xenial (8) tune2fs.8.gz

Provided by: e2fsprogs_1.42.13-1ubuntu1.2_amd64 bug

NAME

       tune2fs - adjust tunable filesystem parameters on ext2/ext3/ext4 filesystems

SYNOPSIS

       tune2fs  [ -l ] [ -c max-mount-counts ] [ -e errors-behavior ] [ -f ] [ -i interval-between-checks ] [ -j
       ] [ -J journal-options ] [ -m reserved-blocks-percentage ] [ -o [^]mount-options[,...]  ] [ -r  reserved-
       blocks-count ] [ -s sparse-super-flag ] [ -u user ] [ -g group ] [ -C mount-count ] [ -E extended-options
       ] [ -L volume-name ] [ -M last-mounted-directory ] [ -O [^]feature[,...]  ] [ -Q  quota-options  ]  [  -T
       time-last-checked ] [ -U UUID ] device

DESCRIPTION

       tune2fs  allows  the  system administrator to adjust various tunable filesystem parameters on Linux ext2,
       ext3, or ext4 filesystems.  The current values of these options can be displayed by using the  -l  option
       to tune2fs(8) program, or by using the dumpe2fs(8) program.

       The  device  specifier  can  either  be  a  filename  (i.e.,  /dev/sda1),  or  a LABEL or UUID specifier:
       "LABEL=volume-name" or "UUID=uuid".  (i.e., LABEL=home or UUID=e40486c6-84d5-4f2f-b99c-032281799c9d).

OPTIONS

       -c max-mount-counts
              Adjust the number of mounts after which the filesystem will be  checked  by  e2fsck(8).   If  max-
              mount-counts  is  0  or  -1,  the number of times the filesystem is mounted will be disregarded by
              e2fsck(8) and the kernel.

              Staggering the mount-counts at which filesystems are forcibly checked will avoid  all  filesystems
              being checked at one time when using journaled filesystems.

              You  should  strongly  consider  the  consequences  of  disabling  mount-count-dependent  checking
              entirely.  Bad disk drives, cables, memory, and kernel bugs could all corrupt a filesystem without
              marking  the  filesystem  dirty or in error.  If you are using journaling on your filesystem, your
              filesystem will never be marked dirty, so it will not normally be  checked.   A  filesystem  error
              detected by the kernel will still force an fsck on the next reboot, but it may already be too late
              to prevent data loss at that point.

              See also the -i option for time-dependent checking.

       -C mount-count
              Set the number of times the filesystem has been mounted.  If set to a greater value than the  max-
              mount-counts  parameter  set  by  the  -c  option, e2fsck(8) will check the filesystem at the next
              reboot.

       -e error-behavior
              Change the behavior of the kernel code when errors are detected.  In all cases, a filesystem error
              will  cause  e2fsck(8) to check the filesystem on the next boot.  error-behavior can be one of the
              following:

                   continue    Continue normal execution.

                   remount-ro  Remount filesystem read-only.

                   panic       Cause a kernel panic.

       -E extended-options
              Set extended options for the filesystem.  Extended options are comma separated, and  may  take  an
              argument using the equals ('=') sign.  The following extended options are supported:

                   clear_mmp
                          Reset  the MMP block (if any) back to the clean state.  Use only if absolutely certain
                          the device is not currently mounted or being fscked, or  major  filesystem  corruption
                          can result.  Needs '-f'.

                   mmp_update_interval=interval
                          Adjust the initial MMP update interval to interval seconds.  Specifying an interval of
                          0 means to use the default interval.  The specified interval must  be  less  than  300
                          seconds.  Requires that the mmp feature be enabled.

                   stride=stride-size
                          Configure  the filesystem for a RAID array with stride-size filesystem blocks. This is
                          the number of blocks read or written to disk before moving to next disk.  This  mostly
                          affects  placement  of  filesystem  metadata  like  bitmaps at mke2fs(2) time to avoid
                          placing them on a single disk, which can hurt the performance.  It may also be used by
                          block allocator.

