Provided by: libguestfs-tools_1.14.8-1_amd64 bug


       virt-sysprep - Reset or unconfigure a virtual machine so clones can be made


        virt-sysprep [--options] -d domname

        virt-sysprep [--options] -a disk.img [-a disk.img ...]


       Virt-sysprep "resets" or "unconfigures" 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.  Each step can be enabled or disabled as

       Virt-sysprep is a simple shell script, allowing easy inspection or customization by the
       system administrator.

       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 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


           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

           Choose which sysprep operations to perform.  Give a comma-separated list of
           operations, for example:


           would enable ONLY "ssh-hostkeys" and "udev-persistent-net" operations.

           If the --enable option is not given, then we default to trying all possible sysprep
           operations.  But some sysprep operations are skipped for some guest types.

           Use --list-operations to list operations supported by a particular version of virt-

           See "OPERATIONS" below for a list and an explanation of each operation.

           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 with no argument 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 -a another.img

           forces raw format (no auto-detection) for "disk.img" and reverts to auto-detection for

           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).

       --hostname newhostname
           Change the hostname.  See the "hostname" operation below.  If not given, defaults to

           List the operations supported by the virt-sysprep program.

           --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.

           Enable verbose messages for debugging.

           Display version number and exit.

       -x  Enable tracing of libguestfs API calls.


       If the --enable option is not given, then all sysprep operations are enabled, although
       some are skipped depending on the type of guest.

       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..]

       To list the operations supported by the current version of virt-sysprep, use

       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.

       Remove user at-jobs and cron-jobs.

       Remove DHCP client leases.

       Remove DHCP server leases.

       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

       Remove many log files.

       Remove email from the local mail spool directory.

       Remove HWADDR (hard-coded MAC address) configuration.  For Fedora and Red Hat Enterprise
       Linux, this is removed from "ifcfg-*" files.

       Write some random bytes from the host into the random seed file of the guest.

       See "RANDOM SEED" below.

       Remove the RHN system ID.

       Remove the Smolt hardware UUID.

       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:


       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.

       Remove the utmp file.

       This 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.

       Remove the yum UUID.

       Yum creates a fresh UUID the next time it runs when it notices that the original UUID has
       been erased.


       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:

           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

           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

       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.

        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:


                           template ---------->
                                       \------> cloned
                                        \-----> guests

           Use the block device as a backing file and create a snapshot on top for each guest.
           The advantage is that you don't need to copy the block device (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.

           Tools that can do this include: qemu-img(1) (with the create -f qcow2 -o backing_file
           option), lvcreate(8) (--snapshot option).  Some filesystems (such as btrfs) and most
           Network Attached Storage devices can also create cheap snapshots from files or LUNs.

       ·   Get your NAS to snapshot and/or duplicate the LUN.

       ·   Prepare your template using virt-sparsify(1).  See below.

       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.

        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").

                       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.


       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
       implementation of the operations in the shell script.  You should also examine the guest

       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.

       (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

       (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.


       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.


       This program returns 0 on success, or 1 if there was an error.


       guestfs(3), guestfish(1), virt-clone(1), virt-rescue(1), virt-resize(1), virt-sparsify(1),
       virsh(1), lvcreate(8), qemu-img(1), scrub(1), <>,


       Richard W.M. Jones <>


       Copyright (C) 2011 Red Hat Inc.

       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.