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Install and setup Xen on Debian 4.0 Etch and 5.0 Lenny

by Pierre-Yves Landuré last modified 2011-03-06 20:52

Xen is a GPLed virtualization solution available in Debian repositories. This article help you to create a coherent Xen installation, with backups and minimum security enhancements. This guide fits my vision of a Xen setup. If it does not fit yours, you are free to adapt it to your needs, or to not use it.

For information

In this guide, i use the term "virtual host". Be aware that Xen use its own terminology. In a Xen setup, instanciated (aka. started) virtual hosts are called "Domains".

Once your computer configured for Xen, all the operating systems run in "domains". The original operating system, where the Xen's control tools are installed, is called "dom0" (for domain No zero). All the guest operating systems are said to be installed in a "domU" (for User domain).

As i'm a little lazy (well, yeah... very lazy), i don't want to endure this mind twisting, and i will mainly use the "virtual host" term in this guide. So, if you read this guide, don't by angry at me because of the terms i use.


This guide use the capabilities of LVM. If you don't know what LVM is, and if you want to install it on your computer, i encourage you to read this article:

A simple introduction to working with LVM

Source: Thanks to Steve Kemp for his article on Debian Administration.

Installing on Debian 5.0 Lenny

First, we install the Xen hypervisor, the Xen kernel for the Dom0, and some more tools:

/usr/bin/apt-get install xen-hypervisor-i386 linux-image-2.6-xen-686 linux-headers-2.6-xen-686 \
                         xen-utils-3.2-1 xen-tools bridge-utils

Important: If you use a 64 bits version of Debian, use this command line:

/usr/bin/apt-get install xen-hypervisor-amd64 linux-image-2.6-xen-amd64 linux-headers-2.6-xen-amd64 \
                         xen-utils-3.2-1 xen-tools bridge-utils

Once this done, we reboot in order to use the new kernel:


Installing on Debian 4.0 Etch

First, we install the Linux kernel needed by Xen and a patched C library for Xen to work properly:

/usr/bin/apt-get install linux-image-2.6-xen-vserver-686 linux-headers-2.6-xen-vserver-686 libc6-xen \
                         xen-hypervisor-3.0.3-1-i386-pae xen-tools bridge-utils

Important: If you use a 64 bits version of Debian Etch, use the following command line:

/usr/bin/apt-get install linux-image-2.6-xen-vserver-amd64 linux-headers-2.6-xen-vserver-amd64 \
                         xen-hypervisor-3.0.3-1-amd64 xen-tools bridge-utils

Note: If your CPU has the needed instructions set, and if you want to install unmodified operating systems (such as Windows XP), you need to install some more packages:

/usr/bin/apt-get install xen-ioemu-3.0.3-1

Once this done, we restart the computer in order to use the new kernel:


Virtualized Ubuntu 8.04 Hardy Heron and Debian 5.0 Lenny operating systems on Debian 4.0 Etch

To be able to use Ubuntu 8.04 Hardy Heron and Debian 5.0 Etch in the DomU from a Debian 4.0 Dom0, we need to add some more tools (basically, a debootstrap backport) :

if [ "$(/bin/cat /etc/debian_version)" = "4.0" ]; then
  /bin/ln -s ubuntu.d /usr/lib/xen-tools/hardy.d
  /bin/ln -s debian.d /usr/lib/xen-tools/lenny.d
  /usr/bin/wget \
  /usr/bin/dpkg -i /tmp/debootstrap_1.0.10_all.deb

Xen related errors

Kernel panic during domain creation

In order to avoid a kernel panic of the host computer (dom0) when starting a virtual host (domU), we need to limit the number of CPU available for the dom0. This is done by this command line:

/bin/sed -i -e 's/^[# ]*\((dom0-cpus\).*\().*\)$/\1 1\2/' \

Source: Thanks to Gerald Hochegger for his e-mail Bug#410807: workaround: linux-image-2.6.18-4-xen-amd64: Kernel BUG at drivers/xen/core/evtchn.c:481

Connexion problems to the virtual hosts networks

After a while, and with a certain amount of created virtual hosts, a network bug appear. One of the symptoms of this bug is the presence of the following messages in the syslog of the host computer (dom0):

xen_net: Memory squeeze in netback driver.

