.\"
.TH TUNE2FS 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
.SH NAME
-tune2fs \- adjust tunable filesystem parameters on second extended filesystems
+tune2fs \- adjust tunable filesystem parameters on ext2/ext3/ext4 filesystems
.SH SYNOPSIS
.B tune2fs
[
]
[
.B \-o
-.RI [^] mount-options [,...]
+.RI [^]mount-options [,...]
]
-
[
.B \-r
.I reserved-blocks-count
.I mount-count
]
[
+.B \-E
+.I extended-options
+]
+[
.B \-L
.I volume-name
]
device
.SH DESCRIPTION
.BI tune2fs
-adjusts tunable filesystem parameters on a Linux second extended filesystem.
+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
+.B -l
+option to
+.BR tune2fs (8)
+program, or by using the
+.BR dumpe2fs (8)
+program.
.SH OPTIONS
.TP
.BI \-c " max-mount-counts"
-Adjust the maximal mounts count between two filesystem checks. If
+Adjust the number of mounts after which the filesystem will be checked by
+.BR e2fsck (8).
+If
.I max-mount-counts
-is 0 then the number of times the filesystem is mounted will be disregarded
+is 0 or \-1, the number of times the filesystem is mounted will be disregarded
by
.BR e2fsck (8)
and the kernel.
.TP
.BI \-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.
+If set to a greater value than the max-mount-counts parameter
+set by the
+.B \-c
+option,
+.BR e2fsck (8)
+will check the filesystem at the next reboot.
.TP
.BI \-e " error-behavior"
Change the behavior of the kernel code when errors are detected.
Cause a kernel panic.
.RE
.TP
+.BI \-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:
+.RS 1.2i
+.TP
+.BI stride= stride-size
+Configure the filesystem for a RAID array with
+.I 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
+.BR mke2fs (2)
+time to avoid placing them on a single disk, which can hurt the performance.
+It may also be used by block allocator.
+.TP
+.BI stripe_width= stripe-width
+Configure the filesystem for a RAID array with
+.I 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.
+.TP
+.BI hash_alg= hash-alg
+Set the default hash algorithm used for filesystems with hashed b-tree
+directories. Valid algorithms accepted are:
+.IR legacy ,
+.IR half_md4 ,
+and
+.IR tea .
+.TP
+.B test_fs
+Set a flag in the filesystem superblock indicating that it may be
+mounted using experimental kernel code, such as the ext4dev filesystem.
+.TP
+.B ^test_fs
+Clear the test_fs flag, indicating the filesystem should only be mounted
+using production-level filesystem code.
+.RE
+.TP
.B \-f
Force the tune2fs operation to complete even in the face of errors. This
option is useful when removing the
severe data loss and filesystem corruption.
.TP
.BI \-g " group"
-Set the group which can use reserved filesystem blocks.
+Set the group which can use the reserved filesystem blocks.
The
.I group
parameter can be a numerical gid or a group name. If a group name is given,
(time-dependent) checking be enabled to force periodic full
.BR 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.
+corruption (due to bad disks, cables, memory, or kernel bugs) going
+unnoticed, ultimately resulting in data loss or corruption.
.TP
.B \-j
Add an ext3 journal to the filesystem. If the
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.
+.IP
+If this option is used to create a journal on a mounted filesystem, an
+immutable file,
+.BR .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,
+.BR e2fsck (8)
+will automatically move
+.B .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,
+.BR e2fsck (8)
+must be run from a rescue floppy in order to effect this transition.
+.IP
+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
+.BR /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.
.TP
.BR \-J " journal-options"
Override the default ext3 journal parameters. Journal options are comma
@JDEV@.I external-journal
@JDEV@must be formatted with the same block
@JDEV@size as filesystems which will be using it.
+@JDEV@In addition, while there is support for attaching
+@JDEV@multiple filesystems to a single external journal,
+@JDEV@the Linux kernel and
+@JDEV@.BR e2fsck (8)
+@JDEV@do not currently support shared external journals yet.
@JDEV@.IP
@JDEV@Instead of specifying a device name directly,
@JDEV@.I external-journal
@JDEV@options can be given for a filesystem.
.TP
.B \-l
-List the contents of the filesystem superblock.
+List the contents of the filesystem superblock, including the current
+values of the parameters that can be set via this program.