                   stripe_width=stripe-width
                          Configure  the  filesystem  for  a  RAID array with stripe-width filesystem blocks per
                          stripe. This is typically be stride-size * N, where N is the number of data  disks  in
                          the  RAID  (e.g.  RAID 5 N+1, RAID 6 N+2).  This allows the block allocator to prevent
                          read-modify-write of the parity in a RAID stripe if possible when the data is written.

                   hash_alg=hash-alg
                          Set the default hash algorithm used for filesystems with  hashed  b-tree  directories.
                          Valid algorithms accepted are: legacy, half_md4, and tea.

                   mount_opts=mount_option_string
                          Set a set of default mount options which will be used when the file system is mounted.
                          Unlike the bitmask-based default mount options which can  be  specified  with  the  -o
                          option,  mount_option_string is an arbitrary string with a maximum length of 63 bytes,
                          which is stored in the superblock.

                          The ext4 file system driver will first apply the bitmask-based  default  options,  and
                          then  parse  the mount_option_string, before parsing the mount options passed from the
                          mount(8) program.

                          This superblock setting is only honored in 2.6.35+ kernels; and not at all by the ext2
                          and ext3 file system drivers.

                   test_fs
                          Set  a  flag  in  the  filesystem  superblock  indicating that it may be mounted using
                          experimental kernel code, such as the ext4dev filesystem.

                   ^test_fs
                          Clear the test_fs flag,  indicating  the  filesystem  should  only  be  mounted  using
                          production-level filesystem code.

       -f     Force  the  tune2fs  operation to complete even in the face of errors.  This option is useful when
              removing the has_journal filesystem feature from a filesystem which has an external journal (or is
              corrupted  such  that  it  appears  to have an external journal), but that external journal is not
              available.   If the filesystem appears to require journal replay, the -f flag  must  be  specified
              twice to proceed.

              WARNING:  Removing  an  external journal from a filesystem which was not cleanly unmounted without
              first replaying the external journal can result in severe data loss and filesystem corruption.

       -g group
              Set the group which can use the  reserved  filesystem  blocks.   The  group  parameter  can  be  a
              numerical  gid  or  a  group  name.   If a group name is given, it is converted to a numerical gid
              before it is stored in the superblock.

       -i  interval-between-checks[d|m|w]
              Adjust the maximal time between two filesystem checks.  No suffix or d will interpret  the  number
              interval-between-checks  as  days,  m as months, and w as weeks.  A value of zero will disable the
              time-dependent checking.

              It is strongly recommended that either -c (mount-count-dependent) or -i (time-dependent)  checking
              be enabled to force periodic full e2fsck(8) checking of the filesystem.  Failure to do so may lead
              to filesystem corruption (due to bad disks, cables,  memory,  or  kernel  bugs)  going  unnoticed,
              ultimately resulting in data loss or corruption.

       -j     Add  an  ext3  journal  to the filesystem.  If the -J option is not specified, the default journal
              parameters will be used  to  create  an  appropriately  sized  journal  (given  the  size  of  the
              filesystem)  stored  within  the  filesystem.  Note that you must be using a kernel which has ext3
              support in order to actually make use of the journal.

              If this option is used to create a journal on a mounted filesystem, an immutable  file,  .journal,
              will be created in the top-level directory of the filesystem, as it is the only safe way to create
              the journal inode while the filesystem is mounted.  While the ext3 journal is visible, it  is  not
              safe  to  delete  it,  or  modify  it while the filesystem is mounted; for this reason the file is
              marked immutable.   While  checking  unmounted  filesystems,  e2fsck(8)  will  automatically  move
              .journal  files to the invisible, reserved journal inode.  For all filesystems except for the root
              filesystem,  this should happen automatically and naturally during the next reboot  cycle.   Since
              the  root  filesystem is mounted read-only, e2fsck(8) must be run from a rescue floppy in order to
              effect this transition.

