tune2fs - adjust tunable file system parameters on ext2/ext3/ext4 file systems
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 file
system parameters on Linux ext2, ext3, or ext4 file systems. The current
values of these options can be displayed by using the
-l option to
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 file system
will be checked by e2fsck(8). If max-mount-counts is the
string "random", tune2fs will use a random value between 20 and
40. If max-mount-counts is 0 or -1, the number of times the file
system is mounted will be disregarded by e2fsck(8) and the kernel.
Staggering the mount-counts at which file systems are forcibly checked will
avoid all file systems being checked at one time when using journaled file
systems.
Mount-count-dependent checking is disabled by default to avoid unanticipated
long reboots while e2fsck does its work. If you are concerned about file
system corruptions caused by potential hardware problems of kernel bugs, a
better solution than mount-count-dependent checking is to use the
e2scrub(8) program. This does require placing the file system on an
LVM volume, however.
-
-C mount-count
- Set the number of times the file system 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 file system at the next
reboot.
-
-e error-behavior
- Change the behavior of the kernel code when errors are
detected. In all cases, a file system error will cause e2fsck(8) to
check the file system on the next boot. error-behavior can be one
of the following:
- continue
- Continue normal execution.
- remount-ro
- Remount file system read-only.
- panic
- Cause a kernel panic.
-
-E extended-options
- Set extended options for the file system. 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 file system 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 file system for a RAID array with
stride-size file system blocks. This is the number of blocks read
or written to disk before moving to next disk. This mostly affects
placement of file system 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 file system for a RAID array with
stripe-width file system 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 file systems with
hashed b-tree directories. Valid algorithms accepted are: legacy,
half_md4, and tea.
-
encoding=encoding-name
- Enable the casefold feature in the super block and
set encoding-name as the encoding to be used. If
encoding-name is not specified, utf8 is used. The encoding cannot
be altered if casefold was previously enabled.
-
encoding_flags=encoding-flags
- Define parameters for file name character encoding
operations. If a flag is not changed using this parameter, its default
value is used. encoding-flags should be a comma-separated lists of
flags to be enabled. The flags cannot be altered if casefold was
previously enabled.
The only flag that can be set right now is strict which means that
invalid strings should be rejected by the file system. In the default
configuration, the strict flag is disabled.
-
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.
-
orphan_file_size=size
- Set size of the file for tracking unlinked but still open
inodes and inodes with truncate in progress. Larger file allows for better
scalability, reserving a few blocks per cpu is ideal.
- force_fsck
- Set a flag in the file system superblock indicating that
errors have been found. This will force fsck to run at the next
mount.
- test_fs
- Set a flag in the file system superblock indicating that it
may be mounted using experimental kernel code, such as the ext4dev file
system.
- ^test_fs
- Clear the test_fs flag, indicating the file system should
only be mounted using production-level file system code.
- -f
- Force the tune2fs operation to complete even in the face of
errors. This option is useful when removing the has_journal file
system feature from a file system 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 file system appears to require
journal replay, the -f flag must be specified twice to proceed.
WARNING: Removing an external journal from a file system which was
not cleanly unmounted without first replaying the external journal can
result in severe data loss and file system corruption.
-
-g group
- Set the group which can use the reserved file system
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 file system 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 file system. 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 file system)
stored within the file system. 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
file system, an immutable file, .journal, will be created in the
top-level directory of the file system, as it is the only safe way to
create the journal inode while the file system is mounted. While the ext3
journal is visible, it is not safe to delete it, or modify it while the
file system is mounted; for this reason the file is marked immutable.
While checking unmounted file systems, e2fsck(8) will automatically
move .journal files to the invisible, reserved journal inode. For
all file systems except for the root file system, this should happen
automatically and naturally during the next reboot cycle. Since the root
file system 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 file system to ext3 if the /etc/fstab file specifies the ext3
file system for the root file system in order to avoid requiring the use
of a rescue floppy to add an ext3 journal to the root file system.
-
-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 file system of size
journal-size megabytes. The size of the journal must be at least
1024 file system blocks (i.e., 1MB if using 1k blocks, 4MB if using 4k
blocks, etc.) and may be no more than 10,240,000 file system blocks. There
must be enough free space in the file system to create a journal of that
size.
