xfs_db(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | CONCEPTS | COMMANDS | TYPES | DIAGNOSTICS | SEE ALSO | COLOPHON

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

NAME         top

       xfs_db - debug an XFS filesystem

SYNOPSIS         top

       xfs_db [ -c cmd ] ... [ -i|r|x|F ] [ -f ] [ -l logdev ] [ -p
       progname ] device
       xfs_db -V

DESCRIPTION         top

       xfs_db is used to examine an XFS filesystem. Under rare
       circumstances it can also be used to modify an XFS filesystem,
       but that task is normally left to xfs_repair(8) or to scripts
       such as xfs_admin(8) that run xfs_db.

OPTIONS         top

       -c cmd xfs_db commands may be run interactively (the default) or
              as arguments on the command line. Multiple -c arguments
              may be given. The commands are run in the sequence given,
              then the program exits.

       -f     Specifies that the filesystem image to be processed is
              stored in a regular file at device (see the mkfs.xfs(8) -d
              file option).  This might happen if an image copy of a
              filesystem has been made into an ordinary file with
              xfs_copy(8).

       -F     Specifies that we want to continue even if the superblock
              magic is not correct.  For use in xfs_metadump.

       -i     Allows execution on a mounted filesystem, provided it is
              mounted read-only.  Useful for shell scripts which must
              only operate on filesystems in a guaranteed consistent
              state (either unmounted or mounted read-only). These
              semantics are slightly different to that of the -r option.

       -l logdev
              Specifies the device where the filesystems external log
              resides.  Only for those filesystems which use an external
              log. See the mkfs.xfs(8) -l option, and refer to xfs(5)
              for a detailed description of the XFS log.

       -p progname
              Set the program name to progname for prompts and some
              error messages, the default value is xfs_db.

       -r     Open device or filename read-only. This option is required
              if the filesystem is mounted.  It is only necessary to
              omit this flag if a command that changes data (write,
              blocktrash, crc) is to be used.

       -x     Specifies expert mode.  This enables the (write,
              blocktrash, crc invalidate/revalidate) commands.

       -V     Prints the version number and exits.

CONCEPTS         top

       xfs_db commands can be broken up into two classes. Most commands
       are for the navigation and display of data structures in the
       filesystem.  Other commands are for scanning the filesystem in
       some way.

       Commands which are used to navigate the filesystem structure take
       arguments which reflect the names of filesystem structure fields.
       There can be multiple field names separated by dots when the
       underlying structures are nested, as in C.  The field names can
       be indexed (as an array index) if the underlying field is an
       array.  The array indices can be specified as a range, two
       numbers separated by a dash.

       xfs_db maintains a current address in the filesystem.  The
       granularity of the address is a filesystem structure.  This can
       be a filesystem block, an inode or quota (smaller than a
       filesystem block), or a directory block (could be larger than a
       filesystem block).  There are a variety of commands to set the
       current address.  Associated with the current address is the
       current data type, which is the structural type of this data.
       Commands which follow the structure of the filesystem always set
       the type as well as the address.  Commands which examine pieces
       of an individual file (inode) need the current inode to be set,
       this is done with the inode command.

       The current address/type information is actually maintained in a
       stack that can be explicitly manipulated with the push, pop, and
       stack commands.  This allows for easy examination of a nested
       filesystem structure.  Also, the last several locations visited
       are stored in a ring buffer which can be manipulated with the
       forward, back, and ring commands.

       XFS filesystems are divided into a small number of allocation
       groups.  xfs_db maintains a notion of the current allocation
       group which is manipulated by some commands. The initial
       allocation group is 0.

COMMANDS         top

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

       a      See the addr command.

       ablock filoff
              Set current address to the offset filoff (a filesystem
              block number) in the attribute area of the current inode.

       addr [field-expression]
              Set current address to the value of the field-expression.
              This is used to "follow" a reference in one structure to
              the object being referred to. If no argument is given, the
              current address is printed.

       agf [agno]
              Set current address to the AGF block for allocation group
              agno.  If no argument is given, use the current allocation
              group.

       agfl [agno]
              Set current address to the AGFL block for allocation group
              agno.  If no argument is given, use the current allocation
              group.

       agi [agno]
              Set current address to the AGI block for allocation group
              agno.  If no argument is given, use the current allocation
              group.

       agresv [agno]
              Displays the length, free block count, per-AG reservation
              size, and per-AG reservation usage for a given AG.  If no
              argument is given, display information for all AGs.

       attr_remove [-r|-u|-s] [-n] name
              Remove the specified extended attribute from the current
              file.

                 -r  Sets the attribute in the root namespace.  Only one
                     namespace option can be specified.

                 -u  Sets the attribute in the user namespace.  Only one
                     namespace option can be specified.

                 -s  Sets the attribute in the secure namespace.  Only
                     one namespace option can be specified.

                 -n  Do not enable 'noattr2' mode on V4 filesystems.

       attr_set [-r|-u|-s] [-n] [-R|-C] [-v namelen] name
              Sets an extended attribute on the current file with the
              given name.

                 -r  Sets the attribute in the root namespace.  Only one
                     namespace option can be specified.

                 -u  Sets the attribute in the user namespace.  Only one
                     namespace option can be specified.

                 -s  Sets the attribute in the secure namespace.  Only
                     one namespace option can be specified.

                 -n  Do not enable 'noattr2' mode on V4 filesystems.

                 -R  Replace the attribute.  The command will fail if
                     the attribute does not already exist.

                 -C  Create the attribute.  The command will fail if the
                     attribute already exists.

                 -v  Set the attribute value to a string of this length
                     containing the letter 'v'.

       b      See the back command.

       back   Move to the previous location in the position ring.

       blockfree
              Free block usage information collected by the last
              execution of the blockget command. This must be done
              before another blockget command can be given, presumably
              with different arguments than the previous one.

       blockget [-npvs] [-b bno] ... [-i ino] ...
              Get block usage and check filesystem consistency.  The
              information is saved for use by a subsequent blockuse,
              ncheck, or blocktrash command.

                 -b  is used to specify filesystem block numbers about
                     which verbose information should be printed.

                 -i  is used to specify inode numbers about which
                     verbose information should be printed.