The correction of this problem need a restart of the computer. First, you need to edit the Grub configuration file in order to limit the amount of RAM allocated to the dom0 at boot time:

/bin/sed -i -e 's/\(xenhopt=.*\)/\1dom0_mem=256M/' \

Apply this change to all the kernels listed by Grub:


And apply the same amount of RAM to the minimum memory available to the dom0:

/bin/sed -i -e 's/^[# ]*\((dom0-min-mem\).*\().*\)$/\1 256\2/' \

To make this changes effective, you need to restart your computer:


Source: Thanks to Crucial Paradigm for their article Xen Bug: xen_net: Memory squeeze in netback driver (32bit PAE).

Errors /dev/mem: mmap: Bad address in the virtual hosts (domU)

This error is thrown by dmidecode. dmidecode try to access low level hardware informations in order to guess a adapted default configuration. This can not work in Xen guest computers, and can be ignored.

Source: Thanks to MingsVille for the reply to the question When doing an apt-get or aptitude update I see an error like /dev/mem: mmap: Bad address; is this a cause for concern ? that he found in the technical informations for BitFolk VPS customers.

Network configuration

Xen offers several network modes. This guide support 2 of them. For a short summary:

    • Mode bridge: the virtual hosts are seen on the local network of the Xen host. They are available from other computers than the Xen host. It is the configuration to use if your host computer (dom0) is part of a local area network.
      Note : This guide is now bridge ready. It was not in its previous versions.
  • Mode NAT: the virtual hosts are on a virtual local network. They are only available for the Xen host, unless a NAT rule is set. It is the configuration to use if your computer (dom0) is not part of a local network (dedicated server, ...)

Choosing the Xen network mode

If you want your virtual hosts to be protected by a NAT firewall, which I recommend unless you know what you are doing, choose the NAT network mode :


Note : If you are wanting to use the bridge mode (not recommended if your dom0 is directly available on the internet), you only need to setup this environment variable :


Configuring the Xen network

The first step is to disable the previous network configuration:

/bin/sed -i -e 's/^(network-script .*).*$/# \0/' \
            -e 's/^(vif-script .*).*$/# \0/' \

We now enable the network configuration that we choosed before :

/bin/sed -i -e "s/^#[ ]*\\((network-script.*network-${XEN_NETWORK_MODE}).*\\)\$/\\1/" \
            -e "s/^#[ ]*\\((vif-script.*vif-${XEN_NETWORK_MODE}).*\\)\$/\\1/" \

We restart the Xen daemon to enable the new network configuration:

/etc/init.d/xend restart

Detecting Dom0 IP address

In order for this guide to work properly, we need to know the IP address of the Dom0. If you are using NAT networking, the IP is, but if you are using bridge networking, we need to use the IP address of the physical interface (here, we suppose that the physical interface is etch0) :

if [ $(/bin/grep "^[^#]*bridge" /etc/xen/xend-config.sxp | /usr/bin/wc --lines) -gt 0 ]; then
  MAINDOM_IP=$(/sbin/ifconfig eth0 | /bin/grep "inet " | /bin/sed -e 's/^.*inet [^:]*:\([^ ]*\) .*$/\1/')

You can check the detected IP address with this command :

/bin/echo "The IP address of this server for the DomU is: ${MAINDOM_IP}"

Note: If the guessed address is not correct, you can use this command line to correct it:


Configuring the host computer (dom0) SMTP server

Warning: The goal of this part of this Xen guide is to configure the SMTP server of the host computer (dom0). If your STMP server is already configured, the following command lines will replace your configuration. If this is a problem for you, and if you choosed NAT mode, please make your SMTP server listen on the IP, and accept to relay mail from

It is very important to watch the logs and the security updates of your servers. Many tools such as cron-apt, logwatch, rkhunter do this job for you. They send daily reports by e-mail. But a working SMTP server is needed for this tools to be useful. If you are used to SMTP servers configuration, i think that this part of the guide will be of small interest for you, but if it is not the case, we will setup a SMTP serveeer in the host computer (dom0) that will handle the e-mails from the guest computers (domU) created with this guide.

