{
    "mode": "man",
    "parameter": "xfs",
    "section": "5",
    "url": "https://www.chedong.com/phpMan.php/man/xfs/5/json",
    "generated": "2026-06-15T14:23:49Z",
    "sections": {
        "NAME": {
            "content": "xfs - layout, mount options, and supported file attributes for the XFS filesystem\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "An  XFS  filesystem  can  reside  on a regular disk partition or on a logical volume.  An XFS\nfilesystem has up to three parts: a data section, a log section, and a realtime section.  Us‐\ning the default mkfs.xfs(8) options, the realtime section is absent, and the log area is con‐\ntained within the data section.  The log section can be either separate from the data section\nor contained within it.  The filesystem sections are divided into a certain number of blocks,\nwhose size is specified at mkfs.xfs(8) time with the -b option.\n\nThe data section contains all the filesystem metadata (inodes, directories, indirect  blocks)\nas  well  as the user file data for ordinary (non-realtime) files and the log area if the log\nis internal to the data section.  The data section is divided into  a  number  of  allocation\ngroups.  The number and size of the allocation groups are chosen by mkfs.xfs(8) so that there\nis normally a small number of equal-sized groups.  The number of allocation  groups  controls\nthe  amount  of  parallelism  available in file and block allocation.  It should be increased\nfrom the default if there is sufficient memory and a lot of allocation activity.  The  number\nof  allocation  groups should not be set very high, since this can cause large amounts of CPU\ntime to be used by the filesystem, especially when the filesystem is nearly full.  More allo‐\ncation groups are added (of the original size) when xfsgrowfs(8) is run.\n\nThe  log section (or area, if it is internal to the data section) is used to store changes to\nfilesystem metadata while the filesystem is running until those changes are made to the  data\nsection.   It  is  written  sequentially  during normal operation and read only during mount.\nWhen mounting a filesystem after a crash, the log is read to complete operations that were in\nprogress at the time of the crash.\n\nThe  realtime section is used to store the data of realtime files.  These files had an attri‐\nbute bit set through xfsctl(3) after file creation, before any data was written to the  file.\nThe  realtime  section  is  divided  into  a  number  of  extents of fixed size (specified at\nmkfs.xfs(8) time).  Each file in the realtime section has an extent size that is  a  multiple\nof the realtime section extent size.\n\nEach  allocation  group  contains several data structures.  The first sector contains the su‐\nperblock.  For allocation groups after the first, the superblock is just a copy  and  is  not\nupdated  after  mkfs.xfs(8).   The next three sectors contain information for block and inode\nallocation within the allocation group.  Also contained within each allocation group are data\nstructures to locate free blocks and inodes; these are located through the header structures.\n\nEach XFS filesystem is labeled with a Universal Unique Identifier (UUID).  The UUID is stored\nin every allocation group header and is used to help distinguish one XFS filesystem from  an‐\nother,  therefore  you  should  avoid using dd(1) or other block-by-block copying programs to\ncopy XFS filesystems.  If two XFS filesystems on the same machine have the  same  UUID,  xfs‐‐\ndump(8)  may become confused when doing incremental and resumed dumps.  xfsdump(8) and xfsre‐‐\nstore(8) are recommended for making copies of XFS filesystems.\n",
            "subsections": []
        },
        "OPERATIONS": {
            "content": "Some functionality specific to the XFS filesystem is accessible to applications  through  the\nxfsctl(3) and by-handle (see openbyhandle(3)) interfaces.\n",
            "subsections": []
        },
        "MOUNT OPTIONS": {
            "content": "The  following  XFS-specific mount options may be used when mounting an XFS filesystem. Other\ngeneric options may be used as well; refer to the mount(8) manual page for more details.\n",
            "subsections": [
                {
                    "name": "allocsize=size",
                    "content": "Sets the buffered I/O end-of-file preallocation size  when  doing  delayed  allocation\nwriteout. Valid values for this option are page size (typically 4KiB) through to 1GiB,\ninclusive, in power-of-2 increments.\n\nThe default behavior is for dynamic end-of-file preallocation size, which uses  a  set\nof  heuristics to optimise the preallocation size based on the current allocation pat‐\nterns within the file and the access patterns to the file. Specifying a  fixed  alloc‐\nsize value turns off the dynamic behavior.\n\nattr2|noattr2\nNote:  These  options have been deprecated as of kernel v5.10; The noattr2 option will\nbe removed no earlier than in September 2025 and attr2 option will  be  immutable  de‐\nfault.\n\nThe options enable/disable an \"opportunistic\" improvement to be made in the way inline\nextended attributes are stored on-disk.  When the new form is used for the first  time\nwhen  attr2  is selected (either when setting or removing extended attributes) the on-\ndisk superblock feature bit field will be updated to reflect this format being in use.\n\nThe default behavior is determined by the on-disk feature bit  indicating  that  attr2\nbehavior  is  active. If either mount option it set, then that becomes the new default\nused by the filesystem.\n\nCRC enabled filesystems always use the attr2 format, and so will  reject  the  noattr2\nmount option if it is set.\n"
