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home | helpx minix x x minixx E2IMAGE(8) System Manager's Manual E2IMAGE(8) NAME e2image - Save critical ext2/ext3/ext4 filesystem metadata to a file SYNOPSIS e2image [ -r|-Q ] [ -f ] [ -b superblock ] [ -B blocksize ] device im- age-file e2image -I device image-file e2image -ra [ -cfnp ] [ -o src_offset ] [ -O dest_offset ] src_fs [ dest_fs ] DESCRIPTION The e2image program will save critical ext2, ext3, or ext4 filesystem 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 filesystems. In the future, e2fsck will be en- hanced 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 require- ment 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 ev- ery 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 dam- aged. 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 ap- ply 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 im- age file taking up 32 megabytes of space on disk will generally com- press down to 3 or 4 megabytes. RESTORING FILESYSTEM METADATA USING AN IMAGE FILE 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 filesys- tem 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 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 under- stand how to create sparse files; the file will become as large as the filesystem itself!) Secondly, the raw image file also includes indi- rect 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 ca- pacity, 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 infor- mation 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 prob- lems related to hash-tree indexed directories. Option -b superblock can be used to get image from partition with bro- ken 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 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 disk space by storing data in special format with pack data closely together, hence avoiding holes while still mini- mizing 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 infor- mation 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 prob- lems 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 Normally e2image only includes fs metadata, not regular file data. The -a option can be specified to include all data. This will give an im- age that is suitable to use to clone the entire FS or for backup pur- poses. 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 be- ing 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 Normally a filesystem starts at the beginning of a partition, and e2im- age 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. Simi- larly 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 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) E2fsprogs version 1.45.5 January 2020 E2IMAGE(8)
NAME | SYNOPSIS | DESCRIPTION | RESTORING FILESYSTEM METADATA USING AN IMAGE FILE | RAW IMAGE FILES | QCOW2 IMAGE FILES | INCLUDING DATA | OFFSETS | AUTHOR | AVAILABILITY | SEE ALSO