guestfs-recipes(1) Virtualization Support guestfs-recipes(1)NAMEguestfs-recipes - libguestfs, guestfish and virt tools recipes
DESCRIPTION
This page contains recipes for and links to things you can do using
libguestfs, guestfish(1) and the virt tools.
Audit a virtual machine for setuid files
See: "EXAMPLES" in virt-ls(1).
Change the background image in a Windows XP VM
The links below explain how to use guestfish(1) to change the
background image for a user of a Windows XP VM. Unfortunately the
technique appears to be substantially different for each version of
Windows.
https://lists.fedoraproject.org/pipermail/virt/2011-May/002655.html
https://lists.fedoraproject.org/pipermail/virt/2011-May/002658.html
Checksum a file or device within a disk image
To checksum a whole device, or a partition, LV etc within a disk image:
guestfish --ro -a disk.img run : checksum-device md5 /dev/sda1
Replace "md5" with the type of checksum you want. See
"guestfs_checksum_device" in guestfs(3) for a list of supported types.
"/dev/sda1" means "the first partition". You could use "/dev/sda" to
checksum the whole disk image, or the name of a logical volume or RAID
device.
To checksum a single file:
guestfish --ro -a disk.img -i checksum sha256 /etc/passwd
or for a Windows guest:
guestfish --ro -a disk.img -i \
checksum sha256 'win:\windows\system32\config\SOFTWARE'
Cloning a virtual machine
Use a combination of tools like cp(1), dd(1), and virt tools like
virt-sysprep(1), virt-sparsify(1) and virt-resize(1).
For more details, see: "COPYING AND CLONING" in virt-sysprep(1).
Convert a CD-ROM / DVD / ISO to a tarball
This converts input "cd.iso" to output "cd.tar.gz":
guestfish --ro -a cd.iso -m /dev/sda tgz-out / cd.tar.gz
To export just a subdirectory, eg. "/files", do:
guestfish --ro -a cd.iso -m /dev/sda tgz-out /files cd.tar.gz
Convert from one format/filesystem to another
If you have a data disk in one format / filesystem / partition / volume
manager, you can convert it another using this technique.
In this example, we start with a data disk that has a single partition
containing a filesystem, and we want to create another disk that
contains the same files but on an ext3 filesystem embedded in a logical
volume on a sparse raw-format disk.
First create the formatted-but-empty target disk:
truncate -s 10G target.img
virt-format -a target.img --partition=mbr --lvm --filesystem=ext3
Now, pipe two guestfish instances together to transfer the old data to
the new disk:
guestfish --ro -a source.img -m /dev/sda1 -- tar-out / - | \
guestfish --rw -a target.img -m /dev/VG/LV -- tar-in - /
To browse the final disk image, do:
guestfish --ro -a target.img -m /dev/VG/LV
><fs> ll /
This technique is quite powerful, allowing you for example to split up
source directories over the target filesystems.
Note this won't work (at least, not directly) for bootable virtual
machine disks because it doesn't copy over the boot loader.
Create empty disk images
The virt-format(1) tool can do this directly.
Use virt-make-fs(1) to create a disk image with content. This can also
create some standard disk images such as virtual floppy devices (VFDs).
You can also use the guestfish(1)-N option to create empty disk
images. The useful guide below explains the options available.
https://rwmj.wordpress.com/2010/09/08/new-guestfish-n-options-in-1-5-9/#content
Delete a file (or other simple file operations)
Use guestfish. To delete a file:
guestfish -a disk.img -i rm /file/to/delete
To touch a file (bring it up to date or create it):
guestfish -a disk.img -i touch /file/to/touch
To stat a file. Since this is a read-only operation, we can make it
safer by adding the --ro flag.
guestfish --ro -a disk.img -i stat /file/to/stat
There are dozens of these commands. See guestfish(1) or the output of
"guestfish -h"
Diff two guests; compare a snapshot to the current version
virt-ls(1) provides a simple way to find the differences between two
guests (for example if they were originally cloned from the same
source), or between two snapshots from the same guest. See
"DIFFERENCES IN SNAPSHOTS AND BACKING FILES" in virt-ls(1).
There are also experimental patches on the mailing list for a "virt-
diff" tool.
Dump raw filesystem content from inside a disk image or VM
You can use the guestfish(1) "download" command to extract the raw
filesystem content from any filesystem in a disk image or a VM (even
one which is encrypted or buried inside an LV or RAID device):
guestfish --ro -a disk.img run : download /dev/sda1 sda1.img
guestfish --ro -d Guest run : download /dev/vg_guest/lv_root lv.img
To download to stdout, replace the filename with a "-" character:
guestfish --ro -a disk.img run : download /dev/sda1 - | gzip > sda1.gz
To list the filesystems in a disk image, use virt-filesystems(1).
See also "Uploading raw filesystem content".
Edit grub configuration in a VM
You can use this to:
· Fix a virtual machine that does not boot.
