Provided by: e2fsprogs_1.43.4-2_amd64 bug

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 created 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
              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 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.

       It 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.

AUTHOR

       Written by Akira Fujita <a-fujita@rs.jp.nec.com> and Takashi  Sato  <t-
       sato@yk.jp.nec.com>.

SEE ALSO

       mke2fs(8), mount(8).