              On some distributions, such as Debian, if an initial ramdisk is  used,  the  initrd  scripts  will
              automatically  convert  an  ext2 root filesystem to ext3 if the /etc/fstab file specifies the ext3
              filesystem for the root filesystem in order to avoid requiring the use of a rescue floppy  to  add
              an ext3 journal to the root filesystem.

       -J journal-options
              Override the default ext3 journal parameters. Journal options are comma separated, and may take an
              argument using the equals ('=')  sign.  The following journal options are supported:

                   size=journal-size
                          Create a journal stored in the filesystem of size journal-size megabytes.    The  size
                          of  the journal must be at least 1024 filesystem blocks (i.e., 1MB if using 1k blocks,
                          4MB if using 4k blocks, etc.)  and may be no  more  than  102,400  filesystem  blocks.
                          There must be enough free space in the filesystem to create a journal of that size.

                   location=journal-location
                          Specify  the  location  of  the  journal.  The argument journal-location can either be
                          specified as a block number, or if the number has a  units  suffix  (e.g.,  'M',  'G',
                          etc.) interpret it as the offset from the beginning of the file system.

                   device=external-journal
                          Attach  the  filesystem  to the journal block device located on external-journal.  The
                          external journal must have been already created using the command

                          mke2fs -O journal_dev external-journal

                          Note that external-journal must be formatted with the same block size  as  filesystems
                          which  will  be  using it.  In addition, while there is support for attaching multiple
                          filesystems to a single external journal,  the  Linux  kernel  and  e2fsck(8)  do  not
                          currently support shared external journals yet.

                          Instead  of  specifying a device name directly, external-journal can also be specified
                          by either LABEL=label or UUID=UUID to locate the external journal by either the volume
                          label  or  UUID  stored  in  the  ext2  superblock  at  the start of the journal.  Use
                          dumpe2fs(8) to display a journal device's volume label and  UUID.   See  also  the  -L
                          option of tune2fs(8).

              Only one of the size or device options can be given for a filesystem.

       -l     List  the  contents  of  the filesystem superblock, including the current values of the parameters
              that can be set via this program.

       -L volume-label
              Set the volume label of the filesystem.  Ext2 filesystem labels can be at most 16 characters long;
              if  volume-label  is longer than 16 characters, tune2fs will truncate it and print a warning.  The
              volume label can be used  by  mount(8),  fsck(8),  and  /etc/fstab(5)  (and  possibly  others)  by
              specifying LABEL=volume_label instead of a block special device name like /dev/hda5.

       -m reserved-blocks-percentage
              Set  the  percentage  of  the  filesystem  which  may  only  be allocated by privileged processes.
              Reserving some number of filesystem blocks for use  by  privileged  processes  is  done  to  avoid
              filesystem fragmentation, and to allow system daemons, such as syslogd(8), to continue to function
              correctly after non-privileged processes are prevented from writing to the filesystem.   Normally,
              the default percentage of reserved blocks is 5%.

       -M last-mounted-directory
              Set the last-mounted directory for the filesystem.

       -o [^]mount-option[,...]
              Set  or clear the indicated default mount options in the filesystem.  Default mount options can be
              overridden by mount options specified either in /etc/fstab(5) or on the command line arguments  to
              mount(8).  Older kernels may not support this feature; in particular, kernels which predate 2.4.20
              will almost certainly ignore the default mount options field in the superblock.

              More than one mount option can be cleared or  set  by  separating  features  with  commas.   Mount
              options  prefixed  with  a  caret  character ('^') will be cleared in the filesystem's superblock;
              mount options without a prefix character or prefixed with a plus character ('+') will be added  to
              the filesystem.