First, we setup the mail domain of our SMTP server. It is often the host name of the server. On a OVH server, it is quite easy to know it:

/bin/echo $HOSTNAME | /usr/bin/tee /etc/mailname

Note: This mail domain must be a valid and working hostname (ie. you must be able to ping this mail domain from any computer of the internet).

We now input the e-mail address to witch are sent the guest computers root mails:

Note: You should use your usual e-mail address.

We apply this configuration:

/bin/sed -i -e '/^root/d' /etc/aliases
echo "root: ${ADMIN_EMAIL}" | /usr/bin/tee -a /etc/aliases

Install the Exim 4 configuration file with the needed configuration for this guide:

/bin/mkdir --parent /etc/exim4
/usr/bin/wget \

Note: This configuration match a dedicated server from a provider like OVH. If you host your server at home, you should adapt this configuration to your Internet Service Provider. I will not give an example for a configuration that fit this need, since i have no use of it. But if you want to contribute to this guide, you can send me an email with the needed configuration by using the "contact" link at the top right of this site XD.


Update the Exim 4 configuration in order to accept incoming emails from the domU:

MAINDOM_RANGE=$(/bin/echo ${MAINDOM_IP} | /bin/sed -e 's/\(.*\)\.[0-9]*/\1/')
/bin/sed -i -e "s|dc_local_interfaces=.*\$|dc_local_interfaces=';${MAINDOM_IP}'|" \
            -e "s|dc_relay_nets=.*\$|dc_relay_nets='${MAINDOM_RANGE}.0/24'|" \


Install Exim 4:

/usr/bin/apt-get install exim4

Note: if Exim 4 is already installed on your server, please update its configuration with the command:

/etc/init.d/exim4 restart

Test the configuration. In order to do this, install mailx:

/usr/bin/apt-get install mailx

And use this command line to send an email to the root user:

/bin/echo "test" | /usr/bin/mail -s "test" root

Solving problems

If Exim 4 is configured right, you should recieve an email with "test" as subject. If after some time you have not received this email, check the result of this command:


and the content of the Exim log file:

tail -n 250 /var/log/exim4/mainlog


If the encountered error is something like :

root@my-hostname: Unrouteable address

The error come from a incoherence between the environment variable ${HOSTNAME} and the content of the /etc/hosts file. In order to solve this problem, the content of the /etc/mailname file shoud be "". This command line has for goal to do this (but provide no success garanty) :

/bin/grep "${HOSTNAME}" /etc/hosts | /usr/bin/cut --field=2 | /usr/bin/tee /etc/mailname

Update the Exim 4 configuration :

/etc/init.d/exim4 restart

Delete the frozen messages from the Exim 4 mail queue:

mailq | grep frozen | sed -e 's/.* \(.\{6\}-.\{6\}-.\{2\}\) .*/\1/' | xargs exim4 -Mrm

Again, test your Exim 4 configuration by sending a "test" e-mail :

/bin/echo "test" | /usr/bin/mail -s "test" root

With luck, this new configuration work. To be assured of this, check that this command show a empty mail queue :



Configuring backups

This guide setup a complex backup infrastructure based on the use of the Backup Manager tool. Your guest computers (domU) will centralize their backups in the /var/archives folder of the host computer (dom0). We need to create this folder:

/bin/mkdir /var/archives
/bin/chown root:backup /var/archives
/bin/chmod ug+rwx /var/archives

Once this done, your host computer (dom0) can store the backup of the guest operating systems (domU).