· Change which kernel is used to boot the VM.
· Change kernel command line options.
Use virt-edit(1) to edit the grub configuration:
virt-edit -d BrokenGuest /boot/grub2/grub.cfg
or for general tinkering inside an unbootable VM use virt-rescue(1)
like this:
virt-rescue -d BrokenGuest
Export any directory from a VM
To export "/home" from a VM into a local directory use
virt-copy-out(1):
virt-copy-out -d Guest /home .
Notes:
· The final dot of the command is not a printing error. It means we
want to copy out to the current directory.
· This creates a directory called "home" under the current directory.
If the guest is a Windows guest then you can use drive letters and
backslashes, but you must prefix the path with "win:" and quote it to
protect it from the shell, like this:
virt-copy-out -d WinGuest 'win:c:\windows\system32\config' .
To get the output as a compressed tarball, do:
virt-tar-out -d Guest /home - | gzip --best > home.tar.gz
Although it sounds tempting, this is usually not a reliable way to get
a backup from a running guest. See the entry in the FAQ:
http://libguestfs.org/FAQ.html#backup
Find out which user is using the most space
This simple script examines a Linux guest to find out which user is
using the most space in their home directory:
#!/bin/sh -
set -e
vm="$1"
dir=/home
eval $(guestfish --ro -d "$vm" -i --listen)
for d in $(guestfish --remote ls "$dir"); do
echo -n "$dir/$d"
echo -ne '\t'
guestfish --remote du "$dir/$d";
done | sort -nr -k 2
guestfish --remote exit
Get DHCP address from a VM
The link below explains the many different possible techniques for
getting the last assigned DHCP address of a virtual machine.
https://rwmj.wordpress.com/2011/03/31/tip-code-for-getting-dhcp-address-from-a-virtual-machine-disk-image/#content
In the libguestfs source examples directory you will find the latest
version of the "virt-dhcp-address.c" program.
Get the operating system product name string
Save the following script into a file called "product-name.sh":
#!/bin/sh -
set -e
eval "$(guestfish --ro -d "$1" --i --listen)"
root="$(guestfish --remote inspect-get-roots)"
guestfish --remote inspect-get-product-name "$root"
guestfish --remote exit
Make the script executable and run it on a named guest:
# product-name.sh RHEL60x64
Red Hat Enterprise Linux Server release 6.0 (Santiago)
You can also use an XPath query on the virt-inspector(1) XML using the
"xpath" command line tool or from your favourite programming language:
# virt-inspector RHEL60x64 > xml
# xpath '//product_name' < xml
Found 1 nodes:
-- NODE --
<product_name>Red Hat Enterprise Linux Server release 6.0 (Santiago)</product_name>
Get the default boot kernel for a Linux VM
The link below contains a program to print the default boot kernel for
a Linux VM.
https://rwmj.wordpress.com/2010/10/30/tip-use-augeas-to-get-the-default-boot-kernel-for-a-vm/#content
It uses Augeas, and the technique is generally applicable for many
different tasks, such as:
· listing the user accounts in the guest
· what repositories is it configured to use
· what NTP servers does it connect to
· what were the boot messages last time it booted
· listing who was logged in recently
http://augeas.net/
Hanging guests
There are various ways to use libguestfs to find out why a guest is
hanging or unresponsive:
1. Read the log files using virt-cat:
virt-cat Guest /var/log/messages | less
2. Read the Windows Event Log (Windows Vista or later only):
https://rwmj.wordpress.com/2011/04/17/decoding-the-windows-event-log-using-guestfish/#content
3. Find out which files were last updated in a guest:
https://rwmj.wordpress.com/2012/02/27/using-libguestfs-to-find-out-why-a-windows-guest-was-hanging/#content
This might give you a clue as to what program is running.
Hex-dumping sectors from the guest
Hex-dump the boot partition:
guestfish --ro -a disk.img run : pread-device /dev/sda 0x200 0 |
hexdump -C
Hex-editing sectors in the guest
Hex-edit the first sector (boot partition):
guestfish --rw -a disk.img run : hexedit /dev/sda 0x200
Install RPMs in a guest
The link below contains a method to install RPMs in a guest. In fact
the RPMs are just uploaded to the guest along with a "firstboot" script
that installs them next time the guest is booted. You could use this
technique to install vital security updates in an offline guest.
https://rwmj.wordpress.com/2010/12/01/tip-install-rpms-in-a-guest/#content
Since libguestfs 1.20, virt-sysprep(1) has an option for installing
firstboot scripts in Linux guests.