                 -n  is used to save pathnames for inodes visited, this
                     is used to support the xfs_ncheck(8) command. It
                     also means that pathnames will be printed for
                     inodes that have problems. This option uses a lot
                     of memory so is not enabled by default.

                 -p  causes error messages to be prefixed with the
                     filesystem name being processed. This is useful if
                     several copies of xfs_db are run in parallel.

                 -s  restricts output to severe errors only. This is
                     useful if the output is too long otherwise.

                 -v  enables verbose output. Messages will be printed
                     for every block and inode processed.

       blocktrash [-z] [-o offset] [-n count] [-x min] [-y max] [-s
       seed] [-0|1|2|3] [-t type] ...
              Trash randomly selected filesystem metadata blocks.
              Trashing occurs to randomly selected bits in the chosen
              blocks.  This command is available only in debugging
              versions of xfs_db.  It is useful for testing
              xfs_repair(8).

                 -0 | -1 | -2 | -3
                     These are used to set the operating mode for
                     blocktrash.  Only one can be used: -0 changed bits
                     are cleared; -1 changed bits are set; -2 changed
                     bits are inverted; -3 changed bits are randomized.

                 -n  supplies the count of block-trashings to perform
                     (default 1).

                 -o  supplies the bit offset at which to start trashing
                     the block.  If the value is preceded by a '+', the
                     trashing will start at a randomly chosen offset
                     that is larger than the value supplied.  The
                     default is to randomly choose an offset anywhere in
                     the block.

                 -s  supplies a seed to the random processing.

                 -t  gives a type of blocks to be selected for trashing.
                     Multiple -t options may be given. If no -t options
                     are given then all metadata types can be trashed.

                 -x  sets the minimum size of bit range to be trashed.
                     The default value is 1.

                 -y  sets the maximum size of bit range to be trashed.
                     The default value is 1024.

                 -z  trashes the block at the top of the stack.  It is
                     not necessary to run blockget if this option is
                     supplied.

       blockuse [-n] [-c count]
              Print usage for current filesystem block(s).  For each
              block, the type and (if any) inode are printed.

                 -c  specifies a count of blocks to process. The default
                     value is 1 (the current block only).

                 -n  specifies that file names should be printed. The
                     prior blockget command must have also specified the
                     -n option.

       bmap [-a] [-d] [block [len]]
              Show the block map for the current inode.  The map display
              can be restricted to an area of the file with the block
              and len arguments. If block is given and len is omitted
              then 1 is assumed for len.

              The -a and -d options are used to select the attribute or
              data area of the inode, if neither option is given then
              both areas are shown.

       btdump [-a] [-i]
              If the cursor points to a btree node, dump the btree from
              that block downward.  If instead the cursor points to an
              inode, dump the data fork block mapping btree if there is
              one.  If the cursor points to a directory or extended
              attribute btree node, dump that.  By default, only records
              stored in the btree are dumped.

                 -a  If the cursor points at an inode, dump the extended
                     attribute block mapping btree, if present.

                 -i  Dump all keys and pointers in intermediate btree
                     nodes, and all records in leaf btree nodes.

       btheight [-b blksz] [-n recs] [-w max|-w min] btree types...
              For a given number of btree records and a btree type,
              report the number of records and blocks for each level of
              the btree, and the total number of blocks.  The btree type
              must be given after the options.

              A raw btree geometry can be provided in the format
              "record_bytes:key_bytes:ptr_bytes:header_type", where
              header_type is one of "short", "long", "shortcrc", or
              "longcrc".

              The supported btree types are: bnobt, cntbt, inobt,
              finobt, bmapbt, refcountbt, and rmapbt.

              Options are as follows:

                 -b  is used to override the btree block size.  The
                     default is the filesystem block size.

                 -n  is used to specify the number of records to store.
                     This argument is required.

                 -w max
                     shows only the best case scenario, which is when
                     the btree blocks are maximally loaded.

                 -w min
                     shows only the worst case scenario, which is when
                     the btree blocks are half full.

       check  See the blockget command.

       convert type number [type number] ... type
              Convert from one address form to another.  The known
              types, with alternate names, are:
                 agblock or agbno (filesystem block within an allocation
                        group)
                 agino or aginode (inode number within an allocation
                        group)
                 agnumber or agno (allocation group number)
                 bboff or daddroff (byte offset in a daddr)
                 blkoff or fsboff or agboff (byte offset in a agblock or
                        fsblock)
                 byte or fsbyte (byte address in filesystem)
                 daddr or bb (disk address, 512-byte blocks)
                 fsblock or fsb or fsbno (filesystem block, see the
                        fsblock command)
                 ino or inode (inode number)
                 inoidx or offset (index of inode in filesystem block)
                 inooff or inodeoff (byte offset in inode)

              Only conversions that "make sense" are allowed.  The
              compound form (with more than three arguments) is useful
              for conversions such as convert agno ag agbno agb fsblock.

       crc [-i|-r|-v]
              Invalidates, revalidates, or validates the CRC (checksum)
              field of the current structure, if it has one.  This
              command is available only on CRC-enabled filesystems.
              With no argument, validation is performed.  Each command
              will display the resulting CRC value and state.

                 -i  Invalidate the structure's CRC value (incrementing
                     it by one), and write it to disk.

                 -r  Recalculate the current structure's correct CRC
                     value, and write it to disk.

                 -v  Validate and display the current value and state of
                     the structure's CRC.

       daddr [d]
              Set current address to the daddr (512 byte block) given by
              d.  If no value for d is given, the current address is
              printed, expressed as a daddr.  The type is set to data
              (uninterpreted).

       dblock filoff
              Set current address to the offset filoff (a filesystem
              block number) in the data area of the current inode.

       debug [flagbits]
              Set debug option bits. These are used for debugging
              xfs_db.  If no value is given for flagbits, print the
              current debug option bits. These are for the use of the
              implementor.

       dquot [-g|-p|-u] id
              Set current address to a group, project or user quota
              block for the given ID. Defaults to user quota.

       echo [arg] ...
              Echo the arguments to the output.

       f      See the forward command.

       forward
              Move forward to the next entry in the position ring.

       frag [-adflqRrv]
              Get file fragmentation data. This prints information about
              fragmentation of file data in the filesystem (as opposed
              to fragmentation of freespace, for which see the freesp
              command). Every file in the filesystem is examined to see
              how far from ideal its extent mappings are. A summary is
              printed giving the totals.

