e4defrag <root
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 cre‐
       ated on ext4 filesystem 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 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.

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  frag‐
              mentation 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  and Takashi Sato .

SEE ALSO
       mke2fs(8), mount(8).

e4defrag version 2.0                         May 2009                                 E4DEFRAG(8)

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