XEN-CREATE-IMAGE(8) Perl Programmers Reference Guide XEN-CREATE-IMAGE(8)
NAME
xen-create-image - Easily create new Xen instances with networking and
OpenSSH.
SYNOPSIS
Help Options:
--help Show the help information for this script.
--manual Read the manual, and examples, for this script.
--verbose Show useful debugging information.
--version Show the version number and exit.
Size / General options:
--accounts Copy all non-system accounts to the guest image
--admins Specify that some administrators should be created for
this image, using xen-shell.
--boot Boot the new instance after creating it.
--cache Cache .deb files on the host when installing the new guest
with the debootstrap tool.
--config Read the specified file in addition to the global
configuration file.
--copy-cmd NOP: Ignored.
--debootstrap-cmd NOP: Ignored.
--force Force overwriting existing images.
This will remove existing images or LVM volumes which match
those which are liable to be used by the new invocation.
--fs Specify the filesystem type to use for the new guest.
Valid choices are ’ext2’, ’ext3’, ’reiserfs’, or ’xfs’.
--image Specify whether to create "sparse" or "full" disk images.
Full images are mandatory when using LVM, so this setting
is ignored in that case.
--image-dev Specify a physical/logical volume for the disk image.
--initrd Specify the initial ramdisk
If an image is specified it must exist.
--keep Don’t delete our images if installation fails.
--kernel Set the path to the kernel to use for domU.
If a kernel is specified it must exist.
--memory Setup the amount of memory allocated to the new instance.
--modules Set the path to the kernel modules to use for domU.
If modules are specified they must exist.
--output Specify the output directory to create the xen configuratoin
file within.
--install Specify whether to install the guest system or not.
--hooks Specify whether to run hooks after the image is created.
--no-hosts Don’t touch /etc/hosts on the dom0.
--partitions Use a specific partition layout configuration file.
Not supported with the image-dev and swap-dev options.
Parameters fs, size, swap and noswap are ignored when
using this option.
--passwd Ask for a root password during setup.
NOTE: This is done interactively.
--role Run the specified role script(s) post-install.
Role scripts are discussed later in this manpage.
--role-args Pass the named string literally to any role script.
This is useful for site-specific roles.
--roledir Specify the directory which contains the role scripts.
This defaults to /etc/xen-tools/role.d/
--size Set the size of the primary disk image.
--tar-cmd NOP: Ignored.
--extension Specify the suffix to give the Xen configuration file.
--swap Set the size of the swap partition.
--swap-dev Specify a physical/logical volume for swap usage.
--noswap Do not create a swap partition.
When this option is used the system will not have a swap
entry added to its /etc/fstab file either.
--ide Use IDE names for virtual devices (i.e. hda not sda)
Installation options:
--arch Pass the given architecture to debootstrap, rinse,
or rpmstrap when installing the system. This argument
is ignored for other install methods.
--dist Specify the distribution you wish to install.
--install-method Specify the installation method to use.
--install-source Specify the source path to use when installing via
a copy or tarball installation.
--mirror Setup the mirror to use when installing via debootstrap.
--template Specify which template file to use when creating the
Xen configuration file.
Networking options:
--dhcp The guest will be configured to fetch its networking
details via DHCP.
--gateway Setup the network gateway for the new instance.
--ip Setup the IP address of the machine, multiple IPs
are allowed. When specifying more than one IP the
first one is setup as the "system" IP, and the additional
ones are added as aliases.
Note that Xen 3.x supports a maximum of three vif statements
per guest.
This option conflicts with --dhcp.
--mac Specify the MAC address to use for a given interface.
This is only valid for the first IP address specified, or
for DHCP usage. (ie. you can add multiple --ip flags,
but the specific MAC address will only be used for the
first interface.)
--netmask Setup the netmask for the new instance.
--broadcast Setup the broadcast address for the new instance.
Mandatory options:
--dir Specify where the output images should go.
Subdirectories will be created for each guest
If you do not wish to use loopback images specify --lvm
or --evms. (These three options are mutually exclusive.)
--lvm Specify the volume group to save images within.
If you do not wish to use LVM specify --dir or --evms.
(These three options are mutually exclusive.)
--evms Specify the container to save images within, i.e. ’--evms
lvm2/mycontainer’. If you do not wish to use EVMS specify
--dir or --lvm. (These three options are mutually exclusive.)
--hostname Set the hostname of the new guest system.
Ideally this will be fully-qualified since several
of the hook scripts will expect to be able to parse
a domain name out of it for various purposes.
NOTES
This script is a wrapper around three distinct external tools which
complete various aspects of the new system installation.
xt-install-image Install a new distribution.
xt-customize-image Run a collection of hook scripts to customise the
freshly installed system.
xt-create-xen-config Create a Xen configuration file in so that xm can
start the new domain.
The result of invoking these three scripts, and some minor glue between
them, is a simple means of creating new Xen guest domains.