                 -v  sets verbosity, every inode has information printed
                     for it.  The remaining options select which inodes
                     and extents are examined.  If no options are given
                     then all are assumed set, otherwise just those
                     given are enabled.

                 -a  enables processing of attribute data.

                 -d  enables processing of directory data.

                 -f  enables processing of regular file data.

                 -l  enables processing of symbolic link data.

                 -q  enables processing of quota file data.

                 -R  enables processing of realtime control file data.

                 -r  enables processing of realtime file data.

       freesp [-bcds] [-A alignment] [-a ag] ... [-e i] [-h h1] ... [-m
       m]
              Summarize free space for the filesystem. The free blocks
              are examined and totalled, and displayed in the form of a
              histogram, with a count of extents in each range of free
              extent sizes.

                 -A  reports only free extents with starting blocks
                     aligned to alignment blocks.

                 -a  adds ag to the list of allocation groups to be
                     processed. If no -a options are given then all
                     allocation groups are processed.

                 -b  specifies that the histogram buckets are binary-
                     sized, with the starting sizes being the powers of
                     2.

                 -c  specifies that freesp will search the by-size (cnt)
                     space Btree instead of the default by-block (bno)
                     space Btree.

                 -d  specifies that every free extent will be displayed.

                 -e  specifies that the histogram buckets are equal-
                     sized, with the size specified as i.

                 -h  specifies a starting block number for a histogram
                     bucket as h1.  Multiple -h's are given to specify
                     the complete set of buckets.

                 -m  specifies that the histogram starting block numbers
                     are powers of m.  This is the general case of -b.

                 -s  specifies that a final summary of total free
                     extents, free blocks, and the average free extent
                     size is printed.

       fsb    See the fsblock command.

       fsblock [fsb]
              Set current address to the fsblock value given by fsb.  If
              no value for fsb is given the current address is printed,
              expressed as an fsb.  The type is set to data
              (uninterpreted). XFS filesystem block numbers are computed
              ((agno << agshift) | agblock) where agshift depends on the
              size of an allocation group. Use the convert command to
              convert to and from this form. Block numbers given for
              file blocks (for instance from the bmap command) are in
              this form.

       fsmap [ start ] [ end ]
              Prints the mapping of disk blocks used by an XFS
              filesystem.  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.  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.

       fuzz [-c] [-d] field action
              Write garbage into a specific structure field on disk.
              Expert mode must be enabled to use this command.  The
              operation happens immediately; there is no buffering.

              The fuzz command can take the following actions against a
              field:

                 zeroes
                     Clears all bits in the field.

                 ones
                     Sets all bits in the field.

                 firstbit
                     Flips the first bit in the field.  For a scalar
                     value, this is the highest bit.

                 middlebit
                     Flips the middle bit in the field.

                 lastbit
                     Flips the last bit in the field.  For a scalar
                     value, this is the lowest bit.

                 add Adds a small value to a scalar field.

                 sub Subtracts a small value from a scalar field.

                 random
                     Randomizes the contents of the field.

              The following switches affect the write behavior:

                 -c  Skip write verifiers and CRC recalculation; allows
                     invalid data to be written to disk.

                 -d  Skip write verifiers but perform CRC recalculation;
                     allows invalid data to be written to disk to test
                     detection of invalid data.

       hash string
              Prints the hash value of string using the hash function of
              the XFS directory and attribute implementation.

       help [command]
              Print help for one or all commands.

       info   Displays selected geometry information about the
              filesystem.  The output will have the same format that
              mkfs.xfs(8) prints when creating a filesystem or
              xfs_info(8) prints when querying a filesystem.

       inode [inode#]
              Set the current inode number. If no inode# is given, print
              the current inode number.

       label [label]
              Set the filesystem label. The filesystem label can be used
              by mount(8) instead of using a device special file.  The
              maximum length of an XFS label is 12 characters - use of a
              longer label will result in truncation and a warning will
              be issued. If no label is given, the current filesystem
              label is printed.

       log [stop | start filename]
              Start logging output to filename, stop logging, or print
              the current logging status.

       logformat [-c cycle] [-s sunit]
              Reformats the log to the specified log cycle and log
              stripe unit.  This has the effect of clearing the log
              destructively.  If the log cycle is not specified, the log
              is reformatted to the current cycle.  If the log stripe
              unit is not specified, the stripe unit from the filesystem
              superblock is used.

       logres Print transaction reservation size information for each
              transaction type.  This makes it easier to find
              discrepancies in the reservation calculations between
              xfsprogs and the kernel, which will help when diagnosing
              minimum log size calculation errors.

       ls [-i] [paths]...
              List the contents of a directory.  If a path resolves to a
              directory, the directory will be listed.  If no paths are
              supplied and the IO cursor points at a directory inode,
              the contents of that directory will be listed.

              The output format is: directory cookie, inode number, file
              type, hash, name length, name.

                 -i  Resolve each of the given paths to an inode number
                     and print that number.  If no paths are given and
                     the IO cursor points to an inode, print the inode
                     number.

       metadump [-egow] filename
              Dumps metadata to a file. See xfs_metadump(8) for more
              information.

       ncheck [-s] [-i ino] ...
              Print name-inode pairs. A blockget -n command must be run
              first to gather the information.

                 -i  specifies an inode number to be printed. If no -i
                     options are given then all inodes are printed.

                 -s  specifies that only setuid and setgid files are
                     printed.

       p      See the print command.

       path dir_path
              Walk the directory tree to an inode using the supplied
              path.  Absolute and relative paths are supported.

       pop    Pop location from the stack.

       print [field-expression] ...
              Print field values.  If no argument is given, print all
              fields in the current structure.

       push [command]
              Push location to the stack. If command is supplied, set
              the current location to the results of command after
              pushing the old location.

       q      See the quit command.

       quit   Exit xfs_db.

       ring [index]
              Show position ring (if no index argument is given), or
              move to a specific entry in the position ring given by
              index.

       sb [agno]
              Set current address to SB header in allocation group agno.
              If no agno is given, use the current allocation group
              number.

       source source-file
              Process commands from source-file.  source commands can be
              nested.

       stack  View the location stack.

       type [type]
              Set the current data type to type.  If no argument is
              given, show the current data type.  The possible data
              types are: agf, agfl, agi, attr, bmapbta, bmapbtd, bnobt,
              cntbt, data, dir, dir2, dqblk, inobt, inode, log,
              refcntbt, rmapbt, rtbitmap, rtsummary, sb, symlink and
              text.  See the TYPES section below for more information on
              these data types.

       timelimit [OPTIONS]
              Print the minimum and maximum supported values for inode
              timestamps, quota expiration timers, and quota grace
              periods supported by this filesystem.  Options include:

                 --bigtime
                     Print the time limits of an XFS filesystem with the
                     bigtime feature enabled.

