mirror of
https://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git
synced 2024-11-24 18:43:53 +08:00
140 lines
4.8 KiB
Groff
140 lines
4.8 KiB
Groff
.\" -*- nroff -*-
|
|
.\" Copyright 2001 by Theodore Ts'o. All Rights Reserved.
|
|
.\" This file may be copied under the terms of the GNU Public License.
|
|
.\"
|
|
.TH E2IMAGE 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
|
|
.SH NAME
|
|
e2image \- Save critical ext2/ext3 filesystem data to a file
|
|
.SH SYNOPSIS
|
|
.B e2image
|
|
[
|
|
.B \-rsI
|
|
]
|
|
.I device
|
|
.I image-file
|
|
.SH DESCRIPTION
|
|
The
|
|
.B e2image
|
|
program will save critical filesystem data on the ext2 filesystem located on
|
|
.I device
|
|
to a file specified by
|
|
.IR image-file .
|
|
The image file may be examined by
|
|
.B dumpe2fs
|
|
and
|
|
.BR debugfs ,
|
|
by using the
|
|
.B \-i
|
|
option to those programs. This can be used by an expert in assisting
|
|
the recovery of 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.
|
|
.PP
|
|
If
|
|
.I image-file
|
|
is \-, then the output of
|
|
.B e2image
|
|
will be sent to standard output, so that the output can be piped to
|
|
another program, such as
|
|
.BR gzip (1).
|
|
(Note that is currently only supported when
|
|
creating a raw image file using the
|
|
.B \-r
|
|
option, since the process of creating a normal image file currently
|
|
requires random-access access to the file, which can not be done using a
|
|
pipe. This restriction will hopefully be lifted in a future version of
|
|
.BR e2image .)
|
|
.PP
|
|
It is a very good idea to periodically (at boot time and
|
|
every week or so) to create image files for all of
|
|
filesystems on a system, as well as saving the partition
|
|
layout (which can be generated using the using
|
|
.B fdisk \-l
|
|
command). Ideally the image file should be stored on some filesystem
|
|
other that
|
|
the filesystem whose data it contains, to ensure that its data is
|
|
accessible in the case where the filesystem has been badly damaged.
|
|
.PP
|
|
To save disk space,
|
|
.B e2image
|
|
creates the image file as a sparse file.
|
|
Hence, if the image file
|
|
needs to be copied to another location, it should
|
|
either be compressed first or copied using the
|
|
.B \-\-sparse=always
|
|
option to GNU version of
|
|
.BR cp .
|
|
.PP
|
|
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 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.
|
|
.PP
|
|
.SH RESTORING FILESYSTEM METADATA USING AN IMAGE FILE
|
|
.PP
|
|
The
|
|
.B \-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.
|
|
.PP
|
|
.B WARNING!!!!
|
|
The
|
|
.B \-I
|
|
option should only be used as desperation measure when other
|
|
alternatives have failed. If the filesystem has changed since the image
|
|
file was created, data
|
|
.B 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.
|
|
.PP
|
|
.SH RAW IMAGE FILES
|
|
The
|
|
.B \-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.
|
|
.PP
|
|
Raw image files are sometimes used when sending filesystems to as part
|
|
of bug reports to e2fsprogs. When used in this capacity, the
|
|
recommended command is (replace hda1 with appropriate device):
|
|
.PP
|
|
.br
|
|
\ \fBe2image -r /dev/hda1 - | bzip2 > hda1.e2i.bz2\fR
|
|
.PP
|
|
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
|
|
.B \-s
|
|
option can be specified. This will cause
|
|
.B e2image
|
|
to scramble directory entries and zero out any unused portions
|
|
of the directory blocks before writing them to the image file.
|
|
.PP
|
|
.SH AUTHOR
|
|
.B e2image
|
|
was written by Theodore Ts'o (tytso@mit.edu).
|
|
.SH AVAILABILITY
|
|
.B e2image
|
|
is part of the e2fsprogs package and is available from
|
|
http://e2fsprogs.sourceforge.net.
|
|
.SH SEE ALSO
|
|
.BR dumpe2fs (8),
|
|
.BR debugfs (8)
|
|
|