Installing Backup Manager

Your backup configuration is not complete, since for the moment only the guest OS (domU) are backuped. You also need to backup the host computer (dom0). In order to do this, i encourage you to use my guide:

Install and configure Backup Manager on Debian 4.0 Etch

Once Backup Manager installed, we need to configure it so that the /var/archives folder can be writen by the guest OS (domU), and domU archives be purged at the same time that dom0 archives :

/bin/sed -i -e 's/[#]*\(.*BM_REPOSITORY_GROUP=\).*$/\1"backup"/' \
            -e 's/[#]*\(.*BM_REPOSITORY_CHMOD=\).*$/\1"770"/' \
            -e 's/[#]*\(.*BM_ARCHIVE_STRICTPURGE=\).*$/\1"false"/' \

I strongly encourage you to copy your backups to another server with the help of Backup Manager. If you use a OVH server, this company provides a FTP space of the size of your server hard drives to you.

Configuring virtual guest creation by Xen Tools

Default configuration

By default, Xen Tools is configured to create Debian 3.1 Sarge based guest computers. We will change this. Use this command line to setup Xen Tools to create Debian 4.0 Etch or 5.0 Lenny guest computers by default (depending on the Dom0 distribution):

if [ "$(/bin/cat /etc/debian_version)" = "4.0" ]; then
  /bin/sed -i -e 's/^\(dist[ ]*=[ ]*\)[^ ]*\([ ]*#.*\)$/\1etch\2/' /etc/xen-tools/xen-tools.conf
  /bin/sed -i -e 's/^\(dist[ ]*=[ ]*\)[^ ]*\([ ]*#.*\)$/\1lenny\2/' /etc/xen-tools/xen-tools.conf

Similarly, change the default swap size from 128Mo to 1Go (for safety reasons, even if most of the time it is not used):

/bin/sed -i -e 's/^\(swap[ ]*=[ ]*\)[^ ]*\([ ]*#.*\)$/\11Gb\2/' /etc/xen-tools/xen-tools.conf

Declare "debootstrap" as the default virtual computer OS installation method:

/bin/sed -i -e 's/^[# ]*\(debootstrap[ ]*=\).*$/\1 1/' /etc/xen-tools/xen-tools.conf

If Xen is configured to use the NAT mode, setup the default DomU network parameters for the creation of DomU with fixed IP:

if [ $(/bin/grep "^[^#]*nat" /etc/xen/xend-config.sxp | /usr/bin/wc --lines) -gt 0 ]; then
  /bin/sed -i -e 's/^[# ]*\(gateway[ ]*=\).*$/\1' \
            -e 's/^[# ]*\(netmask[ ]*=\).*$/\1' \

Note: If Xen is configured to use bridge mode, you can configure manually these settings by editing the /etc/xen-tools/xen-tools.conf file.

Using LVM volume group for virtual computer partitions

We will now configure Xen to use a LVM volume group. First, we detect the name of the first LVM volume group of the system :

LVM_VG=$(/sbin/vgdisplay \
  | /bin/grep "VG Name" \
  | /usr/bin/head --lines=1 \
  | /usr/bin/cut --characters=25-)

Note: If your server has more than one volume group, you can manually set the volume group to use :


Update the Xen tools configuration file:

/bin/sed -i -e "s/^# \(lvm = \).*/\1$LVM_VG/" /etc/xen-tools/xen-tools.conf

Once this done, we configure Xen Tools to use the right kernel wen creating virtual computers:

/bin/sed -i -e "s/^\(kernel =\).*\$/\1 \/boot\/vmlinuz-$(uname -r)/" \
            -e "s/^\(initrd =\).*\$/\1 \/boot\/initrd.img-$(uname -r)/" \

Configuring the Debian repository mirror

By default, the APT mirror used is located in United States of America. It is best to use a mirror closer from your location:


Note: If your server is hosted by OVH, you should use the following mirror:


Once the mirror choosed, update the Xen tools configuration:

