virt-sysprep(1) Virtualization Support virt-sysprep(1)NAMEvirt-sysprep - Reset, unconfigure or customize a virtual machine so
clones can be made
SYNOPSISvirt-sysprep [--options] -d domname
virt-sysprep [--options] -a disk.img [-a disk.img ...]
DESCRIPTION
Virt-sysprep can reset or unconfigure a virtual machine so that clones
can be made from it. Steps in this process include removing SSH host
keys, removing persistent network MAC configuration, and removing user
accounts. Virt-sysprep can also customize a virtual machine, for
instance by adding SSH keys, users or logos. Each step can be enabled
or disabled as required.
Virt-sysprep modifies the guest or disk image in place. The guest must
be shut down. If you want to preserve the existing contents of the
guest, you must snapshot, copy or clone the disk first. See "COPYING
AND CLONING" below.
You do not need to run virt-sysprep as root. In fact we'd generally
recommend that you don't. The time you might want to run it as root is
when you need root in order to access the disk image, but even in this
case it would be better to change the permissions on the disk image to
be writable as the non-root user running virt-sysprep.
"Sysprep" stands for "system preparation" tool. The name comes from
the Microsoft program "sysprep.exe" which is used to unconfigure
Windows machines in preparation for cloning them. Having said that,
virt-sysprep does not currently work on Microsoft Windows guests. We
plan to support Windows sysprepping in a future version, and we already
have code to do it.
OPTIONS--help
Display brief help.
-a file
--add file
Add file which should be a disk image from a virtual machine.
The format of the disk image is auto-detected. To override this
and force a particular format use the --format option.
-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.
-d guest
--domain guest
Add all the disks from the named libvirt guest. Domain UUIDs can
be used instead of names.
-n
--dry-run
Perform a read-only "dry run" on the guest. This runs the sysprep
operation, but throws away any changes to the disk at the end.
--enable operations
Choose which sysprep operations to perform. Give a comma-separated
list of operations, for example:
--enable ssh-hostkeys,udev-persistent-net
would enable ONLY "ssh-hostkeys" and "udev-persistent-net"
operations.
If the --enable option is not given, then we default to trying most
sysprep operations (see --list-operations to show which are
enabled).
Regardless of the --enable option, sysprep operations are skipped
for some guest types.
Use --list-operations to list operations supported by a particular
version of virt-sysprep.
See "OPERATIONS" below for a list and an explanation of each
operation.
--format raw|qcow2|..
--format auto
The default for the -a option is to auto-detect the format of the
disk image. Using this forces the disk format for -a options which
follow on the command line. Using --format auto switches back to
auto-detection for subsequent -a options.
For example:
virt-sysprep--format raw -a disk.img
forces raw format (no auto-detection) for "disk.img".
virt-sysprep--format raw -a disk.img --format auto -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).
--list-operations
List the operations supported by the virt-sysprep program.
These are listed one per line, with one or more single-space-
separated fields, eg:
$ virt-sysprep--list-operations
bash-history * Remove the bash history in the guest
cron-spool * Remove user at-jobs and cron-jobs
dhcp-client-state * Remove DHCP client leases
dhcp-server-state * Remove DHCP server leases
[etc]
The first field is the operation name, which can be supplied to
--enable. The second field is a "*" character if the operation is
enabled by default or blank if not. Subsequent fields on the same
line are the description of the operation.
Before libguestfs 1.17.33 only the first (operation name) field was
shown and all operations were enabled by default.
-q
--quiet
Don't print log messages.
To enable detailed logging of individual file operations, use -x.
--selinux-relabel
--no-selinux-relabel
--selinux-relabel forces SELinux relabelling next time the guest
boots. --no-selinux-relabel disables relabelling.
The default is to try to detect if SELinux relabelling is required.
See "SELINUX RELABELLING" below for more details.
-v
--verbose
Enable verbose messages for debugging.
-V
--version
Display version number and exit.
-x Enable tracing of libguestfs API calls.
--firstboot firstboot (see "firstboot" below)
Run script(s) once next time the guest boots. You can supply the
--firstboot option as many times as needed.
--hostname hostname (see "hostname" below)
Change the hostname. If not given, defaults to
"localhost.localdomain".
--script script (see "script" below)
Run the named "script" (a shell script or program) against the
guest. The script can be any program on the host. The script's
current directory will be the guest's root directory.
Note: If the script is not on the $PATH, then you must give the
full absolute path to the script.
--scriptdir scriptdir (see "script" below)
The mount point (an empty directory on the host) used when the
"script" operation is enabled and one or more scripts are specified
using --scriptparameter(s).
