e2image(8) — Linux manual page

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)

NAME         top

       e2image - Save critical ext2/ext3/ext4 filesystem metadata to a
       file

SYNOPSIS         top

       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 ]

DESCRIPTION         top

       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.

RESTORING FILESYSTEM METADATA USING AN IMAGE FILE         top

       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.

RAW IMAGE FILES         top

       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.

QCOW2 IMAGE FILES         top

       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.

INCLUDING DATA         top

       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.

OFFSETS         top

       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.

AUTHOR         top

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

AVAILABILITY         top

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

SEE ALSO         top

       dumpe2fs(8), debugfs(8)

COLOPHON         top

       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
       2021-04-01.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-02-28.)  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 1.46.2      February 2021                   E2IMAGE(8)

Pages that refer to this page: e2fsck(8)