huschi.net

BTRFSTUNE(8)                     Btrfs Manual                     BTRFSTUNE(8)

NAME
       btrfstune - tune various filesystem parameters
SYNOPSIS
       btrfstune [options] <dev> [<dev>...]
DESCRIPTION
       btrfstune can be used to enable, disable or set various filesystem
       parameters. The filesystem must be unmounted.
       The common usecase is to enable features that were not enabled at mkfs
       time. Please make sure that you have kernel support for the features.
       You can find a complete list of features and kernel version of their
       introduction at
       https://btrfs.wiki.kernel.org/index.php/Changelog#By_feature . Also,
       the manual page mkfs.btrfs(8) contains more details about the features.
       Some of the features could be enabled on a mounted filesystem. Please
       refer to the respective section in btrfs(5).
OPTIONS
       -S <0|1>
           Enable seeding on a given device. Value 1 will enable seeding, 0
           will disable it.
           A seeding filesystem is forced to be mounted read-only. A new
           device can be added to the filesystem and will capture all writes
           keeping the seeding device intact.
       -r
           (since kernel: 3.7)
           Enable extended inode refs (hardlink limit per file in a directory
           is 65536), enabled by mkfs feature extref. -x:: (since kernel:
           3.10)
           Enable skinny metadata extent refs (more efficient representation
           of extents), enabled by mkfs feature skinny-metadata.
           All newly created extents will use the new representation. To
           completely switch the entire filesystem, run a full balance of the
           metadata. Please refer to btrfs-balance(8). -n:: (since kernel:
           3.14)
           Enable no-holes feature (more efficient representation of file
           holes), enabled by mkfs feature no-holes. -f:: Allow dangerous
           changes, e.g. clear the seeding flag or change fsid. Make sure that
           you are aware of the dangers. -u:: Change fsid to a randomly
           generated UUID or continue previous fsid change operation in case
           it was interrupted. -U <UUID>:: Change fsid to UUID.
           The UUID should be a 36 bytes string in printf(3) format
           "%08x-%04x-%04x-%04x-%012x". If there is a previous unfinished fsid
           change, it will continue only if the UUID matches the unfinished
           one or if you use the option -u.
           Warning
           Cancelling or interrupting a UUID change operation will make the
           filesystem temporarily unmountable. To fix it, rerun btrfstune -u
           to restore the UUID and let it complete.
           Warning
           Clearing the seeding flag on a device may be dangerous. If a
           previously-seeding device is changed, all filesystems that used
           that device will become unmountable. Setting the seeding flag back
           will not fix that. A valid usecase is seeding device as a base
           image. Clear the seeding flag, update the filesystem and make it
           seeding again, provided that it's OK to throw away all filesystems
           built on top of the previous base.
EXIT STATUS
       btrfstune returns 0 if no error happened, 1 otherwise.
COMPATIBILITY NOTE
       This tool exists for historical reasons but is still in use today. The
       functionality is about to be merged to the main tool someday and
       btrfstune will become deprecated and removed afterwards.
SEE ALSO
       btrfs(5), btrfs-balance(8), mkfs.btrfs(8)

Btrfs v4.9.1                      08/06/2017                      BTRFSTUNE(8)