1E2IMAGE(8) System Manager's Manual E2IMAGE(8)
2
6 e2image - Save critical ext2/ext3/ext4 filesystem metadata to a file
7
9 e2image [ -r|-Q ] [ -f ] [ -b superblock ] [ -B blocksize ] device
10 image-file
11 e2image -I device image-file
12 e2image -ra [ -cfnp ] [ -o src_offset ] [ -O dest_offset ] src_fs [
13 dest_fs ]
14
16 The e2image program will save critical ext2, ext3, or ext4 filesystem
17 metadata located on device to a file specified by image-file. The
18 image file may be examined by dumpe2fs and debugfs, by using the -i
19 option to those programs. This can assist an expert in recovering cat‐
20 astrophically corrupted filesystems. In the future, e2fsck will be
21 enhanced to be able to use the image file to help recover a badly dam‐
22 aged filesystem.
23 When saving an e2image for debugging purposes, using either the -r or
25 -Q options, the filesystem must be unmounted or be mounted read/only,
26 in order for the image file to be in a consistent state. This require‐
27 ment can be overridden using the -f option, but the resulting image
28 file is very likely not going to be useful.
29 If image-file is -, then the output of e2image will be sent to standard
31 output, so that the output can be piped to another program, such as
32 gzip(1). (Note that this is currently only supported when creating a
33 raw image file using the -r option, since the process of creating a
34 normal image file, or QCOW2 image currently requires random access to
35 the file, which cannot be done using a pipe. This restriction will
36 hopefully be lifted in a future version of e2image.)
37 It is a very good idea to create image files for all of filesystems on
39 a system and save the partition layout (which can be generated using
40 the fdisk -l command) at regular intervals --- at boot time, and/or
41 every week or so. The image file should be stored on some filesystem
42 other than the filesystem whose data it contains, to ensure that this
43 data is accessible in the case where the filesystem has been badly dam‐
44 aged.
45 To save disk space, e2image creates the image file as a sparse file, or
47 in QCOW2 format. Hence, if the sparse image file needs to be copied to
48 another location, it should either be compressed first or copied using
49 the --sparse=always option to the GNU version of cp. This does not
50 apply to the QCOW2 image, which is not sparse.
51 The size of an ext2 image file depends primarily on the size of the
53 filesystems and how many inodes are in use. For a typical 10 gigabyte
54 filesystem, with 200,000 inodes in use out of 1.2 million inodes, the
55 image file will be approximately 35 megabytes; a 4 gigabyte filesystem
56 with 15,000 inodes in use out of 550,000 inodes will result in a 3
57 megabyte image file. Image files tend to be quite compressible; an
58 image file taking up 32 megabytes of space on disk will generally com‐
59 press down to 3 or 4 megabytes.
60
62 The -I option will cause e2image to install the metadata stored in the
63 image file back to the device. It can be used to restore the filesys‐
64 tem metadata back to the device in emergency situations.
65 WARNING!!!! The -I option should only be used as a desperation measure
67 when other alternatives have failed. If the filesystem has changed
68 since the image file was created, data will be lost. In general, you
69 should make a full image backup of the filesystem first, in case you
70 wish to try other recovery strategies afterwards.
71
73 The -r option will create a raw image file instead of a normal image
74 file. A raw image file differs from a normal image file in two ways.
75 First, the filesystem metadata is placed in the proper position so that
76 e2fsck, dumpe2fs, debugfs, etc. can be run directly on the raw image
77 file. In order to minimize the amount of disk space consumed by a raw
78 image file, the file is created as a sparse file. (Beware of copying
79 or compressing/decompressing this file with utilities that don't under‐
80 stand how to create sparse files; the file will become as large as the
81 filesystem itself!) Secondly, the raw image file also includes indi‐
82 rect blocks and directory blocks, which the standard image file does
83 not have, although this may change in the future.
84 Raw image files are sometimes used when sending filesystems to the
86 maintainer as part of bug reports to e2fsprogs. When used in this
87 capacity, the recommended command is as follows (replace hda1 with the
88 appropriate device):
89 e2image -r /dev/hda1 - | bzip2 > hda1.e2i.bz2
91 This will only send the metadata information, without any data blocks.
93 However, the filenames in the directory blocks can still reveal infor‐
94 mation about the contents of the filesystem that the bug reporter may
95 wish to keep confidential. To address this concern, the -s option can
96 be specified. This will cause e2image to scramble directory entries
97 and zero out any unused portions of the directory blocks before writing
98 the image file. However, the -s option will prevent analysis of prob‐
99 lems related to hash-tree indexed directories.