                 --classic
                     Print the time limits of a classic XFS filesystem.

                 --compact
                     Print all limits as raw values on a single line.

                 --pretty
                     Print the timestamps in the current locale's date
                     and time format instead of raw seconds since the
                     Unix epoch.

       uuid [uuid | generate | rewrite | restore]
              Set the filesystem universally unique identifier (UUID).
              The filesystem UUID can be used by mount(8) instead of
              using a device special file.  The uuid can be set directly
              to the desired UUID, or it can be automatically generated
              using the generate option. These options will both write
              the UUID into every copy of the superblock in the
              filesystem.  On a CRC-enabled filesystem, this will set an
              incompatible superblock flag, and the filesystem will not
              be mountable with older kernels.  This can be reverted
              with the restore option, which will copy the original UUID
              back into place and clear the incompatible flag as needed.
              rewrite copies the current UUID from the primary
              superblock to all secondary copies of the superblock.  If
              no argument is given, the current filesystem UUID is
              printed.

       version [feature | versionnum features2]
              Enable selected features for a filesystem (certain
              features can be enabled on an unmounted filesystem, after
              mkfs.xfs(8) has created the filesystem).  Support for
              unwritten extents can be enabled using the extflg option.
              Support for version 2 log format can be enabled using the
              log2 option. Support for extended attributes can be
              enabled using the attr1 or attr2 option. Once enabled,
              extended attributes cannot be disabled, but the user may
              toggle between attr1 and attr2 at will (older kernels may
              not support the newer version).

              If no argument is given, the current version and feature
              bits are printed.  With one argument, this command will
              write the updated version number into every copy of the
              superblock in the filesystem.  If two arguments are given,
              they will be used as numeric values for the versionnum and
              features2 bits respectively, and their string equivalent
              reported (but no modifications are made).

       write [-c|-d] [field value] ...
              Write a value to disk.  Specific fields can be set in
              structures (struct mode), or a block can be set to data
              values (data mode), or a block can be set to string values
              (string mode, for symlink blocks).  The operation happens
              immediately: there is no buffering.

              Struct mode is in effect when the current type is
              structural, i.e. not data. For struct mode, the syntax is
              "write field value".

              Data mode is in effect when the current type is data. In
              this case the contents of the block can be shifted or
              rotated left or right, or filled with a sequence, a
              constant value, or a random value. In this mode write with
              no arguments gives more information on the allowed
              commands.

                 -c  Skip write verifiers and CRC recalculation; allows
                     invalid data to be written to disk.

                 -d  Skip write verifiers but perform CRC recalculation.
                     This allows invalid data to be written to disk to
                     test detection of invalid data.  (This is not
                     possible for some types.)

TYPES         top

       This section gives the fields in each structure type and their
       meanings.  Note that some types of block cover multiple actual
       structures, for instance directory blocks.

       agf    The AGF block is the header for block allocation
              information; it is in the second 512-byte block of each
              allocation group.  The following fields are defined:
                     magicnum
                            AGF block magic number, 0x58414746 ('XAGF').
                     versionnum
                            version number, currently 1.
                     seqno  sequence number starting from 0.
                     length size in filesystem blocks of the allocation
                            group. All allocation groups except the last
                            one of the filesystem have the superblock's
                            agblocks value here.
                     bnoroot
                            block number of the root of the Btree
                            holding free space information sorted by
                            block number.
                     cntroot
                            block number of the root of the Btree
                            holding free space information sorted by
                            block count.
                     bnolevel
                            number of levels in the by-block-number
                            Btree.
                     cntlevel
                            number of levels in the by-block-count
                            Btree.
                     flfirst
                            index into the AGFL block of the first
                            active entry.
                     fllast index into the AGFL block of the last active
                            entry.
                     flcount
                            count of active entries in the AGFL block.
                     freeblks
                            count of blocks represented in the freespace
                            Btrees.
                     longest
                            longest free space represented in the
                            freespace Btrees.
                     btreeblks
                            number of blocks held in the AGF Btrees.

       agfl   The AGFL block contains block numbers for use of the block
              allocator; it is in the fourth 512-byte block of each
              allocation group.  Each entry in the active list is a
              block number within the allocation group that can be used
              for any purpose if space runs low.  The AGF block fields
              flfirst, fllast, and flcount designate which entries are
              currently active.  Entry space is allocated in a circular
              manner within the AGFL block.  Fields defined:
                     bno    array of all block numbers. Even those which
                            are not active are printed.

       agi    The AGI block is the header for inode allocation
              information; it is in the third 512-byte block of each
              allocation group.  Fields defined:
                     magicnum
                            AGI block magic number, 0x58414749 ('XAGI').
                     versionnum
                            version number, currently 1.
                     seqno  sequence number starting from 0.
                     length size in filesystem blocks of the allocation
                            group.
                     count  count of inodes allocated.
                     root   block number of the root of the Btree
                            holding inode allocation information.
                     level  number of levels in the inode allocation
                            Btree.
                     freecount
                            count of allocated inodes that are not in
                            use.
                     newino last inode number allocated.
                     dirino unused.
                     unlinked
                            an array of inode numbers within the
                            allocation group. The entries in the AGI
                            block are the heads of lists which run
                            through the inode next_unlinked field. These
                            inodes are to be unlinked the next time the
                            filesystem is mounted.

       attr   An attribute fork is organized as a Btree with the actual
              data embedded in the leaf blocks. The root of the Btree is
              found in block 0 of the fork.  The index (sort order) of
              the Btree is the hash value of the attribute name.  All
              the blocks contain a blkinfo structure at the beginning,
              see type dir for a description. Nonleaf blocks are
              identical in format to those for version 1 and version 2
              directories, see type dir for a description. Leaf blocks
              can refer to "local" or "remote" attribute values. Local
              values are stored directly in the leaf block.  Leaf blocks
              contain the following fields:
                     hdr    header containing a blkinfo structure info
                            (magic number 0xfbee), a count of active
                            entries, usedbytes total bytes of names and
                            values, the firstused byte in the name area,
                            holes set if the block needs compaction, and
                            array freemap as for dir leaf blocks.
                     entries
                            array of structures containing a hashval,
                            nameidx (index into the block of the name),
                            and flags incomplete, root, and local.
                     nvlist array of structures describing the attribute
                            names and values. Fields always present:
                            valuelen (length of value in bytes),
                            namelen, and name.  Fields present for local
                            values: value (value string). Fields present
                            for remote values: valueblk (fork block
                            number of containing the value).

