NAME
tunefs —
tune up an existing file
system
SYNOPSIS
tunefs |
[-AFN]
[-e
maxbpg]
[-g
avgfilesize]
[-h
avgfpdir]
[-l
logsize]
[-m
minfree]
[-o
optimize_preference]
[-q quota]
[-S
sectorsize] special |
filesys |
DESCRIPTION
tunefs is designed to change the dynamic parameters of a file
system which affect the layout policies.
The following options are supported by
tunefs:
-
-
- -A
- Cause the values to be updated in all the alternate
superblocks instead of just the standard superblock. If this option is not
used, then use of a backup superblock by
fsck(8) will lose anything
changed by tunefs. -A is ignored when
-N is specified.
-
-
- -F
- Indicates that special is a file
system image, rather than a device name or file system mount point.
special will be accessed ‘as-is’.
-
-
- -N
- Display all the settable options (after any changes from
the tuning options) but do not cause any of them to be changed.
-
-
- -e
maxbpg
- This indicates the maximum number of blocks any single file
can allocate out of a cylinder group before it is forced to begin
allocating blocks from another cylinder group. Typically this value is set
to about one quarter of the total blocks in a cylinder group. The intent
is to prevent any single file from using up all the blocks in a single
cylinder group, thus degrading access times for all files subsequently
allocated in that cylinder group. The effect of this limit is to cause big
files to do long seeks more frequently than if they were allowed to
allocate all the blocks in a cylinder group before seeking elsewhere. For
file systems with exclusively large files, this parameter should be set
higher.
-
-
- -g
avgfilesize
- This specifies the expected average file size.
-
-
- -h
avgfpdir
- This specifies the expected number of files per
directory.
-
-
- -l
logsize
- This value specifies the size of the in-filesystem
journaling log file. The default journaling log file size is described in
wapbl(4). Specifying a size
of zero will cause the in-filesystem journaling log file to be removed the
next time the filesystem is mounted. The size of an existing in-filesystem
journaling log file can not be changed directly. You need to first set the
log file size to zero, then mount the filesystem without logging enabled
(which will remove the log without creating a new one), unmount, set the
size to the new value and finally re-mount with logging enabled.
-
-
- -m
minfree
- This value specifies the percentage of space held back from
normal users; the minimum free space threshold. The default value is set
during creation of the filesystem, see
newfs(8). This value can be
set to zero, however up to a factor of three in throughput will be lost
over the performance obtained at a 5% threshold. Note that if the value is
raised above the current usage level, users will be unable to allocate
files until enough files have been deleted to get under the higher
threshold.
-
-
- -o
optimize_preference
- The file system can either try to minimize the time spent
allocating blocks, or it can attempt to minimize the space fragmentation
on the disk. If the value of minfree (see above) is less than 5%, then the
file system should optimize for space to avoid running out of full sized
blocks. For values of minfree greater than or equal to 5%, fragmentation
is unlikely to be problematical, and the file system can be optimized for
time.
optimize_preference can be specified as either
space
or time
.
-
-
- -q
quota
- enable or disable a quota. quota can
be one of
user
, group
,
nouser
or nogroup
to
enable or disable the specified quota type. Multiple -q
can be used to enable/disable all types at once.
After enabling a quota,
fsck_ffs(8) has to be run
to compute the correct quota values.
-
-
- -S
sectorsize
- changes the fsbtodb value in the superblock to reflect a
particular physical sector size. This value is ignored by the
NetBSD kernel but needed by tools like
fsck_ffs(8) to access disk
blocks correctly. The minimum value is
DEV_BSIZE
(512).
Changing the fsbtodb value becomes necessary when a filesystem image is
created for one sector size and then transferred to a device with a
different sector size and should be applied also to the alternate
superblocks.
SEE ALSO
wapbl(4),
fs(5),
dumpfs(8),
fsck_ffs(8),
newfs(8)
M. McKusick, W.
Joy, S. Leffler, and R.
Fabry, A Fast File System for UNIX,
ACM Transactions on Computer Systems 2,
3, pp 181-197,
August 1984, (reprinted in the BSD
System Manager's Manual, SMM:5).
HISTORY
The
tunefs command appeared in
4.2BSD.
BUGS
This program should work on mounted and active file systems. Because the
super-block is not kept in the buffer cache, the changes will only take effect
if the program is run on unmounted file systems. To change the root file
system, the system must be rebooted after the file system is tuned.
You can tune a file system, but you can't tune a fish.