E2IMAGE(8) System Manager's Manual E2IMAGE(8)
NAME
e2image - Save critical ext2/ext3/ext4 file system metadata to a file
SYNOPSIS
e2image [-r|-Q [-af]] [ -b superblock ] [ -B blocksize ] [ -cnps ] [ -o
src_offset ] [ -O dest_offset ] device image-file
e2image -I device image-file
DESCRIPTION
The e2image program will save critical ext2, ext3, or ext4 file system
metadata located on device to a file specified by image-file. The im-
age file may be examined by dumpe2fs and debugfs, by using the -i op-
tion to those programs. This can assist an expert in recovering cata-
strophically corrupted file systems.
It is a very good idea to create image files for all file systems 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 file system other
than the file system whose data it contains, to ensure that this data
is accessible in the case where the file system 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(1). 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
file systems and how many inodes are in use. For a typical 10 Gigabyte
file system, with 200,000 inodes in use out of 1.2 million inodes, the
image file will be approximately 35 Megabytes; a 4 Gigabyte file system
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 im-
age file taking up 32 Megabytes of space on disk will generally com-
press down to 3 or 4 Megabytes.
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.
OPTIONS
-a Include file data in the image file. Normally e2image only in-
cludes fs metadata, not regular file data. This option will
produce 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 (-r) or QCOW2 (-Q) formats. In conjunction with the -r
option it is possible to clone all and only the used blocks of
one file system to another device/image file.
-b superblock
Get image from partition with broken primary superblock by using
the superblock located at file system block number superblock.
The partition is copied as-is including broken primary su-
perblock.
-B blocksize
Set the file system blocksize in bytes. Normally, e2image 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 lo-
cating the superblock with a particular blocksize. If the su-
perblock is not found, e2image will terminate with a fatal er-
ror.
-c Compare each block to be copied from the source device to the
corresponding block in the target image-file. If both are al-
ready the same, the write will be skipped. This is useful 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).
-f Override the read-only requirement for the source file system
when saving the image file using the -r and -Q options. Nor-
mally, if the source file system is in use, the resulting image
file is very likely not going to be useful. In some cases where
the source file system is in constant use this may be better
than no image at all.
-I install the metadata stored in the image file back to the de-
vice. It can be used to restore the file system 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 file system has changed
since the image file was created, data will be lost. In general, you
should make another full image backup of the file system first, in case
you wish to try other recovery strategies afterward.
-n Cause all image writes to be skipped, and instead only print the
block numbers that would have been written.
-o src_offset
Specify offset of the image to be read from the start of the
source device in bytes. See OFFSETS for more details.
-O tgt_offset
Specify offset of the image to be written from the start of the
target image-file in bytes. See OFFSETS for more details.
-p Show progress of image-file creation.
-Q Create a QCOW2-format image file instead of a normal image file,
suitable for use by virtual machine images, and other tools that
can use the .qcow image format. See QCOW2 IMAGE FILES below for
details.
-r Create a raw image file instead of a normal image file. See RAW
IMAGE FILES below for details.
-s Scramble directory entries and zero out unused portions of the
directory blocks in the written image file to avoid revealing
information about the contents of the file system. However,
this will prevent analysis of problems related to hash-tree in-
dexed directories.
RAW IMAGE FILES
The -r option will create a raw image file, which differs from a normal
image file in two ways. First, the file system metadata is placed in
the same relative offset within image-file as it is in the device so
that debugfs(8), dumpe2fs(8), e2fsck(8), losetup(8), etc. and can be
run directly on the raw image file. In order to minimize the amount of
disk space consumed by the raw image file, it 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 file system itself!) Secondly, the raw im-
age file also includes indirect blocks and directory blocks, which the
standard image file does not have.
Raw image files are sometimes used when sending file systems to the
maintainer as part of bug reports to e2fsprogs. When used in this ca-
pacity, the recommended command is as follows (replace hda1 with the
appropriate device for your system):
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 infor-
mation about the contents of the file system that the bug reporter may
wish to keep confidential. To address this concern, the -s option can
be specified to scramble the filenames in the image.
Note that this will work even if you substitute /dev/hda1 for another
raw disk image, or QCOW2 image previously created by e2image.
QCOW2 IMAGE FILES
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 im-
age does, however unlike the raw image it is not sparse. The QCOW2 im-
age minimize the amount of space used by the image by storing it in
special format which packs data closely together, hence avoiding holes
while still minimizing size.
In order to send file system to the maintainer as a part of bug report
to e2fsprogs, use following commands (replace hda1 with the appropriate
device for your system):
e2image -Q /dev/hda1 hda1.qcow2
bzip2 -z hda1.qcow2
This will only send the metadata information, without any data blocks.
As described for RAW IMAGE FILES the -s option can be specified to
scramble the file system names in the image.
Note that the QCOW2 image created by e2image is a 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.
OFFSETS
Normally a file system 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 file system starts directly with the -o option.
Similarly the -O option specifies the offset that should be seeked to
in the destination before writing the file system.
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 image
to a block device with:
e2image -aro 1048576 img /dev/sda1
Or you can clone a file system from a block device 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 file system from one
offset to another.
AUTHOR
e2image was written by Theodore Ts'o (tytso@mit.edu).
AVAILABILITY
e2image is part of the e2fsprogs package and is available from
http://e2fsprogs.sourceforge.net.
SEE ALSO
dumpe2fs(8), debugfs(8) e2fsck(8)
E2fsprogs version 1.47.0 February 2023 E2IMAGE(8)
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