1 .TH E4DEFRAG 8 "May 2009" "e4defrag version 2.0"
3 e4defrag \- online defragmenter for ext4 file system
16 reduces fragmentation of extent based file. The file targeted by
18 is created on ext4 file system made with "-O extent" option (see
20 The targeted file gets more contiguous blocks and improves the file access
24 is a regular file, a directory, or a device that is mounted as ext4 file system.
29 reduces fragmentation of all files in it. If
33 gets the mount point of it and reduces fragmentation of all files in this mount
38 Get a current fragmentation count and an ideal fragmentation count, and
39 calculate fragmentation score based on them. By seeing this score, we can
40 determine whether we should execute
46 option, the current fragmentation count and the ideal fragmentation count are
47 printed for each file.
49 Also this option outputs the average data size in one extent. If you see it,
50 you'll find the file has ideal extents or not. Note that the maximum extent
51 size is 131072KB in ext4 file system (if block size is 4KB).
53 If this option is specified,
55 is never defragmented.
58 Print error messages and the fragmentation count before and after defrag for
62 does not support swap file, files in lost+found directory, and files allocated
63 in indirect blocks. When
65 is a device or a mount point,
67 doesn't defragment files in mount point of other device.
69 It is safe to run e4defrag on a file while it is actively in use by another
70 application. Since the contents of file blocks are copied using the
71 page cache, this can result in a performance slowdown to both e4defrag
72 and the application due to contention over the system's memory and disk
75 If the file system's free space is fragmented, or if there is
76 insufficient free space available, e4defrag may not be able
77 to improve the file's fragmentation.
79 Non-privileged users can execute
81 to their own file, but the score is not printed if
83 option is specified. Therefore, it is desirable to be executed by root user.
85 Written by Akira Fujita <a-fujita@rs.jp.nec.com> and Takashi Sato
86 <t-sato@yk.jp.nec.com>.