DESCRIPTION
xen-create-image is a simple script which allows you to create new
Xen instances easily. The new image will be given two volumes. These
volumes will be stored upon the host as either loopback files, or
LVM logical volumes:
1. An image for the systems root disk.
2. An image for the systems swap device.
The new virtual installations will be configured with networking,
have OpenSSH installed upon it, and have most of its basic files
setup correctly.
If you wish you can configure arbitary partitioning schemes, rather
than being restricted to just the two standard volumes. For more
details on this please see the later section in this manual "PARTITIONING".
CONFIGURATION
To reduce the length of the command line each of the supported options
may be specified inside a configuration file.
The global configuration file read for options is:
/etc/xen-tools/xen-tools.conf
The configuration file may contain comments which begin with the
hash ’#’ character. Otherwise the format is ’key = value’.
A sample configuration file would look like this:
#
# Output directory. Images are stored beneath this directory, one
# subdirectory per hostname.
#
dir = /home/xen
#
# LVM users should disable the ’dir’ setting above, and instead
# specify the name of the volume group to use.
#
# lvm = myvolume
#
# EVMS users should disable the dir setting above and instead specify
# a container. For example, if you have an lvm2 container named box,
# put lvm2/box. This is how it is named in the evms interface.
#
# Warning... this has not been tested with anything but lvm2 but should
# be generalizable.
#
# evms= lvm2/myvolume
#
# Disk and Sizing options.
#
size = 2Gb # Disk image size.
image = full # Allocate the full disk size immediately.
memory = 128Mb # Memory size
swap = 128Mb # Swap size
fs = ext3 # use EXT3 filesystems
dist = sarge # Default distribution to install.
#
# Kernel options.
#
kernel = /boot/vmlinuz-‘uname -r‘
initrd = /boot/initrd.img-‘uname -r‘
#
# Networking options.
#
gateway = 192.168.1.1
broadcast = 192.168.1.255
netmask = 255.255.255.0
#
# Installation method:
# One of "copy", "debootstrap", "rinse", "rpmstrap", or "tar".
#
install-method = debootstrap
Using this configuration file a new image may be created with the
following command:
xen-create-image --hostname=vm03.my.flat --ip=192.168.1.201
This makes use of loopback images stored beneath /home/xen and
will be installed via the debootstrap command.
NETWORKING AUTO-SETUP
We’ve already seen how the "gateway" and "netmask" options can
be used to specify the networking options of the freshly created
Xen guests.
One other useful shortcut is the use of an automatic IP address.
You can specify ’--ip=auto’ and the system will choose and use
an IP address from those listed in /etc/xen-tools/ips.txt.
For example if you wished to have Xen guests automatically
take an address from the range 192.168.1.100-192.168.1.200 you
would first prepare the system by running this:
rm /etc/xen-tools/ips.txt
for i in $(seq 100 200) ; do echo 192.168.1.$i >> /etc/xen-tools/ips.txt ; done
Now you can create a guest with the command:
xen-create-image --ip=auto --hostname=blah [--dist=...]
The first time this ran the machine would recieve an IP address
from the pool which we’ve created. This IP would be marked as used,
and would no longer be available. If all the IP addresses are taken
then the system will fail.
PARTITIONING
By default all new guests are created with two "volumes", one
for the root filesystem and one for the new system’s swap.
If you wish you may specify an alternative partitioning scheme.
Simply create a file inside the directory /etc/xen-tools/partitions.d/
specifying your partition layout. (Use the existing file "sample-server"
as a template).
Now when you create a new image specify the name of this file with as
an argument to the --partition option.
XEN CONFIGURATION FILE
Once a new image has been created an appropriate configuration file
for Xen will be saved in the directory /etc/xen by default. However
you may change the output directory with the --output flag.
The configuration file is built up using the template file
/etc/xen-tools/xm.tmpl - which is a file processed via
the Text::Template perl module.
If you wish to modify the files which are generated please make your
changes to that input file.
Alternatively you can create multiple configuration files and
specify the one to use with the --template option.
LOOPBACK EXAMPLES
The following will create a 2Gb disk image, along with a 128Mb
swap file with Debian Sarge setup and running via DHCP.
xen-create-image --size=2Gb --swap=128Mb --dhcp \
--dir=/home/xen --hostname=vm01.my.flat
This next example sets up a host which has the name ’vm02.my.flat’ and
IP address 192.168.1.200, with the gateway address of 192.168.1.1
xen-create-image --size=2Gb --swap=128Mb \
--ip=192.168.1.200 \
--netmask=255.255.255.0
--gateway=192.168.1.1 \
--dir=/home/xen --hostname=vm02.my.flat
The directory specified for the output will be used to store the volumes
which are produced. To avoid clutter each host will have its images
stored beneath the specified directory, named after the hostname.
For example the images created above will be stored as:
$dir/domains/vm01.my.flat/
$dir/domains/vm01.my.flat/disk.img
$dir/domains/vm01.my.flat/swap.img
$dir/domains/vm02.my.flat/
$dir/domains/vm02.my.flat/disk.img
$dir/domains/vm02.my.flat/swap.img
The ’/domains/’ subdirectory will be created if necessary.