CLEAN_APT_MIRROR=$(/bin/echo $APT_MIRROR | sed -e 's/\//\\\//g')
/bin/sed -i -e "s/^\(mirror = \).*/\1$CLEAN_APT_MIRROR/" /etc/xen-tools/xen-tools.conf

Creating a Xen Tools role for your virtual computers creation

In order to be able to correctly manage our guest operating systems (domU), we now create a Xen Tools role that will do the following on each virtual computer (domU) we are going to create:

  • Installing the following packages: locales, sudo, ntp, cron-apt, logwatch, rkhunter, chkrootkit, vim, screen, backup-manager and fail2ban
  • Creating the system user "xen-upgrade" with its rsa key for ssh authentication in order to ease upgrading guest operating systems (it is what we need sudo for).
  • Configure Backup Manager to backup the guest operating systems (domU), and copy the backups in the /var/archives folder of the host computer (dom0).

First, we download the configuration file of our new role named "automatic":

/usr/bin/wget \
/bin/chmod +x /etc/xen-tools/role.d/automatic

We create the "xen-backup" system user on the host computer (dom0):

/usr/sbin/adduser --system --shell /bin/sh --home /var/lib/xen-backup --disabled-password xen-backup

And we add it to the "backup" group:

/usr/sbin/adduser xen-backup backup

We create the RSA keys allowing the SSH authentication without password. In order to do this, create the folder that we will use to store this keys:

/bin/mkdir /etc/xen-tools/ssh-keys

And create the keys for the automatic authentication of the "xen-upgrade" (created by the "automatic" role on the guest OS (domU)) and "xen-backup" (that we created earlier on the dom0) accounts:

/usr/bin/ssh-keygen -t rsa -C "upgrade account key" -N "" -f /etc/xen-tools/ssh-keys/xen-upgrade-rsa
/usr/bin/ssh-keygen -t rsa -C "backup account key" -N "" -f /etc/xen-tools/ssh-keys/xen-backup-rsa

We setup the "xen-backup" user so that we can use the RSA key we just created to authenticated as it:

/bin/mkdir /var/lib/xen-backup/.ssh
/bin/cat /etc/xen-tools/ssh-keys/ \
    | /usr/bin/tee -a /var/lib/xen-backup/.ssh/authorized_keys
/bin/chown -R xen-backup:nogroup /var/lib/xen-backup/.ssh

We also install the script allowing us to upgrade the guest operating systems (domU) from the host computer (dom0):

/usr/bin/wget \
/bin/chmod +x /usr/bin/xen-apt-get

This script allow to upgrade all of the guest operating systems with this two commands:

xen-apt-get update
xen-apt-get upgrade

You can also upgrade a specific virtual computer (domU). You will learn more about its usage by reading the text displayed by:


Easing the access to guest operating systems (domU) shell (optionnal)

If you don't want to use password authentication for the root accounts of the guest operating systems, you can create a RSA key for authenticating as root on all guest operating systems. The "automatic" Xen Tools role will install it automaticaly if it find it. Please protect this RSA key with a strong password:

if [ ! -e ${HOME}/.ssh/id_rsa ]; then
  /usr/bin/ssh-keygen -t rsa -f ${HOME}/.ssh/id_rsa

Configuring virtual computers skeleton

We now create a skeleton with some default configurations (Exim 4, locales, timezone, bash and vim mainly) in order to reduce the configuration tasks needed by newly created virtual computers (domU).

First, we create the folder tree that will store the skeleton files (it is a standard linux organization: the skeleton is copied as is in the virtual operating system):

/bin/mkdir --parent /etc/xen-tools/skel/root
/bin/mkdir --parent /etc/xen-tools/skel/root/.ssh
/bin/mkdir --parent /etc/xen-tools/skel/etc/default
/bin/mkdir --parent /etc/xen-tools/skel/etc/exim4
/bin/mkdir --parent /etc/xen-tools/skel/etc/cron.d
/bin/mkdir --parent /etc/xen-tools/skel/etc/apt/apt.conf.d
/bin/mkdir --parent /etc/xen-tools/skel/etc/xen-data
/bin/mkdir --parent /etc/xen-tools/skel/usr/bin