.TP
.BI \-L " volume-label"
Set the volume label of the filesystem.
.BR /dev/hda5 .
.TP
.BI \-m " reserved-blocks-percentage"
-Set the percentage of reserved filesystem blocks.
+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
+.BR 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%.
.TP
.BI \-M " last-mounted-directory"
Set the last-mounted directory for the filesystem.
.TP
.BR \-o " [^]\fImount-option\fR[,...]"
Set or clear the indicated default mount options in the filesystem.
-Default mount options can be overriden by mount options specified
+Default mount options can be overridden by mount options specified
either in
.BR /etc/fstab (5)
or on the command line arguments to
.B bsdgroups
Emulate BSD behaviour when creating new files: they will take the group-id
of the directory in which they were created. The standard System V behaviour
-is the default, where newly created files take on the fsgid of the crrent
-process, unless the directry has the setgid bit set, in which case it takes
+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
-directory itself.
+a directory itself.
.TP
.B user_xattr
Enable user-specified extended attributes.
.TP
.B 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 commutted
+directly out to the main file system prior to its metadata being committed
to the journal.
.TP
.B journal_data_writeback
When the filesystem is mounted with journalling enabled, data may be
-written into the main filesystem after its metadata has been commutted
+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.
.RE
.BR tune2fs :
.RS 1.2i
.TP
-.B sparse_super
-Limit the number of backup superblocks to save space on large filesystems.
+.B large_file
+Filesystem can contain files that are greater than 2GB. (Modern kernels
+set this feature automatically when a file > 2GB is created.)
+.TP
+.B dir_index
+Use hashed b-trees to speed up lookups in large directories.
.TP
.B filetype
Store file type information in directory entries.
Setting the filesystem feature is equivalent to using the
.B \-j
option.
+.TP
+.B sparse_super
+Limit the number of backup superblocks to save space on large filesystems.
+.TP
+.B resize_inode
+Reserve space so the block group descriptor table may grow in the
+future.
+.B Tune2fs
+only supports clearing this filesystem feature.
+.TP
+.B uninit_bg
+Allow the kernel to initialize bitmaps and inode tables and keep a high
+watermark for the unused inodes in a filesystem, to reduce
+.BR e2fsck (8)
+time. This 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.
.RE
.IP
After setting or clearing
-.B sparse_super
-and
-.B filetype
+.BR sparse_super ,
+.BR uninit_bg ,
+.BR filetype ,
+or
+.B resize_inode
filesystem features,
.BR e2fsck (8)
must be run on the filesystem to return the filesystem to a consistent state.
.B Tune2fs
will print a message requesting that the system administrator run
.BR e2fsck (8)
-if necessary.
-.IP
-.B 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.
+if necessary. After setting the
+.B dir_index
+feature,
+.B 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
+.BR uninit_bg
+and
+.BR flex_bg
+features are only supported by the ext4 filesystem.
.TP
.BI \-r " reserved-blocks-count"
Set the number of reserved filesystem blocks.
.TP
-.BR \-s " [" 0 | 1 ]
-Turn the sparse super feature off or on. Turning this feature on
-saves space on really big filesystems. This is the same as using the
-.B "\-O sparse_super"
-option.
-.IP
-.B 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
-.BR e2fsck (8)
-on the filesystem after changing this feature in order to have a valid
-filesystem.
-.TP
.BI \-T " time-last-checked"
Set the time the filesystem was last checked using
.BR 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
of
.I time-last-checked
is the international date format, with an optional time specifier, i.e.
-YYYYMMDD[[HHMM]SS]. The keyword
+YYYYMMDD[HH[MM[SS]]]. The keyword
.B now
is also accepted, in which case the last checked time will be set to the
current time.
We haven't found any bugs yet. That doesn't mean there aren't any...
.SH AUTHOR
.B tune2fs
-was written by Remy Card <Remy.Card@linux.org>.
+was written by Remy Card <Remy.Card@linux.org>. It is currently being
+maintained by Theodore Ts'o <tytso@alum.mit.edu>.
.B 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>.
is part of the e2fsprogs package and is available from
http://e2fsprogs.sourceforge.net.
.SH SEE ALSO
+.BR debugfs (8),
.BR dumpe2fs (8),
.BR e2fsck (8),
.BR mke2fs (8)
git://git.whamcloud.com / tools / e2fsprogs.git / blobdiff