                },
                {
                    "name": "dax=value",
                    "content": "Set CPU direct access (DAX) behavior for the current filesystem. This mount option ac‐\ncepts the following values:\n\n\"dax=inode\" DAX will be enabled only on regular files with FSXFLAGDAX applied.\n\n\"dax=never\" DAX will not be enabled for any files. FSXFLAGDAX will be ignored.\n\n\"dax=always\" DAX will be enabled for all regular files, regardless of the FSXFLAGDAX\nstate.\n\nIf  no  option  is  used  when  mounting  a filesystem stored on a DAX capable device,\ndax=inode will be used as default.\n\nFor details regarding DAX behavior in kernel, please refer to  kernel's  documentation\nat filesystems/dax.txt\n\ndiscard|nodiscard\nEnable/disable  the issuing of commands to let the block device reclaim space freed by\nthe filesystem.  This is useful for SSD devices, thinly provisioned LUNs  and  virtual\nmachine images, but may have a performance impact.\n\nNote:  It  is currently recommended that you use the fstrim application to discard un‐\nused blocks rather than the discard mount option because  the  performance  impact  of\nthis option is quite severe.  For this reason, nodiscard is the default.\n\ngrpid|bsdgroups|nogrpid|sysvgroups\nThese  options  define what group ID a newly created file gets.  When grpid is set, it\ntakes the group ID of the directory in which it is created; otherwise it takes the fs‐\ngid of the current process, unless the directory has the setgid bit set, in which case\nit takes the gid from the parent directory, and also gets the setgid bit set if it  is\na directory itself.\n"
                },
                {
                    "name": "filestreams",
                    "content": "Make the data allocator use the filestreams allocation mode across the entire filesys‐\ntem rather than just on directories configured to use it.\n\nikeep|noikeep\nNote: These options have been deprecated as of kernel v5.10; The noikeep  option  will\nbe  removed  no  earlier than in September 2025 and ikeep option will be immutable de‐\nfault.\n\n\nWhen ikeep is specified, XFS does not delete  empty  inode  clusters  and  keeps  them\naround  on  disk.  When noikeep is specified, empty inode clusters are returned to the\nfree space pool.  noikeep is the default.\n\ninode32|inode64\nWhen inode32 is specified, it indicates that XFS limits inode  creation  to  locations\nwhich will not result in inode numbers with more than 32 bits of significance.\n\nWhen  inode64  is  specified, it indicates that XFS is allowed to create inodes at any\nlocation in the filesystem, including those which will result in inode numbers occupy‐\ning more than 32 bits of significance.\n\ninode32  is  provided for backwards compatibility with older systems and applications,\nsince 64 bits inode numbers might cause problems for  some  applications  that  cannot\nhandle large inode numbers.  If applications are in use which do not handle inode num‐\nbers bigger than 32 bits, the inode32 option should be specified.\n\nFor kernel v3.7 and later, inode64 is the default.\n\nlargeio|nolargeio\nIf \"nolargeio\" is specified, the optimal I/O reported in stblksize by stat(2) will be\nas small as possible to allow user applications to avoid inefficient read/modify/write\nI/O.  This is typically the page size of the machine, as this is  the  granularity  of\nthe page cache.\n\nIf  \"largeio\"  specified, a filesystem that was created with a \"swidth\" specified will\nreturn the \"swidth\" value (in bytes) in stblksize. If the filesystem does not have  a\n\"swidth\" specified but does specify an \"allocsize\" then \"allocsize\" (in bytes) will be\nreturned instead. Otherwise the behavior is the same as if \"nolargeio\" was  specified.\nnolargeio is the default.\n"
                },
                {
                    "name": "logbufs=value",
                    "content": "Set the number of in-memory log buffers.  Valid numbers range from 2–8 inclusive.\n\nThe default value is 8 buffers.\n\nIf  the  memory cost of 8 log buffers is too high on small systems, then it may be re‐\nduced at some cost to performance on metadata intensive workloads. The logbsize option\nbelow controls the size of each buffer and so is also relevant to this case.\n"
                },
                {
                    "name": "logbsize=value",
                    "content": "Set  the size of each in-memory log buffer.  The size may be specified in bytes, or in\nkibibytes (KiB) with a \"k\" suffix.  Valid sizes for version 1 and version 2  logs  are\n16384  (value=16k) and 32768 (value=32k).  Valid sizes for version 2 logs also include\n65536 (value=64k), 131072 (value=128k) and 262144 (value=256k). The logbsize  must  be\nan integer multiple of the log stripe unit configured at mkfs time.\n\nThe  default  value for version 1 logs is 32768, while the default value for version 2\nlogs is max(32768, logsunit).\n\nlogdev=device and rtdev=device\nUse an external log (metadata journal) and/or real-time device.  An XFS filesystem has\nup  to three parts: a data section, a log section, and a real-time section.  The real-\ntime section is optional, and the log section can be separate from the data section or\ncontained within it.\n"
                },
                {
                    "name": "noalign",