List applications installed in a VM
Save the following to a file "list-apps.sh":
#!/bin/sh -
set -e
eval "$(guestfish --ro -d "$1" --i --listen)"
root="$(guestfish --remote inspect-get-roots)"
guestfish --remote inspect-list-applications "$root"
guestfish --remote exit
Make the file executable and then you can run it on any named virtual
machine:
# list-apps.sh WinGuest
[0] = {
app_name: Mozilla Firefox (3.6.12)
app_display_name: Mozilla Firefox (3.6.12)
app_epoch: 0
app_version: 3.6.12 (en-GB)
app_release:
app_install_path: C:\Program Files\Mozilla Firefox
app_trans_path:
app_publisher: Mozilla
app_url: http://www.mozilla.com/en-GB/
app_source_package:
app_summary:
app_description: Mozilla Firefox
}
[1] = {
app_name: VLC media player
app_display_name: VLC media player 1.1.5
app_epoch: 0
app_version: 1.1.5
app_release:
app_install_path: C:\Program Files\VideoLAN\VLC
app_trans_path:
app_publisher: VideoLAN
app_url: http://www.videolan.org/
app_source_package:
app_summary:
app_description:
}
If you want to run the script on disk images (instead of libvirt
virtual machines), change "-d "$1"" to "-a "$1"". See also
virt-inspector(1).
List files and directories in a VM
Use virt-ls(1).
List services in a Windows VM
The link below contains a script that can be used to list out the
services from a Windows VM, and whether those services run at boot time
or are loaded on demand.
https://rwmj.wordpress.com/2010/12/10/tip-list-services-in-a-windows-guest/#content
Make a disk image sparse
Use virt-sparsify(1).
Monitor disk usage over time
You can use virt-df(1) to monitor disk usage of your guests over time.
The link below contains a guide.
http://virt-tools.org/learning/advanced-virt-df/
Reading the Windows Event Log from Windows Vista (or later)guestfish(1) plus the tools described in the link below can be used to
read out the Windows Event Log from any virtual machine running Windows
Vista or a later version.
https://rwmj.wordpress.com/2011/04/17/decoding-the-windows-event-log-using-guestfish/#content
Remove root password (Linux)
Using the virt-edit(1)-e option you can do simple replacements on
files. One use is to remove the root password from a Linux guest:
virt-edit domname /etc/passwd -e 's/^root:.*?:/root::/'
Remove Administrator password (Windows)
The link below contains one technique for removing the Administrator
password from a Windows VM, or to be more precise, it gives you a
command prompt the next time you log in which you can use to bypass any
security:
https://mdbooth.wordpress.com/2010/10/18/resetting-a-windows-guests-administrator-password-with-guestfish/
Sysprepping a virtual machine (Windows)
It is possible to do a "sysprep" using libguestfs alone, although not
straightforward. Currently there is code in the Aeolus Oz project
which does this (using libguestfs). It is likely we will add this to
virt-sysprep(1) in future.
https://github.com/clalancette/oz
https://www.redhat.com/archives/virt-tools-list/2011-May/msg00019.html
Unpack a live CD
Linux live CDs often contain multiple layers of disk images wrapped
like a Russian doll. You can use guestfish(1) to look inside these
multiple layers, as outlined in the guide below.
https://rwmj.wordpress.com/2009/07/15/unpack-the-russian-doll-of-a-f11-live-cd/#content
Uploading and downloading files
The link below contains general tips on uploading (copying in) and
downloading (copying out) files from VMs.
https://rwmj.wordpress.com/2010/12/02/tip-uploading-and-downloading/#content
Uploading raw filesystem content
You can use guestfish(1) to upload whole filesystems into a VM, even
into a filesystem which is encrypted or buried inside an LV or RAID
device:
guestfish --rw -a disk.img run : upload sda1.img /dev/sda1
guestfish --rw -d Guest run : upload lv.img /dev/vg_guest/lv_root
One common problem is that the filesystem isn't the right size for the
target. If it is too large, there's not much you can do with
libguestfs - you have to prepare the filesystem differently. But if
the filesystem needs to expand into the target, you can use guestfish
to resize it to the right size:
guestfish --rw -d Guest run : \
upload lv.img /dev/vg_guest/lv_root : \
resize2fs /dev/vg_guest/lv_root
(or use "ntfsresize" if the filesystem is NTFS).
Use libguestfs tools on VMware ESX guests
The link below explains how to use libguestfs, guestfish(1) and the
virt tools on any VMware ESX guests, by first sharing the VMware VMFS
over sshfs.
https://rwmj.wordpress.com/2011/05/10/tip-use-libguestfs-on-vmware-esx-guests/#content
SEE ALSOguestfs(3), guestfish(1), guestfs-examples(3), guestfs-erlang(3),
guestfs-java(3), guestfs-lua(3), guestfs-ocaml(3), guestfs-perl(3),
guestfs-python(3), guestfs-ruby(3), http://libguestfs.org/.
AUTHORS
Richard W.M. Jones ("rjones at redhat dot com")
COPYRIGHT
Copyright (C) 2009-2013 Red Hat Inc.
LICENSE
This manual page contains examples which we hope you will use in your
programs. The examples may be freely copied, modified and distributed
for any purpose without any restrictions.
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.
libguestfs-1.20.11 2013-08-27 guestfs-recipes(1)