
-l length
Swap up to length bytes of data.
-n Perform all the parameter validation checks but don't
change anything.
-s src_offset
Swap extents with donor file beginning at src_offset.
-t Print timing information.
-w Only exchange written ranges in the supplied file.
set_encpolicy [ -c mode ] [ -n mode ] [ -f flags ] [ -s log2_dusize ] [
-v version ] [ keyspec ]
On filesystems that support encryption, assign an encryption pol-
icy 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 unspec-
ified, 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)
-s log2_dusize
log2 of data unit size. Not supported by v1 policies.
-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 encryp-
tion policies that use this descriptor. Otherwise, the
key is added as a v2 policy key, and on success the re-
sulting "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 di-
rectory 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 re-
fer 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 name-
space.
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_BA-
SIC_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 set-
ting 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 [ -fpz ] [ -b bufsize ] [ -i ino ] [ -n name ] [ ino gen ]
By default this command prints out the parent inode numbers, in-
ode generation numbers and basenames of all the hardlinks which
point to the inode of the current file.
If the optional ino and gen parameters are provided, they will be
used to create a file handle on the same filesystem as the open
file. The parents of the file represented by the handle will be
reported instead of the open file.
-b Use a buffer of this size to receive parent pointer
records from the kernel.
-i Only show parent pointer records containing this inode
number.
-n Only show parent pointer records containing this directory
entry name.
-p the output is similar to the default output except path-
names up to the mount-point are printed out instead of the
component name.
-s Print records in short format: ino/gen/namelen/name
-z Print only the first path from the root.
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.
startupdate [ -e]
Create a temporary clone of a file in which to stage file up-
dates. The -e option creates an empty staging file.
cancelupdate
Abandon changes from a update staging file.
commitupdate [OPTIONS]
Commit changes from a update staging file to the real file.
-C Print timing information in a condensed format.
-h Only swap ranges in the update staging file that were ac-
tually written.
-k Do not change file size.
-n Check parameters without changing anything.
-q Do not print timing information at all.
MEMORY MAPPED I/O COMMANDS
mmap [ N | [[ -rwxS ] [-s size ] offset length ]]
With no arguments, mmap shows the current mappings. Specifying a
single numeric argument N sets the current mapping. If two argu-
ments 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 re-
serve 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 map-
ping 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 standard 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 de-
fault stored value is 'X', repeated to fill the range specified,
but this can be changed using the -S option. 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 stor-
age 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 map-
ping. The range arguments 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 reada-
head.
mincore
Dumps a list of pages or ranges of pages that are currently in
core, for the current memory mapping.
FILESYSTEM COMMANDS
aginfo [ -a agno ]
Show information about or update the state of allocation groups.
-a Act only on a specific allocation group.
bulkstat [ -a agno ] [ -d ] [ -e endino ] [ -m ] [ -n batchsize ] [ -q ]
[ -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 dis-
played.
-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.
-m Include metadata directories in the output.
-n batchsize
Retrieve at most this many records per call. Defaults
to 4,096.
-q Run quietly. Does not parse or output retrieved bulk-
stat information.
-s startino
Display inode allocation records starting with this in-
ode. 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. Cur-
rently supported versions are 1 and 5.
bulkstat_single [ -d ] [ -m ] [ -v version ] [ inum... | special... ]
Display raw stat information about individual inodes in an XFS
filesystem. The -d, -m, and -v options are the same as the bulk-
stat command. Arguments must be inode numbers or any of the spe-
cial 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 avail-
able in expert mode and requires privileges.
inject [ tag ]
Inject errors into a filesystem to observe filesystem behavior at
specific points under adverse conditions. Without the tag argu-
ment, displays the list of error tags available. Only available
in expert mode and requires privileges.
rginfo [ -r rgno ]
Show information about or update the state of realtime allocation
groups.
-r Act only on a specific realtime group.
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 filesystems 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 shutting 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 default behavior is to enable all three re-
porting 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 supplied 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 dis-
played.
-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 in-
ode. 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. Cur-
rently supported versions are 1 and 5.
scrub type [ agnumber | rgnumber | ino gen | metapath [ rgnumber ] ]
Scrub internal XFS filesystem metadata. The type parameter spec-
ifies which type of metadata to scrub. For AG metadata, one AG
number must be specified. For realtime group metadata, one rt-
group number must be specified. For file metadata, the scrub is
applied to the open file unless the inode number and generation
number are specified. For metapath, the name of a file or a raw
number must be specified. If the metapath file is a per-rtgroup
file, the group number must be specified.
scrubv [ -b NN ] [ -d ] [ -m oflags ] [ -r ] [ -v NN ] [ -w ms ] group [
agnumber | ino gen ]
Scrub a bunch of internal XFS filesystem metadata. The group pa-
rameter specifies which group of metadata to scrub. Valid groups
are ag, agheader, inode, iscan, fs, probe, rtgroup, or summary.
For ag and agheader metadata, one AG number must be specified.
For inode metadata, the scrub is applied to the open file unless
the inode number and generation number are specified. For rt-
group metadata, one rt group number must be specified.
-b NN Inject scrub barriers into the vector stream at the
given interval. Barriers abort vector processing if
any previous scrub function found corruption.
-d Enables debug mode.
-m Fail scrub barriers if any of these scrub output flags
are seen.
-r Repair metadata if corruptions are found. This option
requires expert mode.
-v NN Force a particular API version. single selects
XFS_SCRUB_METADATA (one-by-one). vector selects
XFS_SCRUBV_METADATA (vectored). If no option is speci-
fied, vector mode will be used, with a fallback to sin-
gle mode if the kernel doesn't recognize the vector
mode ioctl.
-w us Wait the given number of microseconds between each
scrub function.
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 metadata, the repair is
applied to the open file unless the inode number and generation
number are specified. The -R option can be specified to force
rebuilding of a metadata structure.
label [ -c | -s label ]
On filesystems that support online label manipulation, get, set,
or clear the filesystem label. With no options, print the cur-
rent 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 characters 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, allo-
cation 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 startoff-
set..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 speci-
fied, 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 compatible with the -v flag. The
columns of the output are: extent number, device major,
device minor, physical start, physical end, owner, off-
set 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 speci-
fied, additional AG specific 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 compatible with the -m flag.
fsuuid Print the mounted filesystem UUID.
sysfspath
Print the sysfs or debugfs path for the mounted filesystem.
The -d option selects debugfs instead of sysfs.
getfsprops name [ names... ]
Retrieve the values of the given filesystem properties.
listfsprops [ -v ]
List all filesystem properties that have been stored in the
filesystem. If the -v flag is specified, prints the values of
the properties.
setfsprops name=value [ name=value... ]
Set the given filesystem properties to the specified values.
removefsprops name [ names... ]
Remove the given filesystem properties.
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 current 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 intended 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 com-
putes results correctly.
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), readdir(3), dmsetup(8).
xfs_io(8)
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