Note: "scriptdir" must be an absolute path.
If --scriptdir is not specified then a temporary mountpoint will be
created.
OPERATIONS
If the --enable option is not given, then most sysprep operations are
enabled.
Use "virt-sysprep --list-operations" to list all operations for your
virt-sysprep binary. The ones which are enabled by default are marked
with a "*" character. Regardless of the --enable option, sysprep
operations are skipped for some guest types.
Operations can be individually enabled using the --enable option. Use
a comma-separated list, for example:
virt-sysprep --enable=ssh-hostkeys,udev-persistent-net [etc..]
Future versions of virt-sysprep may add more operations. If you are
using virt-sysprep and want predictable behaviour, specify only the
operations that you want to have enabled.
"*" = enabled by default when no --enable option is given.
abrt-data *
Remove the crash data generated by ABRT.
Remove the automatically generated ABRT crash data in
"/var/spool/abrt/".
bash-history *
Remove the bash history in the guest.
Remove the bash history of user "root" and any other users who have a
".bash_history" file in their home directory.
blkid-tab *
Remove blkid tab in the guest.
ca-certificates
Remove CA certificates in the guest.
crash-data *
Remove the crash data generated by kexec-tools.
Remove the automatically generated kdump kernel crash data.
cron-spool *
Remove user at-jobs and cron-jobs.
dhcp-client-state *
Remove DHCP client leases.
dhcp-server-state *
Remove DHCP server leases.
dovecot-data *
Remove Dovecot (mail server) data.
firstboot *
Add scripts to run once at next boot.
Supply one of more shell scripts (using the --firstboot option).
These are run the first time the guest boots, and then are deleted. So
these are useful for performing last minute configuration that must run
in the context of the guest operating system, for example "yum update".
Output or errors from the scripts are written to
"~root/virt-sysprep-firstboot.log" (in the guest).
Currently this is only implemented for Linux guests using either System
V init, or systemd.
flag-reconfiguration
Flag the system for reconfiguration.
Note that this may require user intervention when the guest is booted.
hostname *
Change the hostname of the guest.
This operation changes the hostname of the guest to the value given in
the --hostname parameter.
If the --hostname parameter is not given, then the hostname is changed
to "localhost.localdomain".
kerberos-data
Remove Kerberos data in the guest.
logfiles *
Remove many log files from the guest.
On Linux the following files are removed:
/root/anaconda-ks.cfg
/root/install.log
/root/install.log.syslog
/var/cache/fontconfig/*
/var/cache/gdm/*
/var/cache/man/*
/var/lib/AccountService/users/*
/var/lib/fprint/*
/var/lib/logrotate.status
/var/log/*.log*
/var/log/BackupPC/LOG
/var/log/apache2/*_log
/var/log/apache2/*_log-*
/var/log/audit/*
/var/log/audit/audit.log
/var/log/btmp*
/var/log/ceph/*.log
/var/log/chrony/*.log
/var/log/cron*
/var/log/cups/*_log
/var/log/dmesg*
/var/log/glusterfs/*glusterd.vol.log
/var/log/glusterfs/glusterfs.log
/var/log/httpd/*log
/var/log/jetty/jetty-console.log
/var/log/lastlog*
/var/log/libvirt/libvirtd.log
/var/log/libvirt/lxc/*.log
/var/log/libvirt/qemu/*.log
/var/log/libvirt/uml/*.log
/var/log/mail/*
/var/log/maillog*
/var/log/messages*
/var/log/ntp
/var/log/ppp/connect-errors
/var/log/secure*
/var/log/setroubleshoot/*.log
/var/log/spooler*
/var/log/squid/*.log
/var/log/tallylog*
/var/log/wtmp*
/var/named/data/named.run
lvm-uuids *
Change LVM2 PV and VG UUIDs.
On Linux guests that have LVM2 physical volumes (PVs) or volume groups
(VGs), new random UUIDs are generated and assigned to those PVs and
VGs.
machine-id *
Remove the local machine ID.
The machine ID is usually generated from a random source during system
installation and stays constant for all subsequent boots. Optionally,
for stateless systems it is generated during runtime at boot if it is
found to be empty.
mail-spool *
Remove email from the local mail spool directory.
net-hostname *
Remove HOSTNAME in network interface configuration.
For Fedora and Red Hat Enterprise Linux, this is removed from "ifcfg-*"
files.
net-hwaddr *
Remove HWADDR (hard-coded MAC address) configuration.
For Fedora and Red Hat Enterprise Linux, this is removed from "ifcfg-*"
files.
pacct-log *
Remove the process accounting log files.