100 Option -b superblock can be used to get image from partition with bro‐
102 ken primary superblock. The partition is copied as-is including broken
103 primary superblock.
104 Option -B blocksize can be used to set superblock block size. Normally,
106 e2fsck will search for the superblock at various different block sizes
107 in an attempt to find the appropriate blocksize. This search can be
108 fooled in some cases. This option forces e2fsck to only try locating
109 the superblock at a particular blocksize. If the superblock is not
110 found, e2fsck will terminate with a fatal error.
111 Note that this will work even if you substitute "/dev/hda1" for another
113 raw disk image, or QCOW2 image previously created by e2image.
114
116 The -Q option will create a QCOW2 image file instead of a normal, or
117 raw image file. A QCOW2 image contains all the information the raw
118 image does, however unlike the raw image it is not sparse. The QCOW2
119 image minimize the amount of disk space by storing data in special for‐
120 mat with pack data closely together, hence avoiding holes while still
121 minimizing size.
122 In order to send filesystem to the maintainer as a part of bug report
124 to e2fsprogs, use following commands (replace hda1 with the appropriate
125 device):
126 e2image -Q /dev/hda1 hda1.qcow2
128 bzip2 -z hda1.qcow2
129 This will only send the metadata information, without any data blocks.
131 However, the filenames in the directory blocks can still reveal infor‐
132 mation about the contents of the filesystem that the bug reporter may
133 wish to keep confidential. To address this concern, the -s option can
134 be specified. This will cause e2image to scramble directory entries
135 and zero out any unused portions of the directory blocks before writing
136 the image file. However, the -s option will prevent analysis of prob‐
137 lems related to hash-tree indexed directories.
138 Note that QCOW2 image created by e2image is regular QCOW2 image and can
140 be processed by tools aware of QCOW2 format such as for example qemu-
141 img.
142 You can convert a qcow2 image into a raw image with:
144 e2image -r hda1.qcow2 hda1.raw
146 This can be useful to write a qcow2 image containing all data to a
148 sparse image file where it can be loop mounted, or to a disk partition.
149 Note that this may not work with qcow2 images not generated by e2image.
150 Options -b superblock and -B blocksize can be used same way as for raw
152 images.
153
155 Normally e2image only includes fs metadata, not regular file data. The
156 -a option can be specified to include all data. This will give an
157 image that is suitable to use to clone the entire FS or for backup pur‐
158 poses. Note that this option only works with the raw or QCOW2 formats.
159 The -p switch may be given to show progress. If the file system is
160 being cloned to a flash-based storage device (where reads are very fast
161 and where it is desirable to avoid unnecessary writes to reduce write
162 wear on the device), the -c option which cause e2image to try reading a
163 block from the destination to see if it is identical to the block which
164 e2image is about to copy. If the block is already the same, the write
165 can be skipped. The -n option will cause all of the writes to be no-
166 ops, and print the blocks that would have been written.
167
169 Normally a filesystem starts at the beginning of a partition, and
170 e2image is run on the partition. When working with image files, you
171 don't have the option of using the partition device, so you can specify
172 the offset where the filesystem starts directly with the -o option.
173 Similarly the -O option specifies the offset that should be seeked to
174 in the destination before writing the filesystem.
175 For example, if you have a dd image of a whole hard drive that contains
177 an ext2 fs in a partition starting at 1 MiB, you can clone that fs
178 with:
179 e2image -aro 1048576 img /dev/sda1
181 Or you can clone a fs into an image file, leaving room in the first MiB
183 for a partition table with:
184 e2image -arO 1048576 /dev/sda1 img
186 If you specify at least one offset, and only one file, an in-place move
188 will be performed, allowing you to safely move the filesystem from one
189 offset to another.
190
192 e2image was written by Theodore Ts'o (tytso@mit.edu).
193
195 e2image is part of the e2fsprogs package and is available from
196 http://e2fsprogs.sourceforge.net.
197
199 dumpe2fs(8), debugfs(8)
200E2fsprogs version 1.45.6 March 2020 E2IMAGE(8)