TUNE2FS(S) TUNE2FS(S) NAME tune2fs - adjust tunable filesystem parameters on second extended filesystems SYNOPSIS tune2fs [ -l ] [ -c max-mount-counts ] [ -e errors-behav- ior ] [ -f ] [ -i interval-between-checks ] [ -j ] [ -J journal-options ] [ -m reserved-blocks-percentage ] [ -r reserved-blocks-count ] [ -s sparse-super-flag ] [ -u user ] [ -g group ] [ -C mount-count ] [ -L volume-name ] [ -M last-mounted-directory ] [ -O [^]feature[,...] ] [ -T time-last-checked ] [ -U UUID ] device DESCRIPTION tune2fs adjusts tunable filesystem parameters on a Linux second extended filesystem. OPTIONS -c max-mount-counts Adjust the maximal mounts count between two filesystem checks. If max-mount-counts is 0 then the number of times the filesystem is mounted will be disregarded by e2fsck(k) 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. 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 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. Can be used in conjunction with -c to force an fsck on 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(k) to check the filesystem on the next boot. error-behavior can be one of the fol- lowing: continue Continue normal execution. remount-ro Remount filesystem read-only. panic Cause a kernel panic. -f Force the tune2fs operation to complete even in the face of errors. This option is useful when remov- ing 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 avail- able. 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 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 postfix or d result in days, m in months, and w in weeks. A value of zero will dis- able the time-dependent checking. It is strongly recommended that either -c (mount- count-dependent) or -i (time-dependent) checking be enabled to force periodic full e2fsck(k) 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. -j Add an ext3 journal to the filesystem. If the -J option is not specified, the default journal param- eters 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 actu- ally make use of the journal. -J journal-options Override the default ext3 journal parameters. Jour- nal options are comma separated, and may take an argument using the equals ('=') sign. The follow- ing journal options are supported: size=journal-size Create a journal stored in the filesys- tem 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 102,400 filesystem blocks. There must be enough free space in the filesystem to create a journal of that size. device=external-journal Attach the filesystem to the journal block device located on external-jour- nal. The external journal must have been already created using the command mke2fs -O journal_dev external-journal Note that external-journal must be for- matted with the same block size as filesystems which will be using it. Instead of specifying a device name directly, external-journal can also be specified by either LABEL=label or UUID=UUID to locate the external jour- nal by either the volume label or UUID stored in the ext2 superblock at the start of the journal. Use dumpe2fs(s) to display a journal device's volume label and UUID. See also the -L option of tune2fs(s). Only one of the size or device options can be given for a filesystem. -l List the contents of the filesystem superblock. -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(t), fsck(k), and /etc/fstab(b) (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 reserved filesystem blocks. -M last-mounted-directory Set the last-mounted directory for the filesystem. -O [^]feature[,...] Set or clear the indicated filesystem features (options) in the filesystem. More than one filesystem feature can be cleared or set by sepa- rating 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. The following filesystem features can be set or cleared using tune2fs: sparse_super Limit the number of backup superblocks to save space on large filesystems. filetype Store file type information in direc- tory entries. has_journal Create an ext3 journal (as if using the -j option). After setting or clearing sparse_super and filetype filesystem features, e2fsck(k) must be run on the filesystem to return the filesystem to a consistent state. Tune2fs will print a message requesting that the system administrator run e2fsck(k) if nec- essary. 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. -r reserved-blocks-count Set the number of reserved filesystem blocks. -s [0|1] Turn the sparse super feature off or on. Turning this feature on saves space on really big filesys- tems. This is the same as using the -O sparse_super option. 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 e2fsck(k) on the filesystem after changing this feature in order to have a valid filesystem. -T time-last-checked Set the time the filesystem was last checked using e2fsck. This can be useful in scripts which use a Logical Volume Manager to make a consistent snap- shot of a filesystem, and then check the filesystem during off hours to make sure it hasn't been cor- rupted 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[[HHMM]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 hypthens, 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(t), fsck(k), and /etc/fstab(b) (and possibly others) by specifying UUID=uuid instead of a block special device name like /dev/hda1. See uuidgen(n) for more information. If the system does not have a good random number generator such as /dev/random or /dev/urandom, tune2fs will auto- matically use a time-based UUID instead of a ran- domly-generated UUID. BUGS We haven't found any bugs yet. That doesn't mean there aren't any... AUTHOR tune2fs was written by Remy Card <Remy.Card@linux.org>. tune2fs uses the ext2fs library written by Theodore Ts'o <tytso@mit.edu>. This manual page was written by Chris- tian Kuhtz <chk@data-hh.Hanse.DE>. Time-dependent check- ing was added by Uwe Ohse <uwe@tirka.gun.de>. AVAILABILITY tune2fs is part of the e2fsprogs package and is available from http://e2fsprogs.sourceforge.net. SEE ALSO dumpe2fs(s), e2fsck(k), mke2fs(s) E2fsprogs version 1.27 March 2002 TUNE2FS(S)