e2image(8) -- Linux man page

 

NAME

e2image - Save critical ext2/ext3 filesystem data to a file  

SYNOPSIS

e2image [ -r ] device image-file  

DESCRIPTION

The e2image program will save critical filesystem data on the ext2 filesystem 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 be used by an expert in assisting the recovery of 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.

The -r option will create a raw image file instead of a normal image file. A raw image file differs from a normal 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/decompressing 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 data blocks, which the current image file does not have, although this may change in the future.

It is a very good idea to periodically (at boot time and every week or so) to create image files for all of filesystems on a system, as well as saving the partition layout (which can be generated using the using fdisk -l command). Ideally the image file should be stored on some filesystem other that the filesystem whose data it contains, to ensure that its 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 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 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.

 

AUTHOR

e2image was written by Theodore Ts'o (tytso@mit.edu).  

AVAILABILITY

e2image is part of the e2fsprogs package and is available from anonymous http://e2fsprogs.sourceforge.net.  

SEE ALSO

dumpe2fs(8), debugfs(8)