              Remote values are stored in an independent block in the
              attribute fork.  Prior to v5, value blocks had no
              structure, but in v5 they acquired a header structure with
              the following fields:
                     magic  attr3 remote block magic number, 0x5841524d
                            ('XARM').
                     offset Byte offset of this data block within the
                            overall attribute value.
                     bytes  Number of bytes stored in this block.
                     crc    Checksum of the attribute block contents.
                     uuid   Filesystem UUID.
                     owner  Inode that owns this attribute value.
                     bno    Block offset of this block within the
                            inode's attribute fork.
                     lsn    Log serial number of the last time this
                            block was logged.
                     data   The attribute value data.

       bmapbt Files with many extents in their data or attribute fork
              will have the extents described by the contents of a Btree
              for that fork, instead of being stored directly in the
              inode.  Each bmap Btree starts with a root block contained
              within the inode.  The other levels of the Btree are
              stored in filesystem blocks.  The blocks are linked to
              sibling left and right blocks at each level, as well as by
              pointers from parent to child blocks.  Each block contains
              the following fields:
                     magic  bmap Btree block magic number, 0x424d4150
                            ('BMAP').
                     level  level of this block above the leaf level.
                     numrecs
                            number of records or keys in the block.
                     leftsib
                            left (logically lower) sibling block, 0 if
                            none.
                     rightsib
                            right (logically higher) sibling block, 0 if
                            none.
                     recs   [leaf blocks only] array of extent records.
                            Each record contains startoff, startblock,
                            blockcount, and extentflag (1 if the extent
                            is unwritten).
                     keys   [non-leaf blocks only] array of key records.
                            These are the first key value of each block
                            in the level below this one. Each record
                            contains startoff.
                     ptrs   [non-leaf blocks only] array of child block
                            pointers.  Each pointer is a filesystem
                            block number to the next level in the Btree.

       bnobt  There is one set of filesystem blocks forming the by-
              block-number allocation Btree for each allocation group.
              The root block of this Btree is designated by the bnoroot
              field in the corresponding AGF block.  The blocks are
              linked to sibling left and right blocks at each level, as
              well as by pointers from parent to child blocks.  Each
              block has the following fields:
                     magic  BNOBT block magic number, 0x41425442
                            ('ABTB').
                     level  level number of this block, 0 is a leaf.
                     numrecs
                            number of data entries in the block.
                     leftsib
                            left (logically lower) sibling block, 0 if
                            none.
                     rightsib
                            right (logically higher) sibling block, 0 if
                            none.
                     recs   [leaf blocks only] array of freespace
                            records. Each record contains startblock and
                            blockcount.
                     keys   [non-leaf blocks only] array of key records.
                            These are the first value of each block in
                            the level below this one. Each record
                            contains startblock and blockcount.
                     ptrs   [non-leaf blocks only] array of child block
                            pointers. Each pointer is a block number
                            within the allocation group to the next
                            level in the Btree.

       cntbt  There is one set of filesystem blocks forming the by-
              block-count allocation Btree for each allocation group.
              The root block of this Btree is designated by the cntroot
              field in the corresponding AGF block. The blocks are
              linked to sibling left and right blocks at each level, as
              well as by pointers from parent to child blocks. Each
              block has the following fields:
                     magic  CNTBT block magic number, 0x41425443
                            ('ABTC').
                     level  level number of this block, 0 is a leaf.
                     numrecs
                            number of data entries in the block.
                     leftsib
                            left (logically lower) sibling block, 0 if
                            none.
                     rightsib
                            right (logically higher) sibling block, 0 if
                            none.
                     recs   [leaf blocks only] array of freespace
                            records. Each record contains startblock and
                            blockcount.
                     keys   [non-leaf blocks only] array of key records.
                            These are the first value of each block in
                            the level below this one. Each record
                            contains blockcount and startblock.
                     ptrs   [non-leaf blocks only] array of child block
                            pointers. Each pointer is a block number
                            within the allocation group to the next
                            level in the Btree.

       data   User file blocks, and other blocks whose type is unknown,
              have this type for display purposes in xfs_db.  The block
              data is displayed in hexadecimal format.

       dir    A version 1 directory is organized as a Btree with the
              directory data embedded in the leaf blocks. The root of
              the Btree is found in block 0 of the file. The index (sort
              order) of the Btree is the hash value of the entry name.
              All the blocks contain a blkinfo structure at the
              beginning with the following fields:
                     forw   next sibling block.
                     back   previous sibling block.
                     magic  magic number for this block type.
              The non-leaf (node) blocks have the following fields:
                     hdr    header containing a blkinfo structure info
                            (magic number 0xfebe), the count of active
                            entries, and the level of this block above
                            the leaves.
                     btree  array of entries containing hashval and
                            before fields. The before value is a block
                            number within the directory file to the
                            child block, the hashval is the last hash
                            value in that block.
              The leaf blocks have the following fields:
                     hdr    header containing a blkinfo structure info
                            (magic number 0xfeeb), the count of active
                            entries, namebytes (total name string
                            bytes), holes flag (block needs compaction),
                            and freemap (array of base, size entries for
                            free regions).
                     entries
                            array of structures containing hashval,
                            nameidx (byte index into the block of the
                            name string), and namelen.
                     namelist
                            array of structures containing inumber and
                            name.

       dir2   A version 2 directory has four kinds of blocks.  Data
              blocks start at offset 0 in the file.  There are two kinds
              of data blocks: single-block directories have the leaf
              information embedded at the end of the block, data blocks
              in multi-block directories do not.  Node and leaf blocks
              start at offset 32GiB (with either a single leaf block or
              the root node block).  Freespace blocks start at offset
              64GiB.  The node and leaf blocks form a Btree, with
              references to the data in the data blocks.  The freespace
              blocks form an index of longest free spaces within the
              data blocks.

