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1 | .\" -*- nroff -*- |
2 | .\" Copyright 2001 by Theodore Ts'o. All Rights Reserved. | |
3 | .\" This file may be copied under the terms of the GNU Public License. | |
4 | .\" | |
5 | .TH E2IMAGE 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@" | |
6 | .SH NAME | |
a7ac1df3 | 7 | e2image \- Save critical ext2/ext3 filesystem data to a file |
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8 | .SH SYNOPSIS |
9 | .B e2image | |
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10 | [ |
11 | .B \-r | |
12 | ] | |
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13 | .I device |
14 | .I image-file | |
15 | .SH DESCRIPTION | |
0edb4d85 | 16 | The |
348e43dc | 17 | .B e2image |
0edb4d85 | 18 | program will save critical filesystem data on the ext2 filesystem located on |
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19 | .I device |
20 | to a file specified by | |
21 | .IR image-file . | |
22 | The image file may be examined by | |
23 | .B dumpe2fs | |
24 | and | |
25 | .BR debugfs , | |
26 | by using the | |
27 | .B \-i | |
28 | option to those programs. This can be used by an expert in assisting | |
29 | the recovery of catastrophically corrupted filesystems. In the future, | |
30 | e2fsck will be enhanced to be able to use the image file to help | |
31 | recover a badly damaged filesystem. | |
32 | .PP | |
1c1e0049 TT |
33 | If |
34 | .I image-file | |
35 | is -, then the output of | |
36 | .B e2image | |
8ac59297 TT |
37 | will be sent to standard output, so that the output can be piped to |
38 | another program, such as | |
39 | .BR gzip (1). | |
40 | (Note that is currently only supported when | |
41 | creating a raw image file using the | |
42 | .B \-r | |
43 | option, since the process of creating a normal image file currently | |
44 | requires random-access access to the file, which can not be done using a | |
45 | pipe. This restriction will hopefully be lifted in a future version of | |
46 | .BR e2image .) | |
1c1e0049 | 47 | .PP |
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48 | The |
49 | .B \-r | |
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50 | option will create a raw image file instead of a normal image file. |
51 | A raw image file differs | |
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52 | from a normal image file in two ways. First, the filesystem metadata is |
53 | placed in the proper position so that e2fsck, dumpe2fs, debugfs, | |
54 | etc. can be run directly on the raw image file. In order to minimize | |
55 | the amount of disk space consumed by a raw image file, the file is | |
56 | created as a sparse file. (Beware of copying or | |
57 | compressing/decompressing this file with utilities that don't understand | |
58 | how to create sparse files; the file will become as large as the | |
59 | filesystem itself!) Secondly, the raw image file also includes indirect | |
1c1e0049 | 60 | blocks and data blocks, which the current image file does not have, |
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61 | although this may change in the future. |
62 | .PP | |
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63 | It is a very good idea to periodically (at boot time and |
64 | every week or so) to create image files for all of | |
65 | filesystems on a system, as well as saving the partition | |
66 | layout (which can be generated using the using | |
67 | .B fdisk -l | |
68 | command). Ideally the image file should be stored on some filesystem | |
69 | other that | |
70 | the filesystem whose data it contains, to ensure that its data is | |
71 | accessible in the case where the filesystem has been badly damaged. | |
72 | .PP | |
73 | To save disk space, | |
74 | .B e2image | |
75 | creates the image file as a sparse file. | |
76 | Hence, if the image file | |
77 | needs to be copied to another location, it should | |
78 | either be compressed first or copied using the | |
79 | .B \--sparse=always | |
80 | option to GNU version of | |
81 | .BR cp . | |
82 | .PP | |
83 | The size of an ext2 image file depends primarily on the size of the | |
84 | filesystems and how many inodes are in use. For a typical 10 gigabyte | |
85 | filesystem, with 200,000 inodes in use out of 1.2 million inodes, the | |
86 | image file be approximately 35 megabytes; a 4 gigabyte filesystem with | |
87 | 15,000 inodes in use out of 550,000 inodes will result in a 3 megabyte | |
88 | image file. Image files tend to be quite | |
6304baf2 | 89 | compressible; an image file taking up 32 megabytes of space on |
0edb4d85 | 90 | disk will generally compress down to 3 or 4 megabytes. |
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91 | .PP |
92 | .SH AUTHOR | |
0edb4d85 | 93 | .B e2image |
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94 | was written by Theodore Ts'o (tytso@mit.edu). |
95 | .SH AVAILABILITY | |
96 | .B e2image | |
97 | is part of the e2fsprogs package and is available from anonymous | |
98 | http://e2fsprogs.sourceforge.net. | |
99 | .SH SEE ALSO | |
100 | .BR dumpe2fs (8), | |
101 | .BR debugfs (8) | |
102 |