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92dcfb7692
This commit adds support for converting QCOW2 image created previously with e2image into raw image. The QCOW2 image is detected automatically, so there is not new option. Just use following command: e2image -r image.qcow image.raw No that this tool is aimed to quickly convert qcow2 image created with e2image into raw image. In order to improve speed we are doing some assumption I believe might not be true for regular qcow2 images. So it was not tested with regular QCOW2 images and it might not work with them. The intention of this tool is only convert images previously created by e2image. Note that there is nothing special with QCOW2 images created by e2images and it can be used with tools like qemu-img, or qemu-nbd without any problems. Signed-off-by: Lukas Czerner <lczerner@redhat.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
185 lines
6.5 KiB
Groff
185 lines
6.5 KiB
Groff
.\" -*- nroff -*-
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.\" Copyright 2001 by Theodore Ts'o. All Rights Reserved.
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.\" This file may be copied under the terms of the GNU Public License.
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.\"
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.TH E2IMAGE 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
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.SH NAME
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e2image \- Save critical ext2/ext3/ext4 filesystem metadata to a file
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.SH SYNOPSIS
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.B e2image
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[
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.B \-rsI
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]
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.I device
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.I image-file
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.SH DESCRIPTION
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The
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.B e2image
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program will save critical ext2, ext3, or ext4 filesystem metadata located on
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.I device
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to a file specified by
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.IR image-file .
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The image file may be examined by
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.B dumpe2fs
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and
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.BR debugfs ,
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by using the
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.B \-i
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option to those programs. This can assist an expert in
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recovering catastrophically corrupted filesystems. In the future,
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e2fsck will be enhanced to be able to use the image file to help
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recover a badly damaged filesystem.
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.PP
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If
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.I image-file
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is \-, then the output of
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.B e2image
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will be sent to standard output, so that the output can be piped to
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another program, such as
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.BR gzip (1).
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(Note that this is currently only supported when
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creating a raw image file using the
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.B \-r
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option, since the process of creating a normal image file, or QCOW2
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image currently
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requires random access to the file, which cannot be done using a
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pipe. This restriction will hopefully be lifted in a future version of
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.BR e2image .)
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.PP
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It is a very good idea to create image files for all of
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filesystems on a system and save the partition
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layout (which can be generated using the
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.B fdisk \-l
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command) at regular intervals --- at boot time, and/or every week or so.
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The image file should be stored on some filesystem other than
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the filesystem whose data it contains, to ensure that this data is
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accessible in the case where the filesystem has been badly damaged.
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.PP
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To save disk space,
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.B e2image
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creates the image file as a sparse file, or in QCOW2 format.
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Hence, if the sparse image file
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needs to be copied to another location, it should
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either be compressed first or copied using the
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.B \-\-sparse=always
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option to the GNU version of
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.BR cp .
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This does not apply to the QCOW2 image, which is not sparse.
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.PP
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The size of an ext2 image file depends primarily on the size of the
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filesystems and how many inodes are in use. For a typical 10 gigabyte
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filesystem, with 200,000 inodes in use out of 1.2 million inodes, the
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image file will be approximately 35 megabytes; a 4 gigabyte filesystem with
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15,000 inodes in use out of 550,000 inodes will result in a 3 megabyte
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image file. Image files tend to be quite
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compressible; an image file taking up 32 megabytes of space on
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disk will generally compress down to 3 or 4 megabytes.
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.PP
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.SH RESTORING FILESYSTEM METADATA USING AN IMAGE FILE
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.PP
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The
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.B \-I
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option will cause e2image to install the metadata stored in the image
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file back to the device. It can be used to restore the filesystem metadata
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back to the device in emergency situations.
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.PP
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.B WARNING!!!!
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The
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.B \-I
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option should only be used as a desperation measure when other
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alternatives have failed. If the filesystem has changed since the image
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file was created, data
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.B will
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be lost. In general, you should make a full image
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backup of the filesystem first, in case you wish to try other recovery
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strategies afterwards.
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.PP
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.SH RAW IMAGE FILES
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The
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.B \-r
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option will create a raw image file instead of a normal image file.
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A raw image file differs
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from a normal image file in two ways. First, the filesystem metadata is
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placed in the proper position so that e2fsck, dumpe2fs, debugfs,
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etc. can be run directly on the raw image file. In order to minimize
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the amount of disk space consumed by a raw image file, the file is
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created as a sparse file. (Beware of copying or
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compressing/decompressing this file with utilities that don't understand
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how to create sparse files; the file will become as large as the
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filesystem itself!) Secondly, the raw image file also includes indirect
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blocks and directory blocks, which the standard image file does not have,
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although this may change in the future.
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.PP
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Raw image files are sometimes used when sending filesystems to the maintainer
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as part of bug reports to e2fsprogs. When used in this capacity, the
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recommended command is as follows (replace hda1 with the appropriate device):
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.PP
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.br
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\ \fBe2image \-r /dev/hda1 \- | bzip2 > hda1.e2i.bz2\fR
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.PP
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This will only send the metadata information, without any data blocks.
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However, the filenames in the directory blocks can still reveal
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information about the contents of the filesystem that the bug reporter
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may wish to keep confidential. To address this concern, the
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.B \-s
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option can be specified. This will cause
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.B e2image
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to scramble directory entries and zero out any unused portions
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of the directory blocks before writing the image file. However,
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the
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.B \-s
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option will prevent analysis of problems related to hash-tree indexed
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directories.
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.PP
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Note that this will work even if you substitute "/dev/hda1" for another raw
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disk image, or QCOW2 image previously created by
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.BR e2image .
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.PP
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.SH QCOW2 IMAGE FILES
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The
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.B \-Q
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option will create a QCOW2 image file instead of a normal, or raw image file.
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A QCOW2 image contains all the information the raw image does, however unlike
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the raw image it is not sparse. The QCOW2 image minimize the amount of disk
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space by storing data in special format with pack data closely together, hence
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avoiding holes while still minimizing size.
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.PP
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In order to send filesystem to the maintainer as a part of bug report to
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e2fsprogs, use following commands (replace hda1 with the appropriate device):
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.PP
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.br
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\ \fBe2image \-Q /dev/hda1 hda1.qcow2\fR
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.br
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\ \fBbzip2 -z hda1.qcow2\fR
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.PP
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This will only send the metadata information, without any data blocks.
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However, the filenames in the directory blocks can still reveal
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information about the contents of the filesystem that the bug reporter
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may wish to keep confidential. To address this concern, the
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.B \-s
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option can be specified. This will cause
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.B e2image
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to scramble directory entries and zero out any unused portions
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of the directory blocks before writing the image file. However, the
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.B \-s
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option will prevent analysis of problems related to hash-tree indexed
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directories.
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.PP
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Note that QCOW2 image created by
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.B e2image
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is regular QCOW2 image and can be processed by tools aware of QCOW2 format
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such as for example
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.BR qemu-img .
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.PP
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.SH AUTHOR
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.B e2image
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was written by Theodore Ts'o (tytso@mit.edu).
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.SH AVAILABILITY
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.B e2image
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is part of the e2fsprogs package and is available from
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http://e2fsprogs.sourceforge.net.
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.SH SEE ALSO
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.BR dumpe2fs (8),
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.BR debugfs (8)
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