              A single-block directory block contains the following
              fields:
                     bhdr   header containing magic number 0x58443242
                            ('XD2B') and an array bestfree of the
                            longest 3 free spaces in the block (offset,
                            length).
                     bu     array of union structures. Each element is
                            either an entry or a freespace.  For
                            entries, there are the following fields:
                            inumber, namelen, name, and tag.  For
                            freespace, there are the following fields:
                            freetag (0xffff), length, and tag.  The tag
                            value is the byte offset in the block of the
                            start of the entry it is contained in.
                     bleaf  array of leaf entries containing hashval and
                            address.  The address is a 64-bit word
                            offset into the file.
                     btail  tail structure containing the total count of
                            leaf entries and stale count of unused leaf
                            entries.
              A data block contains the following fields:
                     dhdr   header containing magic number 0x58443244
                            ('XD2D') and an array bestfree of the
                            longest 3 free spaces in the block (offset,
                            length).
                     du     array of union structures as for bu.
              Leaf blocks have two possible forms. If the Btree consists
              of a single leaf then the freespace information is in the
              leaf block, otherwise it is in separate blocks and the
              root of the Btree is a node block. A leaf block contains
              the following fields:
                     lhdr   header containing a blkinfo structure info
                            (magic number 0xd2f1 for the single leaf
                            case, 0xd2ff for the true Btree case), the
                            total count of leaf entries, and stale count
                            of unused leaf entries.
                     lents  leaf entries, as for bleaf.
                     lbests [single leaf only] array of values which
                            represent the longest freespace in each data
                            block in the directory.
                     ltail  [single leaf only] tail structure containing
                            bestcount count of lbests.
              A node block is identical to that for types attr and dir.

              A freespace block contains the following fields:
                     fhdr   header containing magic number 0x58443246
                            ('XD2F'), firstdb first data block number
                            covered by this freespace block, nvalid
                            number of valid entries, and nused number of
                            entries representing real data blocks.
                     fbests array of values as for lbests.

       dqblk  The quota information is stored in files referred to by
              the superblock uquotino and pquotino fields. Each
              filesystem block in a quota file contains a constant
              number of quota entries. The quota entry size is currently
              136 bytes, so with a 4KiB filesystem block size there are
              30 quota entries per block. The dquot command is used to
              locate these entries in the filesystem.  The file entries
              are indexed by the user or project identifier to determine
              the block and offset.  Each quota entry has the following
              fields:
                     magic  magic number, 0x4451 ('DQ').
                     version
                            version number, currently 1.
                     flags  flags, values include 0x01 for user quota,
                            0x02 for project quota.
                     id     user or project identifier.
                     blk_hardlimit
                            absolute limit on blocks in use.
                     blk_softlimit
                            preferred limit on blocks in use.
                     ino_hardlimit
                            absolute limit on inodes in use.
                     ino_softlimit
                            preferred limit on inodes in use.
                     bcount blocks actually in use.
                     icount inodes actually in use.
                     itimer time when service will be refused if soft
                            limit is violated for inodes.
                     btimer time when service will be refused if soft
                            limit is violated for blocks.
                     iwarns number of warnings issued about inode limit
                            violations.
                     bwarns number of warnings issued about block limit
                            violations.
                     rtb_hardlimit
                            absolute limit on realtime blocks in use.
                     rtb_softlimit
                            preferred limit on realtime blocks in use.
                     rtbcount
                            realtime blocks actually in use.
                     rtbtimer
                            time when service will be refused if soft
                            limit is violated for realtime blocks.
                     rtbwarns
                            number of warnings issued about realtime
                            block limit violations.

       inobt  There is one set of filesystem blocks forming the inode
              allocation Btree for each allocation group. The root block
              of this Btree is designated by the root field in the
              corresponding AGI block.  The blocks are linked to sibling
              left and right blocks at each level, as well as by
              pointers from parent to child blocks.  Each block has the
              following fields:
                     magic  INOBT block magic number, 0x49414254
                            ('IABT').
                     level  level number of this block, 0 is a leaf.
                     numrecs
                            number of data entries in the block.
                     leftsib
                            left (logically lower) sibling block, 0 if
                            none.
                     rightsib
                            right (logically higher) sibling block, 0 if
                            none.
                     recs   [leaf blocks only] array of inode records.
                            Each record contains startino allocation-
                            group relative inode number, freecount count
                            of free inodes in this chunk, and free
                            bitmap, LSB corresponds to inode 0.
                     keys   [non-leaf blocks only] array of key records.
                            These are the first value of each block in
                            the level below this one. Each record
                            contains startino.
                     ptrs   [non-leaf blocks only] array of child block
                            pointers. Each pointer is a block number
                            within the allocation group to the next
                            level in the Btree.

       inode  Inodes are allocated in "chunks" of 64 inodes each.
              Usually a chunk is multiple filesystem blocks, although
              there are cases with large filesystem blocks where a chunk
              is less than one block. The inode Btree (see inobt above)
              refers to the inode numbers per allocation group. The
              inode numbers directly reflect the location of the inode
              block on disk. Use the inode command to point xfs_db to a
              specific inode. Each inode contains four regions: core,
              next_unlinked, u, and a.  core contains the fixed
              information.  next_unlinked is separated from the core due
              to journaling considerations, see type agi field unlinked.
              u is a union structure that is different in size and
              format depending on the type and representation of the
              file data ("data fork").  a is an optional union structure
              to describe attribute data, that is different in size,
              format, and location depending on the presence and
              representation of attribute data, and the size of the u
              data ("attribute fork").  xfs_db automatically selects the
              proper union members based on information in the inode.

