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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | NOTES | AUTHOR | SEE ALSO | COLOPHON |
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E4DEFRAG(8) System Manager's Manual E4DEFRAG(8)
e4defrag - online defragmenter for ext4 filesystem
e4defrag [ -c ] [ -v ] target ...
e4defrag reduces fragmentation of extent based file. The file
targeted by e4defrag is created on ext4 filesystem made with "-O
extent" option (see mke2fs(8)). The targeted file gets more
contiguous blocks and improves the file access speed.
target is a regular file, a directory, or a device that is mounted as
ext4 filesystem. If target is a directory, e4defrag reduces
fragmentation of all files in it. If target is a device, e4defrag
gets the mount point of it and reduces fragmentation of all files in
this mount point.
-c Get a current fragmentation count and an ideal fragmentation
count, and calculate fragmentation score based on them. By
seeing this score, we can determine whether we should execute
e4defrag to target. When used with -v option, the current
fragmentation count and the ideal fragmentation count are
printed for each file.
Also this option outputs the average data size in one extent.
If you see it, you'll find the file has ideal extents or not.
Note that the maximum extent size is 131072KB in ext4
filesystem (if block size is 4KB).
If this option is specified, target is never defragmented.
-v Print error messages and the fragmentation count before and
after defrag for each file.
e4defrag does not support swap file, files in lost+found directory,
and files allocated in indirect blocks. When target is a device or a
mount point, e4defrag doesn't defragment files in mount point of
other device.
It safe to run e4defrag on a file while it is actively in use by
another application. Since the contents of file blocks are copied
using the page cache, this can result in a performance slowdown to
both e4defrag and the application due to contention over the system's
memory and disk bandwidth.
If the file system's free space is fragmented, or if there is
insufficient free space available, e4defrag may not be able to
improve the file's fragmentation.
Non-privileged users can execute e4defrag to their own file, but the
score is not printed if -c option is specified. Therefore, it is
desirable to be executed by root user.
Written by Akira Fujita <a-fujita@rs.jp.nec.com> and Takashi Sato <t-
sato@yk.jp.nec.com>.
mke2fs(8), mount(8).
This page is part of the e2fsprogs (utilities for ext2/3/4
filesystems) project. Information about the project can be found at
⟨http://e2fsprogs.sourceforge.net/⟩. It is not known how to report
bugs for this man page; if you know, please send a mail to
man-pages@man7.org. This page was obtained from the project's
upstream Git repository
⟨git://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git⟩ on 2018-02-02.
(At that time, the date of the most recent commit that was found in
the repository was 2018-01-03.) If you discover any rendering prob‐
lems in this HTML version of the page, or you believe there is a bet‐
ter or more up-to-date source for the page, or you have corrections
or improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to man-pages@man7.org
e4defrag version 2.0 May 2009 E4DEFRAG(8)
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