Merge branch 'maint' into next

[tools/e2fsprogs.git] / misc / e2image.8.in

diff --git a/misc/e2image.8.in b/misc/e2image.8.in
index 45ee272..ef12486 100644 (file)
--- a/misc/e2image.8.in
+++ b/misc/e2image.8.in
@@ -4,57 +4,133 @@
 .\" 
 .TH E2IMAGE 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
 .SH NAME
 .\" 
 .TH E2IMAGE 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
 .SH NAME

-e2image \- Save critical ext2/ext3 filesystem data to a file
+e2image \- Save critical ext2/ext3/ext4 filesystem metadata to a file

 .SH SYNOPSIS
 .B e2image
 [
 .SH SYNOPSIS
 .B e2image
 [

-.B \-rI
+.B \-r|\-Q
+]
+[
+.B \-f
+]
+[
+.B \-b
+.I superblock
+]
+[
+.B \-B
+.I blocksize

 ]
 .I device
 .I image-file
 ]
 .I device
 .I image-file

+.br
+.B e2image
+.B \-I
+.I device
+.I image-file
+.br
+.B e2image
+.B \-ra
+[
+.B \-cfnp
+]
+[
+.B \-o
+.I src_offset
+]
+[
+.B \-O
+.I dest_offset
+]
+.I src_fs
+[
+.I dest_fs
+]

 .SH DESCRIPTION
 The
 .B e2image
 .SH DESCRIPTION
 The
 .B e2image

-program will save critical filesystem data on the ext2 filesystem located on 
-.I device  
-to a file specified by 
+program will save critical ext2, ext3, or ext4 filesystem metadata located on
+.I device
+to a file specified by

 .IR image-file .
 .IR image-file .

-The image file may be examined by 
+The image file may be examined by

 .B dumpe2fs
 and
 .BR  debugfs ,
 by using the
 .B \-i
 .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,
+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
 e2fsck will be enhanced to be able to use the image file to help
 recover a badly damaged filesystem.
 .PP

-If  
+When saving an e2image for debugging purposes, using either the
+.B \-r
+or
+.B \-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 requirement can be
+overridden using the
+.B \-f
+option, but the resulting image file is very likely not going to be useful.
+.PP
+If

 .I image-file
 .I image-file

-is \-, then the output of 
+is \-, then the output of

 .B e2image
 will be sent to standard output, so that the output can be piped to
 .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 
+another program, such as
+.BR gzip (1).
+(Note that this is currently only supported when
+creating a raw image file using the

 .B \-r
 .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
+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
 .BR e2image .)
 .PP
 pipe.  This restriction will hopefully be lifted in a future version of
 .BR e2image .)
 .PP

-The 
-.B \-I 
+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,
+.B 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
+.B \-\-sparse=always
+option to the GNU version of
+.BR cp .
+This does not apply to the QCOW2 image, which is not sparse.
+.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 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
 option will cause e2image to install the metadata stored in the image

-file to the device.    It can be used to restore the filesystem metadata
+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
 back to the device in emergency situations.
 .PP
 .B WARNING!!!!
 The

-.B \-I 
-option should only be used as desperation measure when other
+.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
 alternatives have failed.  If the filesystem has changed since the image
 file was created, data
 .B will


@@ -62,56 +138,178 @@ 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
 backup of the filesystem first, in case you wish to try other recovery
 strategies afterwards.
 .PP

-The 
+.SH RAW IMAGE FILES
+The

 .B \-r
 .B \-r

-option will create a raw image file instead of a normal image file.  
+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,
 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
+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
 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,
+blocks and directory blocks, which the standard image file does not have,

 although this may change in the future.
 .PP
 although this may change in the future.
 .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.
+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
 .PP

-To save disk space, 
+.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
 .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 .  
+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
 .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.
+Option
+.B \-b
+.I superblock
+can be used to get image from partition with broken primary superblock.
+The partition is copied as-is including broken primary superblock.
+.PP
+Option
+.B \-B
+.I 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.
+.PP
+Note that this will work even if you substitute "/dev/hda1" for another raw
+disk image, or QCOW2 image previously created by
+.BR e2image .
+.PP
+.SH QCOW2 IMAGE FILES
+The
+.B \-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 image does, however unlike
+the raw image it is not sparse. The QCOW2 image minimize the amount of disk
+space by storing data in special format with pack data closely together, hence
+avoiding holes while still minimizing size.
+.PP
+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):
+.PP
+.br
+\      \fBe2image \-Q /dev/hda1 hda1.qcow2\fR
+.br
+\      \fBbzip2 -z hda1.qcow2\fR

 .PP
 .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
+Note that QCOW2 image created by
+.B e2image
+is regular QCOW2 image and can be processed by tools aware of QCOW2 format
+such as for example
+.BR qemu-img .
+.PP
+You can convert a qcow2 image into a raw image with:
+.PP
+.br
+\      \fBe2image \-r hda1.qcow2 hda1.raw\fR
+.br
+.PP
+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.
+.PP
+Options
+.B \-b
+.I superblock
+and
+.B \-B
+.I blocksize
+can be used same way as for raw images.
+.PP
+.SH INCLUDING DATA
+Normally
+.B e2image
+only includes fs metadata, not regular file data.  The
+.B \-a
+option can be specified to include all data.  This will
+give an image that is suitable to use to clone the entire FS or
+for backup purposes.  Note that this option only works with the
+raw or QCOW2 formats.  The
+.B \-p
+switch may be given to show progress.  If the file system is being
+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
+.B \-c
+option which cause e2image to try reading a block from the destination
+to see if it is identical to the block which
+.B e2image
+is about to copy.  If the block is already the same, the write can be
+skipped.  The
+.B \-n
+option will cause all of the writes to be no-ops, and print the blocks
+that would have been written.
+.PP
+.SH OFFSETS
+Normally a filesystem starts at the beginning of a partition, and
+.B e2image
+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
+.B \-o
+option.  Similarly the
+.B \-O
+option specifies the offset that should be seeked to in the destination
+before writing the filesystem.
+.PP
+For example, if you have a
+.B 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:
+.PP
+.br
+\      \fBe2image \-aro 1048576 img /dev/sda1\fR
+.br
+.PP
+Or you can clone a fs into an image file, leaving room in the first
+MiB for a partition table with:
+.PP
+.br
+\      \fBe2image -arO 1048576 /dev/sda1 img\fR
+.br
+.PP
+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.

 .SH AUTHOR
 .SH AUTHOR

-.B e2image 
+.B e2image

 was written by Theodore Ts'o (tytso@mit.edu).
 .SH AVAILABILITY
 .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 
+is part of the e2fsprogs package and is available from

 http://e2fsprogs.sourceforge.net.
 .SH SEE ALSO
 .BR dumpe2fs (8),
 http://e2fsprogs.sourceforge.net.
 .SH SEE ALSO
 .BR dumpe2fs (8),