              The following are fields in the inode core:
                     magic  inode magic number, 0x494e ('IN').
                     mode   mode and type of file, as described in
                            chmod(2), mknod(2), and stat(2).
                     version
                            inode version, 1 or 2.
                     format format of u union data (0: xfs_dev_t, 1:
                            local file - in-inode directory or symlink,
                            2: extent list, 3: Btree root, 4: unique id
                            [unused]).
                     nlinkv1
                            number of links to the file in a version 1
                            inode.
                     nlinkv2
                            number of links to the file in a version 2
                            inode.
                     projid_lo
                            owner's project id (low word; version 2
                            inode only).  projid_hi owner's project id
                            (high word; version 2 inode only).
                     uid    owner's user id.
                     gid    owner's group id.
                     atime  time last accessed (seconds and
                            nanoseconds).
                     mtime  time last modified.
                     ctime  time created or inode last modified.
                     size   number of bytes in the file.
                     nblocks
                            total number of blocks in the file including
                            indirect and attribute.
                     extsize
                            basic/minimum extent size for the file.
                     nextents
                            number of extents in the data fork.
                     naextents
                            number of extents in the attribute fork.
                     forkoff
                            attribute fork offset in the inode, in
                            64-bit words from the start of u.
                     aformat
                            format of a data (1: local attribute data,
                            2: extent list, 3: Btree root).
                     dmevmask
                            DMAPI event mask.
                     dmstate
                            DMAPI state information.
                     newrtbm
                            file is the realtime bitmap and is "new"
                            format.
                     prealloc
                            file has preallocated data space after EOF.
                     realtime
                            file data is in the realtime subvolume.
                     gen    inode generation number.
              The following fields are in the u data fork union:
                     bmbt   bmap Btree root. This looks like a bmapbtd
                            block with redundant information removed.
                     bmx    array of extent descriptors.
                     dev    dev_t for the block or character device.
                     sfdir  shortform (in-inode) version 1 directory.
                            This consists of a hdr containing the parent
                            inode number and a count of active entries
                            in the directory, followed by an array list
                            of hdr.count entries. Each such entry
                            contains inumber, namelen, and name string.
                     sfdir2 shortform (in-inode) version 2 directory.
                            This consists of a hdr containing a count of
                            active entries in the directory, an i8count
                            of entries with inumbers that don't fit in a
                            32-bit value, and the parent inode number,
                            followed by an array list of hdr.count
                            entries. Each such entry contains namelen, a
                            saved offset used when the directory is
                            converted to a larger form, a name string,
                            and the inumber.
                     symlink
                            symbolic link string value.
              The following fields are in the a attribute fork union if
              it exists:
                     bmbt   bmap Btree root, as above.
                     bmx    array of extent descriptors.
                     sfattr shortform (in-inode) attribute values. This
                            consists of a hdr containing a totsize
                            (total size in bytes) and a count of active
                            entries, followed by an array list of
                            hdr.count entries. Each such entry contains
                            namelen, valuelen, root flag, name, and
                            value.

       log    Log blocks contain the journal entries for XFS.  It's not
              useful to examine these with xfs_db, use xfs_logprint(8)
              instead.

       refcntbt
              There is one set of filesystem blocks forming the
              reference count Btree for each allocation group. The root
              block of this Btree is designated by the refcntroot field
              in the corresponding AGF block.  The blocks are linked to
              sibling left and right blocks at each level, as well as by
              pointers from parent to child blocks.  Each block has the
              following fields:
                     magic  REFC block magic number, 0x52334643
                            ('R3FC').
                     level  level number of this block, 0 is a leaf.
                     numrecs
                            number of data entries in the block.
                     leftsib
                            left (logically lower) sibling block, 0 if
                            none.
                     rightsib
                            right (logically higher) sibling block, 0 if
                            none.
                     recs   [leaf blocks only] array of reference count
                            records. Each record contains startblock,
                            blockcount, and refcount.
                     keys   [non-leaf blocks only] array of key records.
                            These are the first value of each block in
                            the level below this one. Each record
                            contains startblock.
                     ptrs   [non-leaf blocks only] array of child block
                            pointers. Each pointer is a block number
                            within the allocation group to the next
                            level in the Btree.

       rmapbt There is one set of filesystem blocks forming the reverse
              mapping Btree for each allocation group. The root block of
              this Btree is designated by the rmaproot field in the
              corresponding AGF block.  The blocks are linked to sibling
              left and right blocks at each level, as well as by
              pointers from parent to child blocks.  Each block has the
              following fields:
                     magic  RMAP block magic number, 0x524d4233
                            ('RMB3').
                     level  level number of this block, 0 is a leaf.
                     numrecs
                            number of data entries in the block.
                     leftsib
                            left (logically lower) sibling block, 0 if
                            none.
                     rightsib
                            right (logically higher) sibling block, 0 if
                            none.
                     recs   [leaf blocks only] array of reference count
                            records. Each record contains startblock,
                            blockcount, owner, offset, attr_fork,
                            bmbt_block, and unwritten.
                     keys   [non-leaf blocks only] array of double-key
                            records. The first ("low") key contains the
                            first value of each block in the level below
                            this one. The second ("high") key contains
                            the largest key that can be used to identify
                            any record in the subtree. Each record
                            contains startblock, owner, offset,
                            attr_fork, and bmbt_block.
                     ptrs   [non-leaf blocks only] array of child block
                            pointers. Each pointer is a block number
                            within the allocation group to the next
                            level in the Btree.

       rtbitmap
              If the filesystem has a realtime subvolume, then the
              rbmino field in the superblock refers to a file that
              contains the realtime bitmap.  Each bit in the bitmap file
              controls the allocation of a single realtime extent (set
              == free). The bitmap is processed in 32-bit words, the LSB
              of a word is used for the first extent controlled by that
              bitmap word. The atime field of the realtime bitmap inode
              contains a counter that is used to control where the next
              new realtime file will start.

       rtsummary
              If the filesystem has a realtime subvolume, then the
              rsumino field in the superblock refers to a file that
              contains the realtime summary data. The summary file
              contains a two-dimensional array of 16-bit values.  Each
              value counts the number of free extent runs (consecutive
              free realtime extents) of a given range of sizes that
              starts in a given bitmap block.  The size ranges are
              binary buckets (low size in the bucket is a power of 2).
              There are as many size ranges as are necessary given the
              size of the realtime subvolume.  The first dimension is
              the size range, the second dimension is the starting
              bitmap block number (adjacent entries are for the same
              size, adjacent bitmap blocks).

