e2image



E2IMAGE(8)                                                          E2IMAGE(8)




NAME

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


SYNOPSIS

       e2image [ -rsI ] device image-file


DESCRIPTION

       The e2image program will save critical ext2 or ext3 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  catastrophi-
       cally corrupted filesystems.  In the future, e2fsck will be enhanced to
       be able to use the image file to help recover a badly damaged  filesys-
       tem.

       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 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 dam-
       aged.

       To  save  disk  space, 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 --sparse=always
       option to the GNU version of cp.

       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  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
       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

       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
       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 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.



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 1.38             June 2005                        E2IMAGE(8)

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