From Linux Man Pages
e2image - Save critical ext2/ext3 filesystem metadata to a file
e2image [ -rsI ] device image-file
DESCRIPTION
The e2image program will save critical ext2 or ext3 filesystem metadata located on device to a file specified by
image-file. The image file may be examined by dumpe2fs and debugfs, by using the -i option to those programs.
This can assist an expert in recovering catastrophically corrupted filesystems. In the future, e2fsck will be
enhanced to be able to use the image file to help recover a badly damaged filesystem.
If image-file is -, then the output of e2image will be sent to standard output, so that the output can be piped
to another program, such as gzip(1). (Note that this is currently only supported when creating a raw image file
using the -r option, since the process of creating a normal image file currently requires random access to the
file, which cannot be done using a pipe. This restriction will hopefully be lifted in a future version of
e2image.)
It is a very good idea to create image files for all of filesystems on a system and save the partition layout
(which can be generated using the fdisk -l command) at regular intervals --- at boot time, and/or every week or
so. The image file should be stored on some filesystem other than the filesystem whose data it contains, to
ensure that this data is accessible in the case where the filesystem has been badly damaged.
To save disk space, e2image creates the image file as a sparse file. Hence, if the image file needs to be copied
to another location, it should either be compressed first or copied using the --sparse=always option to the GNU
version of cp.
The size of an ext2 image file depends primarily on the size of the filesystems and how many inodes are in use.
For a typical 10 gigabyte filesystem, with 200,000 inodes in use out of 1.2 million inodes, the image file will
be approximately 35 megabytes; a 4 gigabyte filesystem with 15,000 inodes in use out of 550,000 inodes will
result in a 3 megabyte image file. Image files tend to be quite compressible; an image file taking up 32
megabytes of space on disk will generally compress down to 3 or 4 megabytes.
RESTORING FILESYSTEM METADATA USING AN IMAGE FILE
The -I option will cause e2image to install the metadata stored in the image file back to the device. It can
be used to restore the filesystem metadata back to the device in emergency situations.
WARNING!!!! The -I option should only be used as a desperation measure when other alternatives have failed. If
the filesystem has changed since the image file was created, data will be lost. In general, you should make a
full image backup of the filesystem first, in case you wish to try other recovery strategies afterwards.
RAW IMAGE FILES
The -r option will create a raw image file instead of a normal image file. A raw image file differs from a nor-
mal image file in two ways. First, the filesystem metadata is placed in the proper position so that e2fsck,
dumpe2fs, debugfs, etc. can be run directly on the raw image file. In order to minimize the amount of disk space
consumed by a raw image file, the file is created as a sparse file. (Beware of copying or compressing/decom-
pressing this file with utilities that don't understand how to create sparse files; the file will become as large
as the filesystem itself!) Secondly, the raw image file also includes indirect blocks and directory blocks,
which the standard image file does not have, although this may change in the future.
Raw image files are sometimes used when sending filesystems to the maintainer as part of bug reports to
e2fsprogs. When used in this capacity, the recommended command is as follows (replace hda1 with the appropriate
device):
e2image -r /dev/hda1 - | bzip2 > hda1.e2i.bz2
This will only send the metadata information, without any data blocks. However, the filenames in the directory
blocks can still reveal information about the contents of the filesystem that the bug reporter may wish to keep
confidential. To address this concern, the -s option can be specified. This will cause e2image to scramble
directory entries and zero out any unused portions of the directory blocks before writing the image file.
However, the -s option will prevent analysis of problems related to hash-tree indexed directories.
AVAILABILITY
e2image is part of the e2fsprogs package and is available from http://e2fsprogs.sourceforge.net.
RELATED
dumpe2fs(8), debugfs(8)
CATEGORY