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.
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.