The system wide process accounting will store to the pacct log files if
the process accounting is on.
package-manager-cache *
Remove package manager cache.
pam-data *
Remove the PAM data in the guest.
puppet-data-log *
Remove the data and log files of puppet.
random-seed *
Generate random seed for guest.
Write some random bytes from the host into the random seed file of the
guest.
See "RANDOM SEED" below.
rhn-systemid *
Remove the RHN system ID.
samba-db-log *
Remove the database and log files of Samba.
script *
Run arbitrary scripts against the guest.
The "script" module lets you run arbitrary shell scripts or programs
against the guest.
Note this feature requires FUSE support. You may have to enable this
in your host, for example by adding the current user to the "fuse"
group, or by loading a kernel module.
Use one or more --script parameters to specify scripts or programs that
will be run against the guest.
The script or program is run with its current directory being the
guest's root directory, so relative paths should be used. For example:
"rm etc/resolv.conf" in the script would remove a Linux guest's DNS
configuration file, but "rm /etc/resolv.conf" would (try to) remove the
host's file.
Normally a temporary mount point for the guest is used, but you can
choose a specific one by using the --scriptdir parameter.
Note: This is different from --firstboot scripts (which run in the
context of the guest when it is booting first time). --script scripts
run on the host, not in the guest.
smolt-uuid *
Remove the Smolt hardware UUID.
ssh-hostkeys *
Remove the SSH host keys in the guest.
The SSH host keys are regenerated (differently) next time the guest is
booted.
If, after cloning, the guest gets the same IP address, ssh will give
you a stark warning about the host key changing:
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
ssh-userdir *
Remove ".ssh" directories in the guest.
Remove the ".ssh" directory of user "root" and any other users who have
a ".ssh" directory in their home directory.
sssd-db-log *
Remove the database and log files of sssd.
udev-persistent-net *
Remove udev persistent net rules.
Remove udev persistent net rules which map the guest's existing MAC
address to a fixed ethernet device (eg. eth0).
After a guest is cloned, the MAC address usually changes. Since the
old MAC address occupies the old name (eg. eth0), this means the fresh
MAC address is assigned to a new name (eg. eth1) and this is usually
undesirable. Erasing the udev persistent net rules avoids this.
user-account
Remove the user accounts in the guest.
Remove all the user accounts and their home directories. The "root"
account is not removed.
utmp *
Remove the utmp file.
This file records who is currently logged in on a machine. In modern
Linux distros it is stored in a ramdisk and hence not part of the
virtual machine's disk, but it was stored on disk in older distros.
yum-uuid *
Remove the yum UUID.
Yum creates a fresh UUID the next time it runs when it notices that the
original UUID has been erased.
COPYING AND CLONING
Virt-sysprep can be used as part of a process of cloning guests, or to
prepare a template from which guests can be cloned. There are many
different ways to achieve this using the virt tools, and this section
is just an introduction.
A virtual machine (when switched off) consists of two parts:
configuration
The configuration or description of the guest. eg. The libvirt XML
(see "virsh dumpxml"), the running configuration of the guest, or
another external format like OVF.
Some configuration items that might need to be changed:
· name
· UUID
· path to block device(s)
· network card MAC address
block device(s)
One or more hard disk images, themselves containing files,
directories, applications, kernels, configuration, etc.
Some things inside the block devices that might need to be changed:
· hostname and other net configuration
· UUID
· SSH host keys
· Windows unique security ID (SID)
· Puppet registration
COPYING THE BLOCK DEVICE
Starting with an original guest, you probably wish to copy the guest
block device and its configuration to make a template. Then once you
are happy with the template, you will want to make many clones from it.
virt-sysprep
|
v
original guest --------> template ---------->
\------> cloned
\-----> guests
\---->
You can, of course, just copy the block device on the host using cp(1)
or dd(1).
dd dd
original guest --------> template ---------->
\------> cloned
\-----> guests
\---->
There are some smarter (and faster) ways too:
snapshot
template ---------->
\------> cloned
\-----> guests
\---->
You may want to run virt-sysprep twice, once to reset the guest (to
make a template) and a second time to customize the guest for a
specific user:
virt-sysprep virt-sysprep
(reset) (add user, keys, logos)
| |
dd v dd v
original guest ----> template ---------> copied ------> custom
template guest
· Create a snapshot using qemu-img:
qemu-img create -f qcow2 -o backing_file=original snapshot.qcow
The advantage is that you don't need to copy the original (very
fast) and only changes are stored (less storage required).
Note that writing to the backing file once you have created guests
on top of it is not possible: you will corrupt the guests.
· Create a snapshot using "lvcreate --snapshot".