              The following mount options can be set or cleared using tune2fs:

                   debug  Enable debugging code for this filesystem.

                   bsdgroups
                          Emulate  BSD  behavior  when  creating  new  files: they will take the group-id of the
                          directory in which they were created.  The standard System V behavior is the  default,
                          where  newly  created  files  take  on  the  fsgid  of the current process, unless the
                          directory has the setgid bit set, in which case it  takes  the  gid  from  the  parent
                          directory, and also gets the setgid bit set if it is a directory itself.

                   user_xattr
                          Enable user-specified extended attributes.

                   acl    Enable Posix Access Control Lists.

                   uid16  Disables  32-bit UIDs and GIDs.  This is for interoperability with older kernels which
                          only store and expect 16-bit values.

                   journal_data
                          When the filesystem is mounted with journalling enabled, all data (not just  metadata)
                          is committed into the journal prior to being written into the main filesystem.

                   journal_data_ordered
                          When  the  filesystem is mounted with journalling enabled, all data is forced directly
                          out to the main file system prior to its metadata being committed to the journal.

                   journal_data_writeback
                          When the filesystem is mounted with journalling enabled, data may be written into  the
                          main  filesystem  after  its  metadata  has  been  committed to the journal.  This may
                          increase throughput, however, it may allow old data to appear in files after  a  crash
                          and journal recovery.

                   nobarrier
                          The  file  system  will  be  mounted  with barrier operations in the journal disabled.
                          (This option is currently only supported by the ext4 file  system  driver  in  2.6.35+
                          kernels.)

                   block_validity
                          The  file  system will be mounted with the block_validity option enabled, which causes
                          extra checks to be performed after reading or writing  from  the  file  system.   This
                          prevents  corrupted  metadata  blocks  from  causing file system damage by overwriting
                          parts of the inode table or block group  descriptors.   This  comes  at  the  cost  of
                          increased  memory  and  CPU  overhead,  so  it is enabled only for debugging purposes.
                          (This option is currently only supported by the ext4 file  system  driver  in  2.6.35+
                          kernels.)

                   discard
                          The  file  system  will be mounted with the discard mount option.  This will cause the
                          file system driver to attempt to use the trim/discard feature of some storage  devices
                          (such  as  SSD's  and  thin-provisioned  drives  available  in some enterprise storage
                          arrays) to inform the storage device that blocks belonging to  deleted  files  can  be
                          reused  for other purposes.  (This option is currently only supported by the ext4 file
                          system driver in 2.6.35+ kernels.)

                   nodelalloc
                          The file system will be mounted with the nodelalloc mount option.  This  will  disable
                          the  delayed allocation feature.  (This option is currently only supported by the ext4
                          file system driver in 2.6.35+ kernels.)

       -O [^]feature[,...]
              Set or clear the indicated filesystem  features  (options)  in  the  filesystem.   More  than  one
              filesystem  feature can be cleared or set by separating features with commas.  Filesystem features
              prefixed with a caret character ('^') will be cleared in the filesystem's  superblock;  filesystem
              features  without  a prefix character or prefixed with a plus character ('+') will be added to the
              filesystem.  For a detailed description of the file system  features,  please  see  the  man  page
              ext4(5).

              The following filesystem features can be set or cleared using tune2fs:

                   dir_index
                          Use hashed b-trees to speed up lookups for large directories.

                   dir_nlink
                          Allow more than 65000 subdirectories per directory.

                   extent Enable the use of extent trees to store the location of data blocks in inodes.

                   extra_isize
                          Enable the extended inode fields used by ext4.

                   filetype
                          Store file type information in directory entries.

                   flex_bg
                          Allow  bitmaps and inode tables for a block group to be placed anywhere on the storage
                          media.  Tune2fs will not reorganize the location of the inode  tables  and  allocation
                          bitmaps,  as  mke2fs(8)  will  do when it creates a freshly formatted file system with
                          flex_bg enabled.

                   has_journal
                          Use a journal to ensure filesystem consistency even across unclean shutdowns.  Setting
                          the filesystem feature is equivalent to using the -j option.

                   huge_file
                          Support files larger than 2 terabytes in size.

                   large_file
                          Filesystem can contain files that are greater than 2GB.

                   resize_inode
                          Reserve  space  so  the  block group descriptor table may grow in the future.  Tune2fs
                          only supports clearing this filesystem feature.

                   mmp    Enable or disable multiple mount protection (MMP) feature.

                   quota  Enable internal file system quota inodes.

                   sparse_super
                          Limit the number of backup superblocks to save space on large filesystems.

                   uninit_bg
                          Allow the kernel to initialize bitmaps and inode tables lazily, and  to  keep  a  high
                          watermark for the unused inodes in a filesystem, to reduce e2fsck(8) time.  This first
                          e2fsck run after enabling this feature will take the full time, but subsequent  e2fsck
                          runs  will  take  only a fraction of the original time, depending on how full the file
                          system is.

