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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.
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.
-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 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.
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.
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 2018-02-02.
(At that time, the date of the most recent commit that was found in
the repository was 2018-01-03.) If you discover any rendering prob‐
lems in this HTML version of the page, or you believe there is a bet‐
ter 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 1.43.8 January 2018 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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