· Other ways to create snapshots include using filesystems-level
tools (for filesystems such as btrfs).
Most Network Attached Storage (NAS) devices can also create cheap
snapshots from files or LUNs.
· Get your NAS to duplicate the LUN. Most NAS devices can also
duplicate LUNs very cheaply (they copy them on-demand in the
background).
· Prepare your template using virt-sparsify(1). See below.
VIRT-CLONE
A separate tool, virt-clone(1), can be used to duplicate the block
device and/or modify the external libvirt configuration of a guest. It
will reset the name, UUID and MAC address of the guest in the libvirt
XML.
virt-clone(1) does not use libguestfs and cannot look inside the disk
image. This was the original motivation to write virt-sysprep.
SPARSIFY
virt-sparsify
original guest --------> template
virt-sparsify(1) can be used to make the cloning template smaller,
making it easier to compress and/or faster to copy.
Notice that since virt-sparsify also copies the image, you can use it
to make the initial copy (instead of "dd").
RESIZE
virt-resize
template ---------->
\------> cloned
\-----> guests
\---->
If you want to give people cloned guests, but let them pick the size of
the guest themselves (eg. depending on how much they are prepared to
pay for disk space), then instead of copying the template, you can run
virt-resize(1). Virt-resize performs a copy and resize, and thus is
ideal for cloning guests from a template.
FIRSTBOOT VS SCRIPT
The two options --firstboot and --script both supply shell scripts that
are run against the guest. However these two options are significantly
different.
--firstboot script uploads the file "script" into the guest and
arranges that it will run, in the guest, when the guest is next booted.
(The script will only run once, at the "first boot").
--script script runs the shell "script" on the host, with its current
directory inside the guest filesystem.
If you needed, for example, to "yum install" new packages, then you
must not use --script for this, since that would (a) run the "yum"
command on the host and (b) wouldn't have access to the same resources
(repositories, keys, etc.) as the guest. Any command that needs to run
on the guest must be run via --firstboot.
On the other hand if you need to make adjustments to the guest
filesystem (eg. copying in files), then --script is ideal since (a) it
has access to the host filesystem and (b) you will get immediate
feedback on errors.
Either or both options can be used multiple times on the command line.
SECURITY
Although virt-sysprep removes some sensitive information from the
guest, it does not pretend to remove all of it. You should examine the
"OPERATIONS" above and the guest afterwards.
Sensitive files are simply removed. The data they contained may still
exist on the disk, easily recovered with a hex editor or undelete tool.
Use virt-sparsify(1) as one way to remove this content. See also the
scrub(1) command to get rid of deleted content in directory entries and
inodes.
RANDOM SEED
(This section applies to Linux guests only)
The virt-sysprep "random-seed" operation writes a few bytes of
randomness from the host into the guest's random seed file.
If this is just done once and the guest is cloned from the same
template, then each guest will start with the same entropy, and things
like SSH host keys and TCP sequence numbers may be predictable.
Therefore you should arrange to add more randomness after cloning from
a template too, which can be done by just enabling the "random-seed"
operation:
cp template.img newguest.img
virt-sysprep--enable random-seed -a newguest.img
SELINUX RELABELLING
(This section applies to Linux guests using SELinux only)
If any new files are created by virt-sysprep, then virt-sysprep touches
"/.autorelabel" so that these will be correctly labelled by SELinux the
next time the guest is booted. This process interrupts boot and can
take some time.
You can force relabelling for all guests by supplying the
--selinux-relabel option.
You can disable relabelling entirely by supplying the
--no-selinux-relabel option.
WINDOWS 8
Windows 8 "fast startup" can prevent virt-sysprep from working. See
"WINDOWS HIBERNATION AND WINDOWS 8 FAST STARTUP" in guestfs(3).
SHELL QUOTING
Libvirt guest names can contain arbitrary characters, some of which
have meaning to the shell such as "#" and space. You may need to quote
or escape these characters on the command line. See the shell manual
page sh(1) for details.
EXIT STATUS
This program returns 0 on success, or 1 if there was an error.
SEE ALSOguestfs(3), guestfish(1), virt-clone(1), virt-rescue(1),
virt-resize(1), virt-sparsify(1), virsh(1), lvcreate(8), qemu-img(1),
scrub(1), http://libguestfs.org/, http://libvirt.org/.
AUTHORS
Richard W.M. Jones http://people.redhat.com/~rjones/
Wanlong Gao, Fujitsu Ltd.
COPYRIGHT
Copyright (C) 2011-2012 Red Hat Inc.
Copyright (C) 2012 Fujitsu Ltd.
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.
libguestfs-1.20.4 2013-03-12 virt-sysprep(1)