-
fast_commit_size=fast-commit-size
- Create an additional fast commit journal area of size
fast-commit-size kilobytes. This option is only valid if
fast_commit feature is enabled on the file system. If this option
is not specified and if fast_commit feature is turned on, fast
commit area size defaults to journal-size / 64 megabytes. The total
size of the journal with fast_commit feature set is
journal-size + ( fast-commit-size * 1024) megabytes. The
total journal size may be no more than 10,240,000 file system blocks or
half the total file system size (whichever is smaller).
-
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 file system 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 file systems which will be using it. In addition,
while there is support for attaching multiple file systems 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
.
- Only one of the size or device options can be
given for a file system.
- -l
- List the contents of the file system superblock, including
the current values of the parameters that can be set via this
program.
-
-L volume-label
- Set the volume label of the file system. Ext2 file system
labels can be at most 16 characters long; if volume-label is longer
than 16 characters, tune2fs will truncate it and print a warning.
For other file systems that support online label manipulation and are
mounted tune2fs will work as well, but it will not attempt to
truncate the volume-label at all. 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 file system which may only be
allocated by privileged processes. Reserving some number of file system
blocks for use by privileged processes is done to avoid file system
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 file system. Normally, the default
percentage of reserved blocks is 5%.
-
-M last-mounted-directory
- Set the last-mounted directory for the file system.
-
-o [^]mount-option[,...]
- Set or clear the indicated default mount options in the
file system. 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 file system's superblock; mount
options without a prefix character or prefixed with a plus character ('+')
will be added to the file system.
- The following mount options can be set or cleared using
tune2fs:
- debug
- Enable debugging code for this file system.
- 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 file system is mounted with journaling enabled,
all data (not just metadata) is committed into the journal prior to being
written into the main file system.
- journal_data_ordered
- When the file system is mounted with journaling 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 file system is mounted with journaling enabled,
data may be written into the main file system 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 file system features (options)
in the file system. More than one file system feature can be cleared or
set by separating features with commas. File System features prefixed with
a caret character ('^') will be cleared in the file system's superblock;
file system features without a prefix character or prefixed with a plus
character ('+') will be added to the file system. For a detailed
description of the file system features, please see the man page
ext4(5).
- The following file system features can be set or cleared
using tune2fs:
- 64bit
- Enable the file system to be larger than 2^32 blocks.
- casefold
- Enable support for file system level casefolding. The
option can be cleared only if filesystem has no directories with F
attribute.
- 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 file system feature.
- encrypt
- Enable support for file system level encryption.
Tune2fs currently only supports setting this file system
feature.
- extent
- Enable the use of extent trees to store the location of
data blocks in inodes. Tune2fs currently only supports setting this
file system 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 file system consistency even across
unclean shutdowns. Setting the file system feature is equivalent to using
the -j option.
- fast_commit
- Enable fast commit journaling feature to improve fsync
latency.
- large_dir
- Increase the limit on the number of files per directory.
Tune2fs currently only supports setting this file system
feature.
- huge_file
- Support files larger than 2 terabytes in size.
- large_file
- File System 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 file system to store the metadata checksum seed
in the superblock, enabling the administrator to change the UUID of a file
system 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 file system
feature.
- sparse_super
- Limit the number of backup superblocks to save space on
large file systems. Tune2fs currently only supports setting this
file system feature.
- stable_inodes
- Prevent the file system 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 file system 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 file
system, 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 file system feature.
- After setting or clearing sparse_super,
uninit_bg, filetype, or resize_inode file system
features, the file system may require being checked using e2fsck(8)
to return the file system 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 file system features may prevent the file system 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 file system.
-
-r reserved-blocks-count
- Set the number of reserved file system 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 file system 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 file system, and then check the file system
during off hours to make sure it hasn't been corrupted due to hardware
problems, etc. If the file system was clean, then this option can be used
to set the last checked time on the original file system. 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 file system 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 file
system 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 file system 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 <
[email protected]>. It is
currently being maintained by Theodore Ts'o <
[email protected]>.
tune2fs uses the ext2fs library written by Theodore Ts'o
<
[email protected]>. This manual page was written by Christian Kuhtz
<
[email protected]>. Time-dependent checking was added by Uwe Ohse
<
[email protected]>.
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)