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To improve consistency, use "file system" in all of the man pages in preference over "filesystem". Signed-off-by: Theodore Ts'o <tytso@mit.edu>
91 lines
2.5 KiB
Groff
91 lines
2.5 KiB
Groff
.TH E4DEFRAG 8 "May 2009" "e4defrag version 2.0"
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.SH NAME
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e4defrag \- online defragmenter for ext4 file system
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.SH SYNOPSIS
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.B e4defrag
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[
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.B \-c
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]
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[
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.B \-v
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]
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.I target
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\&...
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.SH DESCRIPTION
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.B e4defrag
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reduces fragmentation of extent based file. The file targeted by
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.B e4defrag
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is created on ext4 file system made with "-O extent" option (see
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.BR mke2fs (8)).
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The targeted file gets more contiguous blocks and improves the file access
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speed.
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.PP
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.I target
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is a regular file, a directory, or a device that is mounted as ext4 file system.
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If
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.I target
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is a directory,
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.B e4defrag
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reduces fragmentation of all files in it. If
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.I target
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is a device,
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.B e4defrag
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gets the mount point of it and reduces fragmentation of all files in this mount
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point.
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.SH OPTIONS
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.TP
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.B \-c
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Get a current fragmentation count and an ideal fragmentation count, and
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calculate fragmentation score based on them. By seeing this score, we can
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determine whether we should execute
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.B e4defrag
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to
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.IR target .
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When used with
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.B \-v
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option, the current fragmentation count and the ideal fragmentation count are
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printed for each file.
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.IP
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Also this option outputs the average data size in one extent. If you see it,
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you'll find the file has ideal extents or not. Note that the maximum extent
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size is 131072KB in ext4 file system (if block size is 4KB).
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.IP
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If this option is specified,
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.I target
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is never defragmented.
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.TP
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.B \-v
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Print error messages and the fragmentation count before and after defrag for
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each file.
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.SH NOTES
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.B e4defrag
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does not support swap file, files in lost+found directory, and files allocated
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in indirect blocks. When
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.I target
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is a device or a mount point,
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.B e4defrag
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doesn't defragment files in mount point of other device.
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.PP
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It is safe to run e4defrag on a file while it is actively in use by another
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application. Since the contents of file blocks are copied using the
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page cache, this can result in a performance slowdown to both e4defrag
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and the application due to contention over the system's memory and disk
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bandwidth.
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.PP
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If the file system's free space is fragmented, or if there is
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insufficient free space available, e4defrag may not be able
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to improve the file's fragmentation.
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.PP
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Non-privileged users can execute
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.B e4defrag
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to their own file, but the score is not printed if
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.B \-c
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option is specified. Therefore, it is desirable to be executed by root user.
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.SH AUTHOR
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Written by Akira Fujita <a-fujita@rs.jp.nec.com> and Takashi Sato
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<t-sato@yk.jp.nec.com>.
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.SH SEE ALSO
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.BR mke2fs (8),
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.BR mount (8).
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