LVM EXAMPLE
If you wish to use an LVM volume group instead of a pair of loopback
images as shown above you can instead use the --lvm argument to
specify one.
xen-create-image --size=2Gb --swap=128Mb --dhcp \
--lvm=myvolumegroup --hostname=vm01.my.flat
The given volume group will have two new logical volumes created within it:
${hostname}-swap
${hostname}-disk
The disk image may be mounted, as you would expect, with the following
command:
mkdir -p /mnt/foo
mount /dev/myvolumegroup/vm01.my.flat-disk /mnt/foo
EVMS EXAMPLE
If you wish to use an EVMS storage container instead of a pair of loopback
images as shown above you can instead use the --evms argument to
specify one. The below example assumes an lvm2 container.
xen-create-image --size=2Gb --swap=128Mb --dhcp \
--evms=lvm2/myvolumegroup --hostname=vm01.my.flat
The given storage container will have two new EVMS volumes created within it:
${hostname}-swap
${hostname}-disk
The disk image may be mounted, as you would expect, with the following
command:
mkdir -p /mnt/foo
mount /dev/evms/vm01.my.flat-disk /mnt/foo
INSTALLATION METHODS
The new guest images may be installed in several different ways:
1. Using the debootstrap command, which must be installed and present.
2. Using the rpmstrap command, which must be installed and present.
3. using the rinse command, which must be installed and present.
4. By copying an existing installation.
5. By untarring a file containing a previous installation.
These different methods can be selected by either the command line
arguments, or settings in the configuration file. Only one installation
method may be specified at a time; they are mutually-exclusive.
INSTALLATION SPEEDUPS
After performing your first installation you can customize it, or
use it untouched, as a new installation source. By doing this you’ll
achieve a significant speedup, even above using the debootstrap caching
support.
There are two different ways you can use the initial image as source
for a new image:
1. By tarring it up and using the tar-file as an installation source.
2. By mounting the disk image of the first system and doing a literal copy.
Tarring up a pristine, or customised, image will allow you to install
with a command such as:
xen-create-image --size=2Gb --swap=128Mb --dhcp \
--lvm=myvolumegroup --hostname=vm01.my.flat \
--install-method=tar --install-source=/path/to/tar.file.tar
The advantage of the tarfile approach is that you’ll not need to
keep a disk image mounted if you were to use the --copy argument
to create a new image using the old one as source:
xen-create-image --size=2Gb --swap=128Mb --dhcp \
--lvm=myvolumegroup --hostname=vm01.my.flat \
--install-method=copy --install-source=/path/to/copy/from
DEBOOTSTRAP CACHING
When installing new systems with the debootstrap tool there is
a fair amount of network overhead.
To minimize this the .deb files which are downloaded into the
new instance are cached by default upon the host, in the directory
/var/cache/apt/archives.
When a new image is created these packages are copied into the new
image - before the debootstrap process runs - this should help avoid
expensive network reading.
If you wish to clean the cache upon the host you may do so with
apt-get, as you’d expect:
apt-get clean
(This feature can be disabled with the command line flag --cache=no,
or by the matching setting in the configuration file.)
ROLES
Currently there are some roles scripts included which work for
the Debian Sarge and Etch distrubtions only. They are included
primarily as examples of the kind of things you could accomplish.
The supplied scripts are:
builder Setup the new virtual images with commonly used packages for
rebuilding Debian packages from their source.
gdm Install an X11 server, using VNC and GDM
minimal Customise the generated images to remove some packages.
xdm Install an X11 server, using VNC and XDM
If you’d like to include your own role scripts you’ll need to
create a file in /etc/xen-tools/role.d, and then specify the
name of that file with "--role=filename". Additionally you
may pass options to your role-script with the --role-args
flag.
For example the script /etc/xen-tools/role.d/gdm would be used
by executing with "--role=gdm".
Role scripts are invoked with the directory containing the
installed system as their first argument, and anything passed
as a role-arg will be passed allong as additional arguments.
NOTE: Multiple role scripts may be invoked if you separate their
names with commas.
THE SKELETON DIRECTORY
Any files present in the directory /etc/xen-tools/skel will be copied
across to each new guest image. The role of this directory is analogous
to the /etc/skel directory.
A typical use for this would be to copy a public key across to each
new system. You could do this by running:
mkdir -p /etc/xen-tools/skel/root/.ssh
chmod -R 700 /etc/xen-tools/skel/root
cp /root/.ssh/id_rsa.pub /etc/xen-tools/skel/root/.ssh/authorized_keys2
chmod 644 /etc/xen-tools/skel/root/.ssh/authorized_keys2
AUTHOR
Steve
--
http://www.steve.org.uk/
LICENSE
Copyright (c) 2005-2007 by Steve Kemp. All rights reserved.
This module is free software; you can redistribute it and/or modify it
under the same terms as Perl itself. The LICENSE file contains the
full text of the license.
4.1 2009-02-06 XEN-CREATE-IMAGE(8)