We copy the configuration files of the host computer (dom0) into the skeleton, so that virtual operating systems has a very close configuration from our main host:

/bin/cp /root/.bashrc /etc/xen-tools/skel/root/
if [ -e /root/.vimrc ]; then
  /bin/cp /root/.vimrc /etc/xen-tools/skel/root/
/bin/cp /etc/timezone /etc/xen-tools/skel/etc/
/bin/cp /etc/localtime /etc/xen-tools/skel/etc/
/bin/cp /etc/locale.gen /etc/xen-tools/skel/etc/
/bin/cp /etc/environment /etc/xen-tools/skel/etc/
/bin/cp /etc/default/locale /etc/xen-tools/skel/etc/default/

Note: A part of this is only valid for Debian 4.0 Etch and 5.0 Lenny guest operating systems (but it work quite well on Ubuntu XD).

Add the Exim 4 configuration file in order for the root mails of guest operating systems (domU) to be processed by the SMTP server of the host computer (dom0) (we configured it earlier in this guide):

/usr/bin/wget \
/bin/sed -i -e "s/dc_smarthost=.*\$/dc_smarthost='${MAINDOM_IP}'/" \
echo "root@$(/bin/cat /etc/mailname)" > /etc/xen-tools/skel/root/.email

Add the SSH public key of the host computer (dom0) to the known hosts of the domU ssh client, in order for the backup to work correctly:

/usr/bin/ssh-keyscan -H -t rsa ${MAINDOM_IP} | /usr/bin/tee /etc/xen-tools/skel/root/.ssh/known_hosts


Also add the public RSA key of the Dom0 root account to the authorized keys for the domU root account:

if [ -e ${HOME}/.ssh/ ]; then
    /bin/cat ${HOME}/.ssh/ \
        | /usr/bin/tee -a /etc/xen-tools/skel/root/.ssh/authorized_keys


Configuring guest operating systems backups

The "automatic" Xen Tools role install the Backup Manager tool. Most of the guides available on this site will be updated with the needed informations to manage backups with this tool. We will here setup the backup of our virtual computers data:

First, we install into the virtual operating systems skeleton the update-bm-folders script introduced to you by my guide Install and configure Backup Manager on Debian 4.0 Etch.

/usr/bin/wget \
/bin/chmod +x /etc/xen-tools/skel/usr/bin/update-bm-folders

We download the default Backup Manager configuration for the guest operating systems:

/usr/bin/wget \
/bin/sed -i -e "s|[#]*\(.*BM_UPLOAD_SSH_HOSTS=\).*$|\1\"${MAINDOM_IP}\"|" \

And we add the "xen-backup" RSA private key of the host computer (dom0) to the guest operating systems (domU) skeleton:

/bin/cp /etc/xen-tools/ssh-keys/xen-backup-rsa /etc/xen-tools/skel/etc/xen-data/

Creating a Xen virtual computer

Base system installation

We now create our first Xen virtual computer. First we setup its hostname:


And we choose a IP address for the guest computer (change the last digit of the example IP):


Now, create the virtual computer by using the command lines bellow.

Important: Do not loose the password you enter here, it is the root password of your virtual computer.

  • For the default distribution (Debian 4.0 Etch or 5.0 Lenny):
    /usr/bin/xen-create-image --hostname $XEN_HOSTNAME \
        --ip $IP_ADDRESS --passwd --role automatic


    Note: To create a domU obtaining its IP address by DHCP (you may want this if your are using bridge networking), you can use this command:

    /usr/bin/xen-create-image --hostname $XEN_HOSTNAME \
        --dhcp --passwd --role automatic


  • For Ubuntu 8.04 Hardy Heron:
    /usr/bin/xen-create-image --hostname $XEN_HOSTNAME \
        --ip $IP_ADDRESS --passwd --role automatic \
        --dist=hardy --mirror=


