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NAME | SYNOPSIS | DESCRIPTION | RESTORING FILESYSTEM METADATA USING AN IMAGE FILE | RAW IMAGE FILES | QCOW2 IMAGE FILES | INCLUDING DATA | OFFSETS | AUTHOR | AVAILABILITY | SEE ALSO | COLOPHON |
E2IMAGE(8) System Manager's Manual E2IMAGE(8)
e2image - Save critical ext2/ext3/ext4 filesystem metadata to a file
e2image [ -r|Q ] [ -fr ] device image-file
e2image -I device image-file
e2image -ra [ -cfnp ] [ -o src_offset ] [ -O dest_offset ] src_fs [
dest_fs ]
The e2image program will save critical ext2, ext3, or ext4 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.
When saving an e2image for debugging purposes, using either the -r or
-Q options, the filesystem must be unmounted or be mounted read/only,
in order for the image file to be in a consistent state. This
requirement can be overridden using the -f option, but the resulting
image file is very likely not going to be useful.
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, or QCOW2 image 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,
or in QCOW2 format. Hence, if the sparse 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.
This does not apply to the QCOW2 image, which is not sparse.
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.
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.
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 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.
Note that this will work even if you substitute "/dev/hda1" for
another raw disk image, or QCOW2 image previously created by e2image.
The -Q option will create a QCOW2 image file instead of a normal, or
raw image file. A QCOW2 image contains all the information the raw
image does, however unlike the raw image it is not sparse. The QCOW2
image minimize the amount of disk space by storing data in special
format with pack data closely together, hence avoiding holes while
still minimizing size.
In order to send filesystem to the maintainer as a part of bug report
to e2fsprogs, use following commands (replace hda1 with the
appropriate device):
e2image -Q /dev/hda1 hda1.qcow2
bzip2 -z hda1.qcow2
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.
Note that QCOW2 image created by e2image is regular QCOW2 image and
can be processed by tools aware of QCOW2 format such as for example
qemu-img.
You can convert a qcow2 image into a raw image with:
e2image -r hda1.qcow2 hda1.raw
This can be useful to write a qcow2 image containing all data to a
sparse image file where it can be loop mounted, or to a disk
partition. Note that this may not work with qcow2 images not
generated by e2image.
Normally e2image only includes fs metadata, not regular file data.
The -a option can be specified to include all data. This will give
an image that is suitable to use to clone the entire FS or for backup
purposes. Note that this option only works with the raw or QCOW2
formats. The -p switch may be given to show progress. If the file
system is being cloned to a flash-based storage device (where reads
are very fast and where it is desirable to avoid unnecessary writes
to reduce write wear on the device), the -c option which cause
e2image to try reading a block from the destination to see if it is
identical to the block which e2image is about to copy. If the block
is already the same, the write can be skipped. The -n option will
cause all of the writes to be no-ops, and print the blocks that would
have been written.
Normally a filesystem starts at the beginning of a partition, and
e2image is run on the partition. When working with image files, you
don't have the option of using the partition device, so you can
specify the offset where the filesystem starts directly with the -o
option. Similarly the -O option specifies the offset that should be
seeked to in the destination before writing the filesystem.
For example, if you have a dd image of a whole hard drive that
contains an ext2 fs in a partition starting at 1 MiB, you can clone
that fs with:
e2image -aro 1048576 img /dev/sda1
Or you can clone a fs into an image file, leaving room in the first
MiB for a partition table with:
e2image -arO 1048576 /dev/sda1 img
If you specify at least one offset, and only one file, an in-place
move will be performed, allowing you to safely move the filesystem
from one offset to another.
e2image was written by Theodore Ts'o (tytso@mit.edu).
e2image is part of the e2fsprogs package and is available from
http://e2fsprogs.sourceforge.net.
dumpe2fs(8), debugfs(8)
This page is part of the e2fsprogs (utilities for ext2/3/4
filesystems) project. Information about the project can be found at
⟨http://e2fsprogs.sourceforge.net/⟩. It is not known how to report
bugs for this man page; if you know, please send a mail to
man-pages@man7.org. This page was obtained from the project's
upstream Git repository
⟨git://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git⟩ on 2017-07-05.
If you discover any rendering problems in this HTML version of the
page, or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the information
in this COLOPHON (which is not part of the original manual page),
send a mail to man-pages@man7.org
E2fsprogs version 1.43.5-WIP February 2017 E2IMAGE(8)
Pages that refer to this page: e2fsck(8)