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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | BUGS | AUTHOR | AVAILABILITY | SEE ALSO | COLOPHON |
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TUNE2FS(8) System Manager's Manual TUNE2FS(8)
tune2fs - adjust tunable filesystem parameters on ext2/ext3/ext4
filesystems
tune2fs [ -l ] [ -c max-mount-counts ] [ -e errors-behavior ] [
-f ] [ -i interval-between-checks ] [ -I new_inode_size ] [ -j ]
[ -J journal-options ] [ -m reserved-blocks-percentage ] [ -o
[^]mount-options[,...] ] [ -r reserved-blocks-count ] [ -u user
] [ -g group ] [ -C mount-count ] [ -E extended-options ] [ -L
volume-label ] [ -M last-mounted-directory ] [ -O
[^]feature[,...] ] [ -Q quota-options ] [ -T time-last-checked ]
[ -U UUID ] [ -z undo_file ] device
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-label" or
"UUID=uuid". (i.e., LABEL=home or UUID=e40486c6-84d5-4f2f-
b99c-032281799c9d).
-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 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.
force_fsck
Set a flag in the filesystem superblock
indicating that errors have been found. This
will force fsck to run at the next mount.
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.
There are pros and cons to disabling these periodic
checks; see the discussion under the -c (mount-count-
dependent check) option for details.
-I Change the inode size used by the file system. This
requires rewriting the inode table, so it requires that
the file system is checked for consistency first using
e2fsck(8). This operation can also take a while and the
file system can be corrupted and data lost if it is
interrupted while in the middle of converting the file
system. Backing up the file system before changing inode
size is recommended.
File systems with an inode size of 128 bytes do not
support timestamps beyond January 19, 2038. Inodes which
are 256 bytes or larger will support extended timestamps,
project id's, and the ability to store some extended
attributes in the inode table for improved performance.
-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 10,240,000 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:
64bit Enable the file system to be larger than 2^32
blocks.
dir_index
Use hashed b-trees to speed up lookups for
large directories.
dir_nlink
Allow more than 65000 subdirectories per
directory.
ea_inode
Allow the value of each extended attribute to
be placed in the data blocks of a separate
inode if necessary, increasing the limit on
the size and number of extended attributes per
file. Tune2fs currently only supports setting
this filesystem feature.
encrypt
Enable support for file system level
encryption. Tune2fs currently only supports
setting this filesystem feature.
extent Enable the use of extent trees to store the
location of data blocks in inodes. Tune2fs
currently only supports setting this
filesystem feature.
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.
large_dir
Increase the limit on the number of files per
directory. Tune2fs currently only supports
setting this filesystem feature.
huge_file
Support files larger than 2 terabytes in size.
large_file
Filesystem can contain files that are greater
than 2GB.
metadata_csum
Store a checksum to protect the contents in
each metadata block.
metadata_csum_seed
Allow the filesystem to store the metadata
checksum seed in the superblock, enabling the
administrator to change the UUID of a
filesystem using the metadata_csum feature
while it is mounted.
mmp Enable or disable multiple mount protection
(MMP) feature.
project
Enable project ID tracking. This is used for
project quota tracking.
quota Enable internal file system quota inodes.
read-only
Force the kernel to mount the file system
read-only.
resize_inode
Reserve space so the block group descriptor
table may grow in the future. Tune2fs only
supports clearing this filesystem feature.
sparse_super
Limit the number of backup superblocks to save
space on large filesystems. Tune2fs currently
only supports setting this filesystem feature.
stable_inodes
Prevent the filesystem from being shrunk or
having its UUID changed, in order to allow the
use of specialized encryption settings that
make use of the inode numbers and UUID.
Tune2fs currently only supports setting this
filesystem feature.
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. The
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.
verity Enable support for verity protected files.
Tune2fs currently only supports setting this
filesystem feature.
After setting or clearing sparse_super, uninit_bg,
filetype, or resize_inode filesystem features, the file
system may require being checked using e2fsck(8) 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.
-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.
[^]prjquota
Sets/clears project 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.
-z undo_file
Before overwriting a file system block, write the old
contents of the block to an undo file. This undo file can
be used with e2undo(8) to restore the old contents of the
file system should something go wrong. If the empty
string is passed as the undo_file argument, the undo file
will be written to a file named tune2fs-device.e2undo in
the directory specified via the E2FSPROGS_UNDO_DIR
environment variable.
WARNING: The undo file cannot be used to recover from a
power or system crash.
We haven't found any bugs yet. That doesn't mean there aren't
any...
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>.
tune2fs is part of the e2fsprogs package and is available from
http://e2fsprogs.sourceforge.net.
debugfs(8), dumpe2fs(8), e2fsck(8), mke2fs(8), ext4(5)
This page is part of the e2fsprogs (utilities for ext2/3/4
filesystems) project. Information about the project can be found
at ⟨http://e2fsprogs.sourceforge.net/⟩. It is not known how to
report bugs for this man page; if you know, please send a mail to
man-pages@man7.org. This page was obtained from the project's
upstream Git repository
⟨git://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git⟩ on
2020-12-18. (At that time, the date of the most recent commit
that was found in the repository was 2020-10-01.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
E2fsprogs version 1.46-WIP March 2020 TUNE2FS(8)
Pages that refer to this page: ext4(5), mke2fs.conf(5), debugfs(8), dumpe2fs(8), e2fsck(8), e2label(8), e2undo(8), fsadm(8), mke2fs(8), mount(8), tune2fs(8)
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