       sb     There is one sb (superblock) structure per allocation
              group.  It is the first disk block in the allocation
              group.  Only the first one (block 0 of the filesystem) is
              actually used; the other blocks are redundant information
              for xfs_repair(8) to use if the first superblock is
              damaged. Fields defined:
                     magicnum
                            superblock magic number, 0x58465342
                            ('XFSB').
                     blocksize
                            filesystem block size in bytes.
                     dblocks
                            number of filesystem blocks present in the
                            data subvolume.
                     rblocks
                            number of filesystem blocks present in the
                            realtime subvolume.
                     rextents
                            number of realtime extents that rblocks
                            contain.
                     uuid   unique identifier of the filesystem.
                     logstart
                            starting filesystem block number of the log
                            (journal).  If this value is 0 the log is
                            "external".
                     rootino
                            root inode number.
                     rbmino realtime bitmap inode number.
                     rsumino
                            realtime summary data inode number.
                     rextsize
                            realtime extent size in filesystem blocks.
                     agblocks
                            size of an allocation group in filesystem
                            blocks.
                     agcount
                            number of allocation groups.
                     rbmblocks
                            number of realtime bitmap blocks.
                     logblocks
                            number of log blocks (filesystem blocks).
                     versionnum
                            filesystem version information.  This value
                            is currently 1, 2, 3, or 4 in the low 4
                            bits.  If the low bits are 4 then the other
                            bits have additional meanings.  1 is the
                            original value.  2 means that attributes
                            were used.  3 means that version 2 inodes
                            (large link counts) were used.  4 is the
                            bitmask version of the version number.  In
                            this case, the other bits are used as flags
                            (0x0010: attributes were used, 0x0020:
                            version 2 inodes were used, 0x0040: quotas
                            were used, 0x0080: inode cluster alignment
                            is in force, 0x0100: data stripe alignment
                            is in force, 0x0200: the shared_vn field is
                            used, 0x1000: unwritten extent tracking is
                            on, 0x2000: version 2 directories are in
                            use).
                     sectsize
                            sector size in bytes, currently always 512.
                            This is the size of the superblock and the
                            other header blocks.
                     inodesize
                            inode size in bytes.
                     inopblock
                            number of inodes per filesystem block.
                     fname  obsolete, filesystem name.
                     fpack  obsolete, filesystem pack name.
                     blocklog
                            log2 of blocksize.
                     sectlog
                            log2 of sectsize.
                     inodelog
                            log2 of inodesize.
                     inopblog
                            log2 of inopblock.
                     agblklog
                            log2 of agblocks (rounded up).
                     rextslog
                            log2 of rextents.
                     inprogress
                            mkfs.xfs(8) or xfs_copy(8) aborted before
                            completing this filesystem.
                     imax_pct
                            maximum percentage of filesystem space used
                            for inode blocks.
                     icount number of allocated inodes.
                     ifree  number of allocated inodes that are not in
                            use.
                     fdblocks
                            number of free data blocks.
                     frextents
                            number of free realtime extents.
                     uquotino
                            user quota inode number.
                     pquotino
                            project quota inode number; this is
                            currently unused.
                     qflags quota status flags (0x01: user quota
                            accounting is on, 0x02: user quota limits
                            are enforced, 0x04: quotacheck has been run
                            on user quotas, 0x08: project quota
                            accounting is on, 0x10: project quota limits
                            are enforced, 0x20: quotacheck has been run
                            on project quotas).
                     flags  random flags. 0x01: only read-only mounts
                            are allowed.
                     shared_vn
                            shared version number (shared readonly
                            filesystems).
                     inoalignmt
                            inode chunk alignment in filesystem blocks.
                     unit   stripe or RAID unit.
                     width  stripe or RAID width.
                     dirblklog
                            log2 of directory block size (filesystem
                            blocks).

       symlink
              Symbolic link blocks are used only when the symbolic link
              value does not fit inside the inode. The block content is
              just the string value.  Bytes past the logical end of the
              symbolic link value have arbitrary values.

       text   User file blocks, and other blocks whose type is unknown,
              have this type for display purposes in xfs_db.  The block
              data is displayed in two columns: Hexadecimal format and
              printable ASCII chars.

DIAGNOSTICS         top

       Many messages can come from the check (blockget) command.  If the
       filesystem is completely corrupt, a core dump might be produced
       instead of the message
              device is not a valid filesystem

       If the filesystem is very large (has many files) then check might
       run out of memory. In this case the message
              out of memory
       is printed.

       The following is a description of the most likely problems and
       the associated messages.  Most of the diagnostics produced are
       only meaningful with an understanding of the structure of the
       filesystem.

       agf_freeblks n, counted m in ag a
              The freeblocks count in the allocation group header for
              allocation group a doesn't match the number of blocks
              counted free.

       agf_longest n, counted m in ag a
              The longest free extent in the allocation group header for
              allocation group a doesn't match the longest free extent
              found in the allocation group.

       agi_count n, counted m in ag a
              The allocated inode count in the allocation group header
              for allocation group a doesn't match the number of inodes
              counted in the allocation group.

       agi_freecount n, counted m in ag a
              The free inode count in the allocation group header for
              allocation group a doesn't match the number of inodes
              counted free in the allocation group.

       block a/b expected inum 0 got i
              The block number is specified as a pair (allocation group
              number, block in the allocation group).  The block is used
              multiple times (shared), between multiple inodes.  This
              message usually follows a message of the next type.

       block a/b expected type unknown got y
              The block is used multiple times (shared).

       block a/b type unknown not expected

SEE ALSO         top

       mkfs.xfs(8), xfs_admin(8), xfs_copy(8), xfs_logprint(8),
       xfs_metadump(8), xfs_ncheck(8), xfs_repair(8), mount(8),
       chmod(2), mknod(2), stat(2), xfs(5).

COLOPHON         top

       This page is part of the xfsprogs (utilities for XFS filesystems)
       project.  Information about the project can be found at 
       ⟨http://xfs.org/⟩.  If you have a bug report for this manual page,
       send it to linux-xfs@vger.kernel.org.  This page was obtained
       from the project's upstream Git repository
       ⟨https://git.kernel.org/pub/scm/fs/xfs/xfsprogs-dev.git⟩ on
       2021-08-27.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-08-20.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

                                                               xfs_db(8)

Pages that refer to this page: xfs_admin(8)xfs_io(8)xfs_metadump(8)xfs_ncheck(8)