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   e4defrag    ( 8 )

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Имя (Name)

e4defrag - online defragmenter for ext4 file system

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Синопсис (Synopsis)

e4defrag [ -c ] [ -v ] target ...

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Описание (Description)

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.

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Параметры (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 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.

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Примечание (Note)

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.

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