X-Git-Url: https://git.whamcloud.com/?a=blobdiff_plain;f=misc%2Fe2image.8.in;h=a0300b447cc5ec8312f8b832620852e70e783cb5;hb=25a9fe2894a147f5d0d2320357f78c7ff9de09e3;hp=411a7fd6def6fea57a87d22cd41704772a0417ce;hpb=6304baf255b0d3b2fc57619acd16a4107e83bd02;p=tools%2Fe2fsprogs.git diff --git a/misc/e2image.8.in b/misc/e2image.8.in index 411a7fd..a0300b4 100644 --- a/misc/e2image.8.in +++ b/misc/e2image.8.in @@ -4,19 +4,18 @@ .\" .TH E2IMAGE 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@" .SH NAME -e2image \- Save critical ext2 filesystem data to a file +e2image \- Save critical ext2/ext3 filesystem metadata to a file .SH SYNOPSIS .B e2image [ -.B \-r +.B \-rsI ] .I device .I image-file .SH DESCRIPTION The .B e2image -program will save critical filesystem data on the ext2 filesystem located on -display or change the filesystem label on the ext2 filesystem located on +program will save critical ext2 or ext3 filesystem metadata located on .I device to a file specified by .IR image-file . @@ -26,33 +25,33 @@ 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, +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. .PP -The +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 this is currently only supported when +creating a raw image file using the .B \-r -option will create a raw image file instead. 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 data blocks, which the current image file does not have --- -although this may change in the future. +option, since the process of creating a normal image file 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 +.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 +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 +.B 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. .PP To save disk space, @@ -61,25 +60,81 @@ 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 +.B \-\-sparse=always +option to the 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 +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. .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 a 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 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): +.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 the image file. However, +the +.B \-s +option will prevent analysis of problems related to hash-tree indexed +directories. +.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 anonymous +is part of the e2fsprogs package and is available from http://e2fsprogs.sourceforge.net. .SH SEE ALSO .BR dumpe2fs (8),