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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 |
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E2IMAGE(8) System Manager's Manual E2IMAGE(8)
e2image - Save critical ext2/ext3/ext4 filesystem metadata to a
file
e2image [ -r|-Q ] [ -f ] [ -b superblock ] [ -B blocksize ]
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.
Option -b superblock can be used to get image from partition with
broken primary superblock. The partition is copied as-is
including broken primary superblock.
Option -B blocksize can be used to set superblock block size.
Normally, e2fsck will search for the superblock at various
different block sizes in an attempt to find the appropriate
blocksize. This search can be fooled in some cases. This option
forces e2fsck to only try locating the superblock at a particular
blocksize. If the superblock is not found, e2fsck will terminate
with a fatal error.
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.
Options -b superblock and -B blocksize can be used same way as
for raw images.
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
2020-12-18. (At that time, the date of the most recent commit
that was found in the repository was 2020-10-01.) 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 1.46-WIP March 2020 E2IMAGE(8)
Pages that refer to this page: e2fsck(8)
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