NAME¶
virt-diff - Differences between files in two virtual machines
SYNOPSIS¶
virt-diff [--options] -d domain1 -D domain2
virt-diff [--options] -a disk1.img [-a ...] -A disk2.img [-A ...]
DESCRIPTION¶
"virt-diff" lists the differences between files in two virtual
machines or disk images. The usual use case is to show the changes in a VM
after it has been running for a while, by taking a snapshot, running the VM,
and then using this tool to show what changed between the new VM state and the
old snapshot.
This tool will find differences in filenames, file sizes, checksums, extended
attributes, file content and more from a virtual machine or disk image.
However it
does not look at the boot loader, unused space between
partitions or within filesystems, "hidden" sectors and so on. In
other words, it is not a security or forensics tool.
To specify two guests, you have to use the
-a or
-d option(s) for
the first guest, and the
-A or
-D option(s) for the second
guest. The common case is:
virt-diff -a old.img -A new.img
or using names known to libvirt:
virt-diff -d oldguest -D newguest
OPTIONS¶
- --help
- Display brief help.
- -a file
- --add file
- Add file which should be a disk image from the first virtual
machine. If the virtual machine has multiple block devices, you must
supply all of them with separate -a options.
The format of the disk image is auto-detected. To override this and force a
particular format use the --format=.. option.
- -a URI
- --add URI
- Add a remote disk. See "ADDING REMOTE STORAGE" in
guestfish(1).
- --all
- Same as --extra-stats --times --uids
--xattrs.
- --atime
- The default is to ignore changes in file access times, since those are
unlikely to be interesting. Using this flag shows atime differences as
well.
- -A file
- -A URI
- Add a disk image from the second virtual machine.
- --checksum
- --checksum=crc|md5|sha1|sha224|sha256|sha384|sha512
- Use a checksum over file contents to detect when regular files have
changed content.
With no argument, this defaults to using md5. Using an argument, you
can select the checksum type to use. If the flag is omitted then file
times and size are used to determine if a file has changed.
- -c URI
- --connect URI
- If using libvirt, connect to the given URI. If omitted, then we
connect to the default libvirt hypervisor.
If you specify guest block devices directly ( -a), then libvirt is
not used at all.
- --csv
- Write out the results in CSV format (comma-separated values). This format
can be imported easily into databases and spreadsheets, but read
"NOTE ABOUT CSV FORMAT" below.
- --dir-links
- The default is to ignore changed in the number of links in directory
entries, since those are unlikely to be interesting. Using this flag shows
changes to the nlink field of directories.
- --dir-times
- The default is to ignore changed times on directory entries, since those
are unlikely to be interesting. Using this flag shows changes to the time
fields of directories.
- -d guest
- --domain guest
- Add all the disks from the named libvirt guest, as the first guest. Domain
UUIDs can be used instead of names.
- -D guest
- Add all the disks from the named libvirt guest, as the second guest.
Domain UUIDs can be used instead of names.
- --echo-keys
- When prompting for keys and passphrases, virt-diff normally turns echoing
off so you cannot see what you are typing. If you are not worried about
Tempest attacks and there is no one else in the room you can specify this
flag to see what you are typing.
- --extra-stats
- Display extra stats.
- --format=raw|qcow2|..
- --format
- The default for the -a/-A option is to auto-detect the
format of the disk image. Using this forces the disk format for
-a/-A options which follow on the command line. Using
--format with no argument switches back to auto-detection for
subsequent -a/-A options.
For example:
virt-diff --format=raw -a disk.img [...]
forces raw format (no auto-detection) for "disk.img".
virt-diff --format=raw -a disk.img --format -a another.img [...]
forces raw format (no auto-detection) for "disk.img" and reverts
to auto-detection for "another.img".
If you have untrusted raw-format guest disk images, you should use this
option to specify the disk format. This avoids a possible security problem
with malicious guests (CVE-2010-3851).
- -h
- --human-readable
- Display file sizes in human-readable format.
- --keys-from-stdin
- Read key or passphrase parameters from stdin. The default is to try to
read passphrases from the user by opening "/dev/tty".
- --times
- Display time fields.
- --time-days
- Display time fields as days before now (negative if in the future).
Note that 0 in output means "up to 1 day before now", or that the
age of the file is between 0 and 86399 seconds.
- --time-relative
- Display time fields as seconds before now (negative if in the
future).
- --time-t
- Display time fields as seconds since the Unix epoch.
- --uids
- Display UID and GID fields.
- -v
- --verbose
- Enable verbose messages for debugging.
- -V
- --version
- Display version number and exit.
- -x
- Enable tracing of libguestfs API calls.
- --xattrs
- Display extended attributes.
Comma-separated values (CSV) is a deceptive format. It
seems like it
should be easy to parse, but it is definitely not easy to parse.
Myth: Just split fields at commas. Reality: This does
not work reliably.
This example has two columns:
"foo,bar",baz
Myth: Read the file one line at a time. Reality: This does
not work
reliably. This example has one row:
"foo
bar",baz
For shell scripts, use "csvtool" (
http://merjis.com/developers/csv
also packaged in major Linux distributions).
For other languages, use a CSV processing library (eg. "Text::CSV" for
Perl or Python's built-in csv library).
Most spreadsheets and databases can import CSV directly.
EXIT STATUS¶
This program returns 0 if successful, or non-zero if there was an error.
SEE ALSO¶
guestfs(3),
guestfish(1),
virt-cat(1),
virt-copy-out(1),
virt-ls(1),
virt-tar-out(1),
http://libguestfs.org/.
AUTHOR¶
Richard W.M. Jones
http://people.redhat.com/~rjones/
COPYRIGHT¶
Copyright (C) 2009-2014 Red Hat Inc.
LICENSE¶
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 51 Franklin
Street, Fifth Floor, Boston, MA 02110-1301 USA.
BUGS¶
To get a list of bugs against libguestfs, use this link:
https://bugzilla.redhat.com/buglist.cgi?component=libguestfs&product=Virtualization+Tools
To report a new bug against libguestfs, use this link:
https://bugzilla.redhat.com/enter_bug.cgi?component=libguestfs&product=Virtualization+Tools
When reporting a bug, please supply:
- •
- The version of libguestfs.
- •
- Where you got libguestfs (eg. which Linux distro, compiled from source,
etc)
- •
- Describe the bug accurately and give a way to reproduce it.
- •
- Run libguestfs-test-tool(1) and paste the complete, unedited
output into the bug report.