                    "content": "Data  allocations will not be aligned at stripe unit boundaries. This is only relevant\nto filesystems created with non-zero data  alignment  parameters  (sunit,  swidth)  by\nmkfs.\n"
                },
                {
                    "name": "norecovery",
                    "content": "The  filesystem  will  be mounted without running log recovery.  If the filesystem was\nnot cleanly unmounted, it is likely to be inconsistent when  mounted  in  \"norecovery\"\nmode.   Some  files or directories may not be accessible because of this.  Filesystems\nmounted \"norecovery\" must be mounted read-only or the mount will fail.\n\nnouuid Don't check for double mounted file systems using the file system uuid.  This is  use‐\nful to mount LVM snapshot volumes, and often used in combination with \"norecovery\" for\nmounting read-only snapshots.\n"
                },
                {
                    "name": "noquota",
                    "content": "Forcibly turns off all quota accounting and enforcement within the filesystem.\n"
                },
                {
                    "name": "uquota/usrquota/quota/uqnoenforce/qnoenforce",
                    "content": "User disk quota accounting  enabled,  and  limits  (optionally)  enforced.   Refer  to\nxfsquota(8) for further details.\n"
                },
                {
                    "name": "gquota/grpquota/gqnoenforce",
                    "content": "Group  disk  quota  accounting  enabled  and  limits  (optionally) enforced.  Refer to\nxfsquota(8) for further details.\n"
                },
                {
                    "name": "pquota/prjquota/pqnoenforce",
                    "content": "Project disk quota accounting enabled and  limits  (optionally)  enforced.   Refer  to\nxfsquota(8) for further details.\n\nsunit=value and swidth=value\nUsed  to  specify  the  stripe  unit  and  width for a RAID device or a stripe volume.\n\"value\" must be specified in 512-byte block units. These options are only relevant  to\nfilesystems that were created with non-zero data alignment parameters.\n\nThe  sunit  and  swidth  parameters  specified  must  be  compatible with the existing\nfilesystem alignment characteristics.  In general, that means the only  valid  changes\nto sunit are increasing it by a power-of-2 multiple. Valid swidth values are any inte‐\nger multiple of a valid sunit value.\n\nTypically the only time these mount options are necessary if after an underlying  RAID\ndevice  has  had  it's geometry modified, such as adding a new disk to a RAID5 lun and\nreshaping it.\n"
                },
                {
                    "name": "swalloc",
                    "content": "Data allocations will be rounded up to stripe width boundaries when the current end of\nfile is being extended and the file size is larger than the stripe width size.\n\nwsync  When  specified,  all filesystem namespace operations are executed synchronously. This\nensures that when the namespace operation (create, unlink, etc) completes, the  change\nto the namespace is on stable storage. This is useful in HA setups where failover must\nnot result in clients seeing inconsistent namespace presentation  during  or  after  a\nfailover event.\n"
                }
            ]
        },
        "REMOVED MOUNT OPTIONS": {
            "content": "The  following mount options have been removed from the kernel, and will yield mount failures\nif specified.  Mount options are deprecated for a significant period time prior to removal.\n\nName                        Removed\n----                        -------\ndelaylog/nodelaylog         v4.0\nihashsize                   v4.0\nirixsgid                    v4.0\nosyncisdsync/osyncisosync   v4.0\nbarrier/nobarrier           v4.19\n",
            "subsections": []
        },
        "FILE ATTRIBUTES": {
            "content": "The XFS filesystem supports setting the following file attributes on Linux systems using  the\nchattr(1) utility:\n\na - append only\n\nA - no atime updates\n\nd - no dump\n\ni - immutable\n\nS - synchronous updates\n\nFor descriptions of these attribute flags, please refer to the chattr(1) man page.\n",
            "subsections": []
        },
        "SEE ALSO": {
            "content": "chattr(1),  xfsctl(3),  mount(8),  mkfs.xfs(8), xfsinfo(8), xfsadmin(8), xfsdump(8), xfsre‐‐\nstore(8).\n\n\n\nxfs(5)",
            "subsections": []
        }
    },
    "summary": "xfs - layout, mount options, and supported file attributes for the XFS filesystem",
    "flags": [],
    "examples": [],
    "see_also": [
        {
            "name": "chattr",
            "section": "1",
            "url": "https://www.chedong.com/phpMan.php/man/chattr/1/json"
        },
        {
            "name": "xfsctl",
            "section": "3",
            "url": "https://www.chedong.com/phpMan.php/man/xfsctl/3/json"
        },
        {
            "name": "mount",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/mount/8/json"
        },
        {
            "name": "mkfs.xfs",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/mkfs.xfs/8/json"
        },
        {
            "name": "xfsinfo",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/xfsinfo/8/json"
        },
        {
            "name": "xfsadmin",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/xfsadmin/8/json"
        },
        {
            "name": "xfsdump",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/xfsdump/8/json"
        },
        {
            "name": "store",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/store/8/json"
        }
    ]
}