    Note: To create a domU obtaining its IP address by DHCP (you may want this if your are using bridge networking), you can use this command:

    /usr/bin/xen-create-image --hostname $XEN_HOSTNAME \
        --dhcp --passwd --role automatic \
        --dist=hardy --mirror=


Note: The Ubuntu based DomU are sometimes having problems with the locales configuration. In order to correct this, you need to generate the locales that fit your language:

locale-gen fr_FR.UTF-8

and edit the file /etc/environment for it to contain "LANG=fr_FR.UTF-8". Once this two settings applied, restart the domU to take account of them (there is probably other methods, but this is the simplest way to do it i've been able to find).

Creating a /var partition for the domU

Once the virtual computer created, we add a partition for /var. Here, i choosed to create a 10 Giga Bytes partition:

LVM_VG=$(/bin/grep lvm /etc/xen-tools/xen-tools.conf | /bin/sed -e 's/lvm = //')
/sbin/lvcreate -n $XEN_HOSTNAME-var -L ${VAR_SIZE} $LVM_VG
/sbin/mkfs.ext3 /dev/$LVM_VG/$XEN_HOSTNAME-var

We update the new virtual computer configuration to use this partition:

if [ $(/bin/grep "disk[\t ]*=.*\]" /etc/xen/$XEN_HOSTNAME.cfg | /usr/bin/wc --lines) -eq 0 ]; then
  /bin/sed -i -e "/^disk[\t ]*=.*/a\\
    'phy:$LVM_VG\/$XEN_HOSTNAME-var,sda3,w'," \
  /bin/sed -i -e "s/^\(disk[\t ]*=.*\)\]/\1, 'phy:$LVM_VG\/$XEN_HOSTNAME-var,sda3,w' ]/" /etc/xen/$XEN_HOSTNAME.cfg

And we edit the fstab file of the virtual computer:

/bin/umount /dev/$LVM_VG/$XEN_HOSTNAME-disk
MOUNT_POINT=$(/bin/mktemp -d)
/bin/mount /dev/${LVM_VG}/${XEN_HOSTNAME}-disk ${MOUNT_POINT}
/bin/echo "/dev/sda3   /var    ext3    defaults                0       1" | /usr/bin/tee -a ${MOUNT_POINT}/etc/fstab
VAR_MOUNT_POINT=$(/bin/mktemp -d)
/bin/mount /dev/${LVM_VG}/${XEN_HOSTNAME}-var ${VAR_MOUNT_POINT}
/bin/cp -a ${MOUNT_POINT}/var/* ${VAR_MOUNT_POINT}
/bin/umount ${VAR_MOUNT_POINT}
/bin/umount ${MOUNT_POINT}

Starting the virtual computer (domU)

We can now start our new virtual computer (domU):

/usr/sbin/xm create /etc/xen/$XEN_HOSTNAME.cfg

You can fetch the list of running virtual computers with the command:

/usr/sbin/xm list

We now use SSH to connect to our virtual computer:

/usr/bin/ssh root@$XEN_HOSTNAME

Note: If you have created a RSA key for root authentication, you'll be ask for the RSA key password, not for the Xen DomU root password.

"Hardware" access to the virtual computer

If you encounter problems to connect by SSH to your virtual computer, you can access to the "console (ttY)" of your newly created domaine with:

/usr/sbin/xm console $XEN_HOSTNAME

Warning: The Xen console act as a serial console. This can be a problem if you use Vim.

To exit this virtual console, use the shortcut : <Ctrl> <]>

Automatic startup of virtual computers

If you want some of your virtual computers to start automaticaly at your main system startup (this is needed for servers), you need to create a "auto" folder:

/bin/mkdir /etc/xen/auto

Once this done, place the configuration of virtual computers that need to be automaticaly started into this folder. For exemple, to start automaticaly the "apache2" virtual computer, use this command:

/bin/mv /etc/xen/apache2.cfg /etc/xen/auto/



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