.\"
.TH TUNE2FS 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
.SH NAME
-tune2fs \- adjust tunable filesystem parameters on ext2/ext3 filesystems
+tune2fs \- adjust tunable filesystem parameters on ext2/ext3/ext4 filesystems
.SH SYNOPSIS
.B tune2fs
[
.SH DESCRIPTION
.BI tune2fs
allows the system administrator to adjust various tunable filesystem
-parameters on Linux ext2/ext3 filesystems.
+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.
+.PP
+The
+.I device
+specifer can either be a filename (i.e., /dev/sda1), or a LABEL or UUID
+specifer: "\fBLABEL=\fIvolume-name\fR" or "\fBUUID=\fIuuid\fR". (i.e.,
+LABEL=home or UUID=e40486c6-84d5-4f2f-b99c-032281799c9d).
.SH OPTIONS
.TP
.BI \-c " max-mount-counts"
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 performanace.
+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
+.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
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
+.BI 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
+.B -o
+option,
+.I mount_option_string
+is an arbitrary string with a maximum length of 63 bytes, which is
+stored in the superblock.
+.IP
+The ext4 file system driver will first apply
+the bitmask-based default options, and then parse the
+.IR mount_option_string ,
+before parsing the mount options passed from the
+.BR mount (8)
+program.
+.IP
+This superblock setting is only honored in 2.6.35+ kernels;
+and not at all by the ext2 and ext3 file system drivers.
+.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 \-i " \fIinterval-between-checks\fR[\fBd\fR|\fBm\fR|\fBw\fR]"
Adjust the maximal time between two filesystem checks.
-No postfix or
+No suffix or
.B d
-result in days,
+will interpret the number
+.I interval-between-checks
+as days,
.B m
-in months, and
+as months, and
.B w
-in weeks. A value of zero will disable the time-dependent checking.
+as weeks. A value of zero will disable the time-dependent checking.
.sp
It is strongly recommended that either
.B \-c
@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.
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.
+.TP
+.B 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.)
+.TP
+.B 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.)
+.TP
+.B discard
+The file system will be mouinted 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.)
+.TP
+.B 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.)
.RE
.TP
.BR \-O " [^]\fIfeature\fR[,...]"
.BR tune2fs :
.RS 1.2i
.TP
-.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.
.TP
+.B flex_bg
+Allow bitmaps and inode tables for a block group to be placed
+anywhere on the storage media. \fBTune2fs\fR will not reorganize
+the location of the inode tables and allocation bitmaps, as
+.BR mke2fs (8)
+will do when it creates a freshly formated file system with
+.B flex_bg
+enabled.
+.TP
.B has_journal
Use a journal to ensure filesystem consistency even across unclean shutdowns.
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.
+.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 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 sparse_super
+Limit the number of backup superblocks to save space on large filesystems.
+.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
.BR sparse_super ,
+.BR uninit_bg ,
.BR filetype ,
or
.B resize_inode
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.
-.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
git://git.whamcloud.com / tools / e2fsprogs.git / blobdiff