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263 lines
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263 lines
11 KiB
Plaintext
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The SGI XFS Filesystem
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======================
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XFS is a high performance journaling filesystem which originated
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on the SGI IRIX platform. It is completely multi-threaded, can
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support large files and large filesystems, extended attributes,
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variable block sizes, is extent based, and makes extensive use of
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Btrees (directories, extents, free space) to aid both performance
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and scalability.
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Refer to the documentation at http://oss.sgi.com/projects/xfs/
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for further details. This implementation is on-disk compatible
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with the IRIX version of XFS.
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Mount Options
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=============
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When mounting an XFS filesystem, the following options are accepted.
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allocsize=size
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Sets the buffered I/O end-of-file preallocation size when
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doing delayed allocation writeout (default size is 64KiB).
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Valid values for this option are page size (typically 4KiB)
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through to 1GiB, inclusive, in power-of-2 increments.
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attr2/noattr2
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The options enable/disable (default is disabled for backward
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compatibility on-disk) an "opportunistic" improvement to be
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made in the way inline extended attributes are stored on-disk.
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When the new form is used for the first time (by setting or
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removing extended attributes) the on-disk superblock feature
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bit field will be updated to reflect this format being in use.
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barrier
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Enables the use of block layer write barriers for writes into
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the journal and unwritten extent conversion. This allows for
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drive level write caching to be enabled, for devices that
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support write barriers.
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dmapi
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Enable the DMAPI (Data Management API) event callouts.
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Use with the "mtpt" option.
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grpid/bsdgroups and nogrpid/sysvgroups
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These options define what group ID a newly created file gets.
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When grpid is set, it takes the group ID of the directory in
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which it is created; otherwise (the default) it takes the fsgid
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of the current process, unless the directory has the setgid bit
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set, in which case it takes the gid from the parent directory,
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and also gets the setgid bit set if it is a directory itself.
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ihashsize=value
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Sets the number of hash buckets available for hashing the
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in-memory inodes of the specified mount point. If a value
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of zero is used, the value selected by the default algorithm
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will be displayed in /proc/mounts.
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ikeep/noikeep
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When inode clusters are emptied of inodes, keep them around
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on the disk (ikeep) - this is the traditional XFS behaviour
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and is still the default for now. Using the noikeep option,
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inode clusters are returned to the free space pool.
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inode64
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Indicates that XFS is allowed to create inodes at any location
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in the filesystem, including those which will result in inode
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numbers occupying more than 32 bits of significance. This is
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provided for backwards compatibility, but causes problems for
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backup applications that cannot handle large inode numbers.
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largeio/nolargeio
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If "nolargeio" is specified, the optimal I/O reported in
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st_blksize by stat(2) will be as small as possible to allow user
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applications to avoid inefficient read/modify/write I/O.
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If "largeio" specified, a filesystem that has a "swidth" specified
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will return the "swidth" value (in bytes) in st_blksize. If the
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filesystem does not have a "swidth" specified but does specify
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an "allocsize" then "allocsize" (in bytes) will be returned
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instead.
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If neither of these two options are specified, then filesystem
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will behave as if "nolargeio" was specified.
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logbufs=value
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Set the number of in-memory log buffers. Valid numbers range
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from 2-8 inclusive.
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The default value is 8 buffers for filesystems with a
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blocksize of 64KiB, 4 buffers for filesystems with a blocksize
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of 32KiB, 3 buffers for filesystems with a blocksize of 16KiB
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and 2 buffers for all other configurations. Increasing the
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number of buffers may increase performance on some workloads
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at the cost of the memory used for the additional log buffers
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and their associated control structures.
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logbsize=value
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Set the size of each in-memory log buffer.
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Size may be specified in bytes, or in kilobytes with a "k" suffix.
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Valid sizes for version 1 and version 2 logs are 16384 (16k) and
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32768 (32k). Valid sizes for version 2 logs also include
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65536 (64k), 131072 (128k) and 262144 (256k).
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The default value for machines with more than 32MiB of memory
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is 32768, machines with less memory use 16384 by default.
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logdev=device and rtdev=device
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Use an external log (metadata journal) and/or real-time device.
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An XFS filesystem has up to three parts: a data section, a log
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section, and a real-time section. The real-time section is
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optional, and the log section can be separate from the data
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section or contained within it.
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mtpt=mountpoint
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Use with the "dmapi" option. The value specified here will be
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included in the DMAPI mount event, and should be the path of
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the actual mountpoint that is used.
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noalign
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Data allocations will not be aligned at stripe unit boundaries.
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noatime
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Access timestamps are not updated when a file is read.
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norecovery
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The filesystem will be mounted without running log recovery.
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If the filesystem was not cleanly unmounted, it is likely to
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be inconsistent when mounted in "norecovery" mode.
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Some files or directories may not be accessible because of this.
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Filesystems mounted "norecovery" must be mounted read-only or
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the mount will fail.
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nouuid
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Don't check for double mounted file systems using the file system uuid.
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This is useful to mount LVM snapshot volumes.
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osyncisosync
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Make O_SYNC writes implement true O_SYNC. WITHOUT this option,
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Linux XFS behaves as if an "osyncisdsync" option is used,
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which will make writes to files opened with the O_SYNC flag set
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behave as if the O_DSYNC flag had been used instead.
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This can result in better performance without compromising
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data safety.
