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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 file system
e4defrag [ -c ] [ -v ] target ...
e4defrag reduces fragmentation of extent based file. The file
targeted by e4defrag is created on ext4 file system 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 file system. 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 file system (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 is 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
2023-12-22. (At that time, the date of the most recent commit
that was found in the repository was 2023-12-07.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better 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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HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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