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

```
[linuxstudy@xxxx ~]$ sudo tune2fs -l /dev/sda
tune2fs 1.42.9 (28-Dec-2013)
tune2fs: Bad magic number in super-block while trying to open /dev/sda
Couldn't find valid filesystem superblock.
[linuxstudy@xxxx ~]$ sudo tune2fs -i 2w /dev/sdb1    //2週間ごとにファイルシステムをチェック
tune2fs 1.42.9 (28-Dec-2013)
Setting interval between checks to 1209600 seconds
```
```
TUNE2FS(8)                                                                                 System Manager's Manual                                                                                 TUNE2FS(8)



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.

              Mount-count-dependent  checking  is disabled by default to avoid unanticipated long reboots while e2fsck does its work.  However, you may wish to 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  jour‐
              naling  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 speci‐
              fied 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.

              There are pros and cons to disabling these periodic checks; see the discussion under the -c (mount-count-dependent check) option for details.

       -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 filesys‐
              tem) 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.

                   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 filesys‐
                          tems 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.  Nor‐
              mally, 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  argu‐
              ments 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  pur‐
                          poses.  (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.

                   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)



E2fsprogs version 1.42.9                                                                        December 2013                                                                                      TUNE2FS(8)```