| .TH E4DEFRAG 8 "May 2009" "e4defrag version 2.0" |
| .SH NAME |
| e4defrag \- online defragmenter for ext4 filesystem |
| .SH SYNOPSIS |
| .B e4defrag |
| [ |
| .B \-c |
| ] |
| [ |
| .B \-v |
| ] |
| .I target |
| \&... |
| .SH DESCRIPTION |
| .B e4defrag |
| reduces fragmentation of extent based file. The file targeted by |
| .B e4defrag |
| is created on ext4 filesystem made with "-O extent" option (see |
| .BR mke2fs (8)). |
| The targeted file gets more contiguous blocks and improves the file access |
| speed. |
| .PP |
| .I target |
| is a regular file, a directory, or a device that is mounted as ext4 filesystem. |
| If |
| .I target |
| is a directory, |
| .B e4defrag |
| reduces fragmentation of all files in it. If |
| .I target |
| is a device, |
| .B e4defrag |
| gets the mount point of it and reduces fragmentation of all files in this mount |
| point. |
| .SH OPTIONS |
| .TP |
| .B \-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 |
| .B e4defrag |
| to |
| .IR target . |
| When used with |
| .B \-v |
| option, the current fragmentation count and the ideal fragmentation count are |
| printed for each file. |
| .IP |
| 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). |
| .IP |
| If this option is specified, |
| .I target |
| is never defragmented. |
| .TP |
| .B \-v |
| Print error messages and the fragmentation count before and after defrag for |
| each file. |
| .SH NOTES |
| .B e4defrag |
| does not support swap file, files in lost+found directory, and files allocated |
| in indirect blocks. When |
| .I target |
| is a device or a mount point, |
| .B e4defrag |
| doesn't defragment files in mount point of other device. |
| .PP |
| 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. |
| .PP |
| 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. |
| .PP |
| Non-privileged users can execute |
| .B e4defrag |
| to their own file, but the score is not printed if |
| .B \-c |
| option is specified. Therefore, it is desirable to be executed by root user. |
| .SH AUTHOR |
| Written by Akira Fujita <a-fujita@rs.jp.nec.com> and Takashi Sato |
| <t-sato@yk.jp.nec.com>. |
| .SH SEE ALSO |
| .BR mke2fs (8), |
| .BR mount (8). |
| |