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However if this option is not in effect, timestamp updates from
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O_SYNC writes can be lost if the system crashes.
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If timestamp updates are critical, use the osyncisosync option.
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uquota/usrquota/uqnoenforce/quota
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User disk quota accounting enabled, and limits (optionally)
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enforced. Refer to xfs_quota(8) for further details.
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gquota/grpquota/gqnoenforce
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Group disk quota accounting enabled and limits (optionally)
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enforced. Refer to xfs_quota(8) for further details.
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pquota/prjquota/pqnoenforce
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Project disk quota accounting enabled and limits (optionally)
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enforced. Refer to xfs_quota(8) for further details.
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sunit=value and swidth=value
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Used to specify the stripe unit and width for a RAID device or
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a stripe volume. "value" must be specified in 512-byte block
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units.
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If this option is not specified and the filesystem was made on
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a stripe volume or the stripe width or unit were specified for
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the RAID device at mkfs time, then the mount system call will
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restore the value from the superblock. For filesystems that
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are made directly on RAID devices, these options can be used
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to override the information in the superblock if the underlying
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disk layout changes after the filesystem has been created.
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The "swidth" option is required if the "sunit" option has been
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specified, and must be a multiple of the "sunit" value.
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swalloc
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Data allocations will be rounded up to stripe width boundaries
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when the current end of file is being extended and the file
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size is larger than the stripe width size.
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sysctls
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=======
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The following sysctls are available for the XFS filesystem:
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fs.xfs.stats_clear (Min: 0 Default: 0 Max: 1)
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Setting this to "1" clears accumulated XFS statistics
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in /proc/fs/xfs/stat. It then immediately resets to "0".
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fs.xfs.xfssyncd_centisecs (Min: 100 Default: 3000 Max: 720000)
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The interval at which the xfssyncd thread flushes metadata
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out to disk. This thread will flush log activity out, and
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do some processing on unlinked inodes.
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fs.xfs.xfsbufd_centisecs (Min: 50 Default: 100 Max: 3000)
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The interval at which xfsbufd scans the dirty metadata buffers list.
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fs.xfs.age_buffer_centisecs (Min: 100 Default: 1500 Max: 720000)
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The age at which xfsbufd flushes dirty metadata buffers to disk.
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fs.xfs.error_level (Min: 0 Default: 3 Max: 11)
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A volume knob for error reporting when internal errors occur.
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This will generate detailed messages & backtraces for filesystem
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shutdowns, for example. Current threshold values are:
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XFS_ERRLEVEL_OFF: 0
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XFS_ERRLEVEL_LOW: 1
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XFS_ERRLEVEL_HIGH: 5
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fs.xfs.panic_mask (Min: 0 Default: 0 Max: 127)
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Causes certain error conditions to call BUG(). Value is a bitmask;
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AND together the tags which represent errors which should cause panics:
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XFS_NO_PTAG 0
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XFS_PTAG_IFLUSH 0x00000001
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XFS_PTAG_LOGRES 0x00000002
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XFS_PTAG_AILDELETE 0x00000004
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XFS_PTAG_ERROR_REPORT 0x00000008
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XFS_PTAG_SHUTDOWN_CORRUPT 0x00000010
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XFS_PTAG_SHUTDOWN_IOERROR 0x00000020
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XFS_PTAG_SHUTDOWN_LOGERROR 0x00000040
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This option is intended for debugging only.
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fs.xfs.irix_symlink_mode (Min: 0 Default: 0 Max: 1)
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Controls whether symlinks are created with mode 0777 (default)
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or whether their mode is affected by the umask (irix mode).
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fs.xfs.irix_sgid_inherit (Min: 0 Default: 0 Max: 1)
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Controls files created in SGID directories.
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If the group ID of the new file does not match the effective group
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ID or one of the supplementary group IDs of the parent dir, the
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ISGID bit is cleared if the irix_sgid_inherit compatibility sysctl
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is set.
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fs.xfs.restrict_chown (Min: 0 Default: 1 Max: 1)
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Controls whether unprivileged users can use chown to "give away"
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a file to another user.
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fs.xfs.inherit_sync (Min: 0 Default: 1 Max: 1)
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Setting this to "1" will cause the "sync" flag set
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by the xfs_io(8) chattr command on a directory to be
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inherited by files in that directory.
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fs.xfs.inherit_nodump (Min: 0 Default: 1 Max: 1)
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Setting this to "1" will cause the "nodump" flag set
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by the xfs_io(8) chattr command on a directory to be
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inherited by files in that directory.
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fs.xfs.inherit_noatime (Min: 0 Default: 1 Max: 1)
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Setting this to "1" will cause the "noatime" flag set
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by the xfs_io(8) chattr command on a directory to be
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inherited by files in that directory.
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fs.xfs.inherit_nosymlinks (Min: 0 Default: 1 Max: 1)
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Setting this to "1" will cause the "nosymlinks" flag set
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by the xfs_io(8) chattr command on a directory to be
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inherited by files in that directory.
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fs.xfs.rotorstep (Min: 1 Default: 1 Max: 256)
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In "inode32" allocation mode, this option determines how many
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files the allocator attempts to allocate in the same allocation
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group before moving to the next allocation group. The intent
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is to control the rate at which the allocator moves between
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allocation groups when allocating extents for new files.
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