Debian Squeeze XEN basic setup

Install Xen:

#> aptitude install xen-hypervisor-4.0-amd64 linux-image-xen-amd64 xen-tools

Sqeeuze use Grub 2 - the defaults are wrong for Xen.
Xen hypervisor should be the first entry, so you should do this:

#> mv /etc/grub.d/10_linux /etc/grub.d/100_linux

After that disable the OS prober, so that you don’t have entries for virtual machines installed on a LVM partition.

#> echo "GRUB_DISABLE_OS_PROBER=true" >> /etc/default/grub
#> update-grub2

Xen tries to save-state the VM’s when doing Dom0 shutdown.
This save/restore has never been successful for me, so I disable it in /etc/default/xendomains to make sure machines gets shut down too:

XENDOMAINS_RESTORE=false
XENDOMAINS_SAVE=""

Enable the network bridge in /etc/xen/xend-config.sxp (uncomment existing line).
I also set some other useful params (for me):

(network-script network-bridge)
(dom0-min-mem 128)
(dom0-cpus 1)
(vnc-listen '127.0.0.1')
(vncpasswd '')


Add independent wallclocl in sysctl dom0

#> echo xen.independent_wallclock=1 >> /etc/sysctl.conf

and also in the domUs. Setup ntpdate update at 1hour for example in domUs.
This will save you a lot of clocksync headachecs.

Config /etc/xen-tools/xen-tools.conf contains default values the xen-create-image script will use. Most important are:

# Virtual machine disks are created as logical volumes in volume group universe (LVM storage is much faster than file)
lvm = vg001

install-method = debootstrap

size = 20Gb # Disk image size.
memory = 256Mb # Memory size
swap = 4Gb # Swap size
fs = ext3 # use the EXT3 filesystem for the disk image.
dist = `xt-guess-suite-and-mirror --suite` # Default distribution to install.

gateway = 1.2.3.4
netmask = 255.255.255.0

# When creating an image, interactively setup root password
passwd = 1

# I think this option was this per default, but it doesn't hurt to mention.
mirror = `xt-guess-suite-and-mirror --mirror`

mirror_squeeze = http://ftp.bg.debian.org/debian/

# let xen-create-image use pygrub, so that the grub from the VM is used, which means you no longer need to store kernels outside the VM's. Keeps this very flexible.
pygrub=1

scsi=1

Script to create vms (copied from http://blog.bigsmoke.us/):

#!/bin/bash

dist=$1
hostname=$2
ip=$3

if [ -z "$hostname" -o -z "$ip" -o -z "$dist" ]; then
echo "No dist, hostname or ip specified"
echo "Usage: $0 dist hostname ip"
exit 1
fi

# --scsi is specified because when creating maverick for instance, the xvda disk that is used can't be accessed.
# The --scsi flag causes names like sda to be used.
xen-create-image --hostname $hostname --ip $ip --vcpus 2 --pygrub --dist $dist


Usage of the script should be simple. When creating a VM named ‘host’, start it and attach console:

xm create -c /etc/xen/host.cfg

You can go back to Dom0 console with ctrl-].
Place a symlink in /etc/xen/auto to start the VM on boot.

As a sidenote: when creating a lenny, the script installs a xen kernel in the VM.
When installing maverick, it installs a normal kernel.
Normals kernels since version 2.6.32 (I believe) support pv_ops, meaning they can run on hypervisors like Xen’s.

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