              After setting or clearing sparse_super, uninit_bg, filetype, or resize_inode filesystem  features,
              e2fsck(8)  must  be run on the filesystem to return the filesystem to a consistent state.  Tune2fs
              will print a message requesting that the system administrator run e2fsck(8) if  necessary.   After
              setting  the dir_index feature, e2fsck -D can be run to convert existing directories to the hashed
              B-tree format.  Enabling certain filesystem features may prevent the filesystem from being mounted
              by kernels which do not support those features.  In particular, the uninit_bg and flex_bg features
              are only supported by the ext4 filesystem.

       -p mmp_check_interval
              Set the desired MMP check interval in seconds. It is 5 seconds by default.

       -r reserved-blocks-count
              Set the number of reserved filesystem blocks.

       -Q quota-options
              Sets 'quota' feature on the superblock and works on the quota files  for  the  given  quota  type.
              Quota options could be one or more of the following:

                   [^]usrquota
                          Sets/clears user quota inode in the superblock.

                   [^]grpquota
                          Sets/clears group quota inode in the superblock.

       -T time-last-checked
              Set  the  time  the  filesystem  was last checked using e2fsck.  The time is interpreted using the
              current (local) timezone.  This can be useful in scripts which use a  Logical  Volume  Manager  to
              make a consistent snapshot of a filesystem, and then check the filesystem during off hours to make
              sure it hasn't been corrupted due to hardware problems, etc.  If the filesystem  was  clean,  then
              this  option  can  be used to set the last checked time on the original filesystem.  The format of
              time-last-checked is the  international  date  format,  with  an  optional  time  specifier,  i.e.
              YYYYMMDD[HH[MM[SS]]].   The keyword now is also accepted, in which case the last checked time will
              be set to the current time.

       -u user
              Set the user who can use the reserved filesystem blocks.  user can be a numerical uid  or  a  user
              name.   If  a  user  name  is given, it is converted to a numerical uid before it is stored in the
              superblock.

       -U UUID
              Set the universally unique identifier (UUID) of the filesystem to UUID.  The format of the UUID is
              a  series  of  hex digits separated by hyphens, like this: "c1b9d5a2-f162-11cf-9ece-0020afc76f16".
              The UUID parameter may also be one of the following:

                   clear  clear the filesystem UUID

                   random generate a new randomly-generated UUID

                   time   generate a new time-based UUID

              The UUID may be used by mount(8), fsck(8), and /etc/fstab(5) (and possibly others)  by  specifying
              UUID=uuid instead of a block special device name like /dev/hda1.

              See  uuidgen(8)  for more information.  If the system does not have a good random number generator
              such as /dev/random or /dev/urandom, tune2fs will automatically use a time-based UUID instead of a
              randomly-generated UUID.

BUGS

       We haven't found any bugs yet.  That doesn't mean there aren't any...

AUTHOR

       tune2fs  was  written  by  Remy Card <Remy.Card@linux.org>.  It is currently being maintained by Theodore
       Ts'o <tytso@alum.mit.edu>.  tune2fs uses the ext2fs library written  by  Theodore  Ts'o  <tytso@mit.edu>.
       This  manual  page  was  written  by Christian Kuhtz <chk@data-hh.Hanse.DE>.  Time-dependent checking was
       added by Uwe Ohse <uwe@tirka.gun.de>.

AVAILABILITY

       tune2fs is part of the e2fsprogs package and is available from http://e2fsprogs.sourceforge.net.

SEE ALSO

       debugfs(8), dumpe2fs(8), e2fsck(8), mke2fs(8), ext4(5)