projects / thirdparty / e2fsprogs.git / blame
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|---|---|---|
| 4836459a TT |
1 | .TH E4DEFRAG 8 "May 2009" "e4defrag version 2.0" |
| 2 | .SH NAME | |
| 3 | e4defrag \- online defragmenter for ext4 filesystem | |
| 4 | .SH SYNOPSIS | |
| 5 | .B e4defrag | |
| 6 | [ | |
| 7 | .B \-c | |
| 8 | ] | |
| 9 | [ | |
| 10 | .B \-v | |
| 11 | ] | |
| 12 | .I target | |
| 13 | \&... | |
| 14 | .SH DESCRIPTION | |
| 15 | .B e4defrag | |
| 16 | reduces fragmentation of extent based file. The file targeted by | |
| 17 | .B e4defrag | |
| 18 | is created on ext4 filesystem made with "-O extent" option (see | |
| 19 | .BR mke2fs (8)). | |
| 20 | The targeted file gets more contiguous blocks and improves the file access | |
| 21 | speed. | |
| 22 | .PP | |
| 23 | .I target | |
| 24 | is a regular file, a directory, or a device that is mounted as ext4 filesystem. | |
| 25 | If | |
| 26 | .I target | |
| 27 | is a directory, | |
| 28 | .B e4defrag | |
| 29 | reduces fragmentation of all files in it. If | |
| 30 | .I target | |
| 31 | is a device, | |
| 32 | .B e4defrag | |
| 33 | gets the mount point of it and reduces fragmentation of all files in this mount | |
| 34 | point. | |
| 35 | .SH OPTIONS | |
| 36 | .TP | |
| 37 | .B \-c | |
| 77e72e2b KM |
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 | |
| 4836459a TT |
41 | .B e4defrag |
| 42 | to | |
| 43 | .IR target . | |
| 44 | When used with | |
| 45 | .B \-v | |
| 77e72e2b KM |
46 | option, the current fragmentation count and the ideal fragmentation count are |
| 47 | printed for each file. | |
| 48 | .IP | |
| 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 filesystem (if block size is 4KB). | |
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52 | .IP |
| 53 | If this option is specified, | |
| 54 | .I target | |
| 55 | is never defragmented. | |
| 56 | .TP | |
| 57 | .B \-v | |
| 58 | Print error messages and the fragmentation count before and after defrag for | |
| 59 | each file. | |
| 60 | .SH NOTES | |
| 61 | .B e4defrag | |
| 62 | does not support swap file, files in lost+found directory, and files allocated | |
| 63 | in indirect blocks. When | |
| 64 | .I target | |
| 65 | is a device or a mount point, | |
| 66 | .B e4defrag | |
| 67 | doesn't defragment files in mount point of other device. | |
| 68 | .PP | |
| 97b7a946 TT |
69 | It 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 | |
| 73 | bandwidth. | |
| 74 | .PP | |
| 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. | |
| 78 | .PP | |
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79 | Non-privileged users can execute |
| 80 | .B e4defrag | |
| 81 | to their own file, but the score is not printed if | |
| 82 | .B \-c | |
| 83 | option is specified. Therefore, it is desirable to be executed by root user. | |
| 84 | .SH AUTHOR | |
| 85 | Written by Akira Fujita <a-fujita@rs.jp.nec.com> and Takashi Sato | |
| 86 | <t-sato@yk.jp.nec.com>. | |
| 87 | .SH SEE ALSO | |
| 88 | .BR mke2fs (8), | |
| 89 | .BR mount (8). | |
| 90 |