E4DEFRAG(8) System Manager's Manual E4DEFRAG(8)
NAME
e4defrag - online defragmenter for ext4 filesystem
SYNOPSIS
e4defrag [ -c ] [ -v ] target ...
DESCRIPTION
e4defrag reduces fragmentation of extent based file. The file targeted by e4defrag is created on ext4 filesys‐
tem 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 direc‐
tory, 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.
OPTIONS
-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.
NOTES
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.
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.
AUTHOR
Written by Akira Fujita <[email protected]> and Takashi Sato <[email protected]>.
SEE ALSO
mke2fs(8), mount(8).
e4defrag version 2.0 May 2009 E4DEFRAG(8)
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