tune2fs - adjust tunable filesystem parameters on second
extended filesystems
SYNOPSIS
tune2fs [ -l ] [ -c max-mount-counts ] [ -e errors-behav
ior ] [ -i interval-between-checks ] [ -j ] [ -J journal-
options ] [ -m reserved-blocks-percentage ] [ -r reserved-
blocks-count ] [ -s sparse-super-flag ] [ -u user ] [ -g
group ] [ -C mount-count ] [ -L volume-name ] [ -M last-
mounted-directory ] [ -O [^]feature[,...] ] [ -U UUID ]
device
DESCRIPTION
tune2fs adjusts tunable filesystem parameters on a Linux
second extended filesystem.
OPTIONS
-c max-mount-counts
Adjust the maximal mounts count between two
filesystem checks. If max-mount-counts is 0 then
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. Can be used in conjunction with -c to
force an fsck on 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 fol
lowing:
remount-ro Remount filesystem read-only.
panic Cause a kernel panic.
-g group
Set the group which can use 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 postfix or d result in days, m in
months, and w in weeks. A value of zero will dis
able 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 to go unnoticed until they
cause data loss or corruption.
-j Add an ext3 journal to the filesystem. If the -J
option is not specified, the default journal param
eters 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 actu
ally make use of the journal.
-J journal-options
Override the default ext3 journal parameters. Jour
nal options are comma separated, and may take an
argument using the equals ('=') sign. The follow
ing journal options are supported:
size=journal-size
Create a journal stored in the filesys
tem 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
nal. The external journal must have
been already created using the command
mke2fs -O journal_dev external-journal
Note that external-journal must be for
matted with the same block size as
filesystems which will be using it.
Only one of the size or device options can be given
for a filesystem.
-l List the contents of the filesystem superblock.
-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.
-m reserved-blocks-percentage
Set the percentage of reserved filesystem blocks.
-M last-mounted-directory
Set the last-mounted directory for the filesystem.
-O [^]feature[,...]
Set or clear the indicated filesystem features
(options) in the filesystem. More than one
filesystem feature can be cleared or set by sepa
rating 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.
The following filesystem features can be set or
cleared using tune2fs:
sparse_super
Limit the number of backup superblocks
to save space on large filesystems.
filetype
Store file type information in direc
tory entries.
has_journal
Create an ext3 journal (as if using the
-j option).
After setting or clearing any filesystem feature,
the filesystem to a consistent state.
Warning: Linux kernels before 2.0.39 and many 2.1
series kernels do not support the filesystems that
use any of these features. Enabling certain
filesystem features may prevent the filesystem from
being mounted by kernels which do not support those
features.
-r reserved-blocks-count
Set the number of reserved filesystem blocks.
-s [0|1]
Turn the sparse super feature off or on. Turning
this feature on saves space on really big filesys
tems. This is the same as using the -O
sparse_super option.
Warning: Linux kernels before 2.0.39 do not support
this feature. Neither do all Linux 2.1 kernels;
please don't use this unless you know what you're
doing! You need to run e2fsck(8) on the filesystem
after changing this feature in order to have a
valid filesystem.
-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 hypthens, 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
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 auto
matically use a time-based UUID instead of a ran
domly-generated UUID.
BUGS
We haven't found any bugs yet. That doesn't mean there
AUTHOR
tune2fs was written by Remy Card <Remy.Card@linux.org>.
tune2fs uses the ext2fs library written by Theodore Ts'o
<tytso@mit.edu>. This manual page was written by Chris
tian Kuhtz <chk@data-hh.Hanse.DE>. Time-dependent check
ing 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
dumpe2fs(8), e2fsck(8), mke2fs(8)
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