Linux tune2fs Command

Linux tune2fs Command Examples

tune2fs command


The "tune2fs" command is used by the system administrator to change/modify tunable parameters on ext2, ext3 and ext4 type filesystems. To display the current values that are set you can use the tune2fs command with the "-l" option or use the dumpe2fs command.



Basic Usage of tune2fs



Usage: tune2fs [-c max_mounts_count] [-e errors_behavior] [-g group]
        [-i interval[d|m|w]] [-j] [-J journal_options] [-l]
        [-m reserved_blocks_percent] [-o [^]mount_options[,...]]
        [-r reserved_blocks_count] [-u user] [-C mount_count] [-L volume_label]
        [-M last_mounted_dir] [-O [^]feature[,...]]
        [-E extended-option[,...]] [-T last_check_time] [-U UUID]
        [ -I new_inode_size ] device

tune2fs - View Filesystem Information


The command to display filesystem information is "tune2fs -l /dev/sdax" - (amend device name accordingly to match your system)



ls001a:~ # tune2fs -l /dev/sda1

tune2fs 1.41.9 (22-Aug-2009)
Filesystem volume name:   <none>
Last mounted on:          <not available>
Filesystem UUID:          8816cb40-7618-4596-906c-510321ef30ba
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      has_journal ext_attr resize_inode dir_index filetype needs_recovery sparse_super
Filesystem flags:         signed_directory_hash
Default mount options:    (none)
Filesystem state:         clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              40000
Block count:              159744
Reserved block count:     7987
Free blocks:              118755
Free inodes:              39955
First block:              1
Block size:               1024
Fragment size:            1024
Reserved GDT blocks:      256
Blocks per group:         8192
Fragments per group:      8192
Inodes per group:         2000
Inode blocks per group:   250
Filesystem created:       Wed Mar 21 15:17:43 2012
Last mount time:          Mon Jul 22 13:01:37 2013
Last write time:          Mon Jul 22 13:01:37 2013
Mount count:              25
Maximum mount count:      -1
Last checked:             Wed Mar 21 15:17:43 2012
Check interval:           0 (<none>)
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:               128
Journal inode:            8
Default directory hash:   half_md4
Directory Hash Seed:      a9e266b1-8c1a-4581-8409-40a036cdbd13
Journal backup:           inode blocks

Display Filesystem Volume Name


In the following example we are going to use the grep command to extract information that relates to the "Filesystem volume name"
You will need to amend the device name accordingly.



ls001a:~ # tune2fs -l /dev/sda1 | grep volume
Filesystem volume name:   <none>

Change Filesystem Volume Name


Using the "-L" parameter, we can give add/change the filesystem volume name.



ls001a:~ # tune2fs -L Disk_One /dev/sda1
tune2fs 1.41.9 (22-Aug-2009)

ls001a:~ # tune2fs -l /dev/sda1 | grep volume
Filesystem volume name:   Disk_One


Displaying Filesystem Check Intervals and Mount Counts


By default, most systems will automatically attempt to check your filesystems after a defined time limit. This may be the number of times a filesystem has been mounted or literally a set time. To display the current settings we can use the "tune2fs" command and grep for " interval" and "count".



john@john-desktop:~$ sudo tune2fs -l /dev/sda1 |grep interval
Check interval:           15552000 (6 months)

john@john-desktop:~$ sudo tune2fs -l /dev/sda1 |grep -i count
Inode count:              9609216
Block count:              38419456
Reserved block count:     1920972
Mount count:              6
Maximum mount count:      35

Disable Filesystem Check on Boot


The following parameters should only be used in a test environment where you may be carrying out multiple reboots during the course of the day. The Mount Count and check interval values below are set to "-1" which disables any checking!



tune2fs -c -1 /dev/sda1

tune2fs -i -1 /dev/sda1

Modifying Filesystem Checks


The following will modify the Check interval and Mount Count to only check after 100 mounts or a 2 month period.



tune2fs -c 100 -i 2m /dev/sda1

Staggering the mount counts at which filesystems are checked can avoid all filesystems being checked at one time. This will avoid all filesystems being checked at the same time and can reduce boot time.


tune2fs Popular Options


For a full list of available options consult the man pages: man tune2fs



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.


       -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.

       -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.

              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.

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

              It is strongly recommended that either -c (mount-count-dependent)  or  -i  (time-depen-
              dent)  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.

      -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 char-
              acters 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 pro-
              cesses.   Reserving some number of filesystem blocks for use by privileged processes is
              done  to  avoid  filesystem  fragmentation,  and  to allow system daemons, such as sys-
              logd(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%.

      -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 prob-
              lems, 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 inter-
              national 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 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 fol-
              lowing:

                   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.