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94 lines
3.1 KiB
Groff
94 lines
3.1 KiB
Groff
.\" -*- nroff -*-
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.\" Copyright 2001 by Theodore Ts'o. All Rights Reserved.
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.\" This file may be copied under the terms of the GNU Public License.
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.\"
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.TH E2IMAGE 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
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.SH NAME
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e2image \- Save critical ext2 filesystem data to a file
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.SH SYNOPSIS
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.B e2image
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[
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.B \-r
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]
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.I device
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.I image-file
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.SH DESCRIPTION
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The
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.B e2image
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program will save critical filesystem data on the ext2 filesystem located on
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.I device
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to a file specified by
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.IR image-file .
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The image file may be examined by
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.B dumpe2fs
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and
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.BR debugfs ,
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by using the
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.B \-i
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option to those programs. This can be used by an expert in assisting
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the recovery of catastrophically corrupted filesystems. In the future,
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e2fsck will be enhanced to be able to use the image file to help
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recover a badly damaged filesystem.
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.PP
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If
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.I image-file
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is -, then the output of
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.B e2image
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will be sent to standard output.
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.PP
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The
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.B \-r
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option will create a raw image file instead of a normal image file.
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A raw image file differs
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from a normal image file in two ways. First, the filesystem metadata is
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placed in the proper position so that e2fsck, dumpe2fs, debugfs,
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etc. can be run directly on the raw image file. In order to minimize
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the amount of disk space consumed by a raw image file, the file is
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created as a sparse file. (Beware of copying or
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compressing/decompressing this file with utilities that don't understand
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how to create sparse files; the file will become as large as the
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filesystem itself!) Secondly, the raw image file also includes indirect
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blocks and data blocks, which the current image file does not have,
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although this may change in the future.
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.PP
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It is a very good idea to periodically (at boot time and
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every week or so) to create image files for all of
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filesystems on a system, as well as saving the partition
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layout (which can be generated using the using
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.B fdisk -l
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command). Ideally the image file should be stored on some filesystem
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other that
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the filesystem whose data it contains, to ensure that its data is
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accessible in the case where the filesystem has been badly damaged.
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.PP
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To save disk space,
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.B e2image
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creates the image file as a sparse file.
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Hence, if the image file
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needs to be copied to another location, it should
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either be compressed first or copied using the
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.B \--sparse=always
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option to GNU version of
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.BR cp .
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.PP
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The size of an ext2 image file depends primarily on the size of the
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filesystems and how many inodes are in use. For a typical 10 gigabyte
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filesystem, with 200,000 inodes in use out of 1.2 million inodes, the
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image file be approximately 35 megabytes; a 4 gigabyte filesystem with
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15,000 inodes in use out of 550,000 inodes will result in a 3 megabyte
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image file. Image files tend to be quite
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compressible; an image file taking up 32 megabytes of space on
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disk will generally compress down to 3 or 4 megabytes.
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.PP
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.SH AUTHOR
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.B e2image
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was written by Theodore Ts'o (tytso@mit.edu).
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.SH AVAILABILITY
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.B e2image
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is part of the e2fsprogs package and is available from anonymous
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http://e2fsprogs.sourceforge.net.
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.SH SEE ALSO
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.BR dumpe2fs (8),
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.BR debugfs (8)
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