e2fsprogs/misc/tune2fs.8.in

.\" Revision 1.0 93/06/3 23:00  chk
.\" Initial revision
.\"
.\"
.TH TUNE2FS 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
.SH NAME
tune2fs \- adjust tunable filesystem parameters on second extended filesystems
.SH SYNOPSIS
.B tune2fs
[
.B \-l
]
[
.B \-c
.I max-mount-counts
]
[
.B \-e
.I errors-behavior
]
[
.B \-i
.I interval-between-checks
]
[
.B \-j
]
[
.B \-J
.I journal-options
]
[
.B \-m
.I reserved-blocks-percentage
]
[
.B \-r
.I reserved-blocks-count
]
[
.B \-s
.I sparse-super-flag
]
[
.B \-u
.I user
]
[
.B \-g
.I group
]
[
.B \-C
.I mount-count
]
[
.B \-L
.I volume-name
]
[
.B \-M
.I last-mounted-directory
]
[
.B \-O 
.RI [^] feature [,...]
]
[
.B \-U
.I UUID
]
device
.SH DESCRIPTION
.BI tune2fs
adjusts tunable filesystem parameters on a Linux second extended filesystem.
.SH OPTIONS
.TP
.BI \-c " max-mount-counts"
Adjust the maximal mounts count between two filesystem checks.  If 
.I max-mount-counts
is 0 then the number of times the filesystem is mounted will be disregarded
by
.BR e2fsck (8)
and the kernel.
.sp
Staggering the mount-counts at which filesystems are forcibly
checked will avoid all filesystems being checked at one time
when using journaled filesystems.
.sp
You should strongly 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
.B 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.
.sp
See also the
.B \-i
option for time-dependent checking.
.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.
.TP
.BI \-e " error-behavior"
Change the behavior of the kernel code when errors are detected.
In all cases, a filesystem error will cause
.BR e2fsck (8)
to check the filesystem on the next boot.
.I error-behavior
can be one of the following:
.RS 1.2i
.TP 1.2i
.B continue
Continue normal execution.
.TP
.B remount-ro
Remount filesystem read-only.
.TP
.B panic
Cause a kernel panic.
.RE
.TP
.BI \-g " group"
Set the group which can use reserved filesystem blocks.
The 
.I 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.
.TP
.B \-i " \fIinterval-between-checks\fR[\fBd\fR|\fBm\fR|\fBw\fR]"
Adjust the maximal time between two filesystem checks. 
No postfix or
.B d
result in days,
.B m
in months, and
.B w
in weeks.  A value of zero will disable the time-dependent checking.
.sp
It is strongly recommended that either
.B \-c
(mount-count-dependent) or
.B \-i
(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.
.TP
.B \-j
Add an ext3 journal to the filesystem.  If the 
.B \-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.
.TP
.BR \-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:
.RS 1.2i
.TP
.BI size= journal-size
Create a journal stored in the filesystem of size
.I 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 102,400 filesystem blocks.
There must be enough free space in the filesystem to create a journal of
that size.
@JDEV@.TP
@JDEV@.BI device= external-journal
@JDEV@Attach the filesystem to the journal block device located on
@JDEV@.IR external-journal .
@JDEV@to the filesystem.
@JDEV@The external 
@JDEV@journal must have been already created using the command
@JDEV@.IP
@JDEV@.B mke2fs -O journal_dev 
@JDEV@.IR external-journal.
@JDEV@.IP
@JDEV@Note that
@JDEV@.I external-journal
@JDEV@must be formatted with the same block
@JDEV@size as filesystems which will be using it.
.RE
@JDEV@.IP
@JDEV@Only one of the
@JDEV@.BR size " or " device
@JDEV@options can be given for a filesystem.
.TP
.B \-l
List the contents of the filesystem superblock.
.TP
.BI \-L " volume-label"
Set the volume label of the filesystem.  
Ext2 filesystem labels can be at most 16 characters long; if
.I volume-label 
is longer than 16 characters, 
.B tune2fs
will truncate it and print a warning.  
.TP
.BI \-m " reserved-blocks-percentage"
Set the percentage of reserved filesystem blocks.
.TP
.BI \-M " last-mounted-directory"
Set the last-mounted directory for the filesystem.
.TP
.BR \-O " [^]\fIfeature\fR[,...]"
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.
.IP
The following filesystem features can be set or cleared using
.BR tune2fs :
.RS 1.2i
.TP
.B sparse_super
Limit the number of backup superblocks to save space on large filesystems.
.TP
.B filetype
Store file type information in directory entries.
.TP
.B has_journal
Create an ext3 journal (as if using the
.B \-j
option).
.RE
.IP
After setting or clearing any filesystem feature,
.BR e2fsck (8)
must be run on the filesystem to return the filesystem to a consistent state.
.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.
.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 \-u " user"
Set the user who can use the reserved filesystem blocks.
.I 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.
.TP
.BI \-U " UUID"
Set the universally unique identifier (UUID) of the filesystem to
.IR UUID .
The format of the UUID is a series of hex digits separated by hypthens, 
like this: 
"c1b9d5a2-f162-11cf-9ece-0020afc76f16".  
The 
.I UUID
parameter may also be one of the following:
.RS 1.2i
.TP
.I clear
clear the filesystem UUID
.TP
.I random
generate a new randomly-generated UUID
.TP
.I time
generate a new time-based UUID
.RE
.IP
See
.BR uuidgen (8)
for more information.
If the system does not have a good random number generator such as
.I /dev/random
or
.IR /dev/urandom ,
.B tune2fs
will automatically use a time-based UUID instead of a randomly-generated UUID.
.SH BUGS
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>.
.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>.
Time-dependent checking was added by Uwe Ohse <uwe@tirka.gun.de>.
.SH AVAILABILITY
.B tune2fs
is part of the e2fsprogs package and is available from 
http://e2fsprogs.sourceforge.net.
.SH SEE ALSO
.BR dumpe2fs (8),
.BR e2fsck (8),
.BR mke2fs (8)