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xfs_admin(8)                System Manager's Manual               xfs_admin(8)
NAME
       xfs_admin - change parameters of an XFS filesystem
SYNOPSIS
       xfs_admin [ -eflpu ] [ -c 0|1 ] [ -L label ] [ -U uuid ] device
       xfs_admin -V
DESCRIPTION
       xfs_admin  uses the xfs_db(8) command to modify various parameters of a
       filesystem.
       Devices that are  mounted  cannot  be  modified.   Administrators  must
       unmount  filesystems  before xfs_admin or xfs_db(8) can convert parame-
       ters.  A number of parameters of a mounted filesystem can  be  examined
       and modified using the xfs_growfs(8) command.
OPTIONS
       -e     Enables  unwritten  extent support on a filesystem that does not
              already have this enabled (for legacy filesystems, it  can't  be
              disabled anymore at mkfs time).
       -f     Specifies that the filesystem image to be processed is stored in
              a regular file at device (see the mkfs.xfs -d file option).
       -j     Enables version 2 log format (journal format  supporting  larger
              log buffers).
       -l     Print the current filesystem label.
       -p     Enable 32bit project identifier support (PROJID32BIT feature).
       -u     Print  the  current  filesystem UUID (Universally Unique IDenti-
              fier).
       -c 0|1 Enable (1) or disable (0) lazy-counters in the filesystem.
              Lazy-counters may  not  be  disabled  on  Version  5  superblock
              filesystems (i.e. those with metadata CRCs enabled).
              This operation may take quite a bit of time on large filesystems
              as the entire filesystem needs to be scanned when this option is
              changed.
              With  lazy-counters  enabled,  the superblock is not modified or
              logged on every change of the  free-space  and  inode  counters.
              Instead,  enough  information  is  kept  in  other  parts of the
              filesystem to be able to maintain  the  counter  values  without
              needing  to  keep them in the superblock. This gives significant
              improvements in performance on some configurations and  metadata
              intensive workloads.
       -L label
              Set the filesystem label to label.  XFS filesystem labels can be
              at most 12 characters long; if label is longer than  12  charac-
              ters,  xfs_admin  will  truncate it and print a warning message.
              The filesystem label can be cleared using the special "--" value
              for label.
       -U uuid
              Set  the  UUID  of  the filesystem to uuid.  A sample UUID looks
              like this: "c1b9d5a2-f162-11cf-9ece-0020afc76f16".  The uuid may
              also  be  nil,  which  will  set the filesystem UUID to the null
              UUID.  The uuid may also be generate, which will generate a  new
              UUID  for the filesystem.  Note that on CRC-enabled filesystems,
              this will set an incompatible flag such that older kernels  will
              not  be able to mount the filesystem.  To remove this incompati-
              ble flag, use restore, which will restore the original UUID  and
              remove the incompatible feature flag as needed.
       -V     Prints the version number and exits.
       The mount(8) manual entry describes how to mount a filesystem using its
       label or UUID, rather than its block special device name.
SEE ALSO
       mkfs.xfs(8), mount(8), xfs_db(8), xfs_growfs(8), xfs_repair(8), xfs(5).
                                                                  xfs_admin(8)