=encoding utf8 =head1 NAME virt-sysprep - Reset or unconfigure a virtual machine so clones can be made =head1 SYNOPSIS virt-sysprep [--options] -d domname virt-sysprep [--options] -a disk.img [-a disk.img ...] =head1 DESCRIPTION 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 required. Virt-sysprep is a simple shell script, allowing easy inspection or customization by the system administrator. Virt-sysprep modifies the guest or disk image I. The guest must be shut down. If you want to preserve the existing contents of the guest, you I. See L below. "Sysprep" stands for "system preparation" tool. The name comes from the Microsoft program C which is used to unconfigure Windows machines in preparation for cloning them. Having said that, virt-sysprep does I currently work on Microsoft Windows guests. We plan to support Windows sysprepping in a future version, and we already have code to do it. =head1 OPTIONS =over 4 =item B<--help> Display brief help. =item B<-a> file =item B<--add> file Add I 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 I<--format=..> option. =item B<-c> URI =item B<--connect> URI If using libvirt, connect to the given I. If omitted, then we connect to the default libvirt hypervisor. If you specify guest block devices directly (I<-a>), then libvirt is not used at all. =item B<-d> guest =item B<--domain> guest Add all the disks from the named libvirt guest. Domain UUIDs can be used instead of names. =item B<--enable=...> Choose which sysprep operations to perform. Give a comma-separated list of operations, for example: --enable=ssh-hostkeys,udev-persistent-net would enable ONLY C and C operations. If the I<--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 I<--list-operations> to list operations supported by a particular version of virt-sysprep. See L below for a list and an explanation of each operation. =item B<--format=raw|qcow2|..> =item B<--format> The default for the I<-a> option is to auto-detect the format of the disk image. Using this forces the disk format for I<-a> options which follow on the command line. Using I<--format> with no argument switches back to auto-detection for subsequent I<-a> options. For example: virt-sysprep --format=raw -a disk.img forces raw format (no auto-detection) for C. virt-sysprep --format=raw -a disk.img --format -a another.img forces raw format (no auto-detection) for C and reverts to auto-detection for C. 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). =item B<--hostname> newhostname Change the hostname. See the L operation below. If not given, defaults to C. =item B<--list-operations> List the operations supported by the virt-sysprep program. =item B<-v> =item B<--verbose> Enable verbose messages for debugging. =item B<-V> =item B<--version> Display version number and exit. =item B<-x> Enable tracing of libguestfs API calls. =back =head1 OPERATIONS If the I<--enable> option is I given, then all sysprep operations in the list below are enabled, although some are skipped depending on the type of guest. Operations can be individually enabled using the I<--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 I<--list-operations>. =head2 hostname This changes the hostname of the guest to the value given in the I<--hostname> parameter. If the I<--hostname> parameter is not given, then the hostname is changed to C. =head2 net-hwaddr Remove HWADDR (hard-coded MAC address) configuration. For Fedora and Red Hat Enterprise Linux, this is removed from C files. =head2 ssh-hostkeys This erases 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! =head2 udev-persistent-net This erases 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. =head1 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: =over 4 =item I The configuration or description of the guest. eg. The libvirt XML (see C), the running configuration of the guest, or another external format like OVF. Some configuration items that might need to be changed: =over 4 =item * name =item * UUID =item * path to block device(s) =item * network card MAC address =back =item I 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: =over 4 =item * hostname and other net configuration =item * UUID =item * SSH host keys =item * Windows unique security ID (SID) =item * Puppet registration =back =back =head2 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 L or L. dd dd original guest --------> template ----------> \------> cloned \-----> guests \----> There are some smarter (and faster) ways too: =over 4 =item * snapshot 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: L (with the I option), L (I<--snapshot> option). Some filesystems (such as btrfs) and most Network Attached Storage devices can also create cheap snapshots from files or LUNs. =item * Get your NAS to snapshot and/or duplicate the LUN. =item * Prepare your template using L. See below. =back =head2 VIRT-CLONE A separate tool, L, 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. L does not use libguestfs and cannot look inside the disk image. This was the original motivation to write virt-sysprep. =head2 SPARSIFY virt-sparsify original guest --------> template L 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 C
). =head2 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 L. Virt-resize performs a copy and resize, and thus is ideal for cloning guests from a template. =head1 SHELL QUOTING Libvirt guest names can contain arbitrary characters, some of which have meaning to the shell such as C<#> and space. You may need to quote or escape these characters on the command line. See the shell manual page L for details. =head1 EXIT STATUS This program returns 0 on success, or 1 if there was an error. =head1 SEE ALSO L, L, L, L, L, L, L, L, L, L, L. =head1 AUTHOR Richard W.M. Jones L =head1 COPYRIGHT 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., 675 Mass Ave, Cambridge, MA 02139, USA.