Install Xen

Well xend configuration is pretty easy to do. I remember having hard time with it, but by moving network part to network configuration seems to make it much more simpler. Here's my configuration :

# We want migration
(xend-relocation-server yes)
# We want it on port 8002
(xend-relocation-port 8002)
# We want to listen on the whole network, but don't specify an IP if you use OCFS2 shared configuration as shown below
(xend-relocation-address '')

# We don't do any change on our network configuration when Xen start
(network-script network-dummy)

# We use bridging
(vif-script vif-bridge)

# I want at least 196Mo for my dom0. You to tune this value.
(dom0-min-mem 196)
# I give all my CPU to dom0 (default)
(dom0-cpu 0)

I choose to setup the bridge in the network configuration instead of using xen scripts. Xen scripts don't work well with channel bonding. This in /etc/network/interfaces will first setup channel bonding then it'll add bridging

auto br0
iface br0 inet static
        address 192.168.10.9
        netmask 255.255.255.0
        broadcast 192.168.10.255
        network 192.168.10.0
        gateway 192.168.10.1
        dns-nameservers 192.168.10.5
        dns-search irovision.ch 
        pre-up ip link set eth0 up
        pre-up ip link set eth1 up
        pre-up modprobe bond0
        pre-up ip link set bond0 up 
        pre-up ifenslave bond0 eth0 eth1
        pre-up modprobe bridge
        pre-up brctl addbr br0 
        pre-up brctl addif br0 bond0
        pre-up brctl stp br0 off
        pre-up brctl setfd br0 0

actually if you ifdown br0 then ifup br0 it'll fail because the network configuration doesn't disable the bridge and un-enslave network card from the bond. I'll do it …

To make bonding works, you need to create a file in /etc/modprobe.d/ in order to define how your bonding driver will be loaded by the kernel. I called this file bonding :

# For channel bonding
# File /etc/modprobe.d/bonding
alias bond0 bonding
options bond0 mode=1 miimon=100 downdelay=200 updelay=200

Ok this works very well. You just need to correct some little details. First of all, I use xen-tools which works very, very well. It allows to create new virtual server in less than a second when correctly configured. Like xen-create-image –hostname=vserver18 –ip=10.0.0.18 and you've got a Debian Etch ready to run and to migrate around …

First I've installed the vserver linux image from Debian : sudo aptitude install linux-image-2.6.18-6-xen-vserver-686. This provide kernel for virtual server running on the top of Xen.

I've a OCFS2 volume mounted on /srv/os_img_pool. This is where my Xend configuration and my virtual server image reside. So in /etc/xen-tools/xen-tools.conf, I've set dir = /srv/os_img_pool/. So here is my xen-tools.conf :

# Where all my xen image reside
dir = /srv/os_img_pool
# I use debootstrap to generate a new vserver
deboostrap = 1
# My default value for disk size, memory and swap 
size = 5Gb
memory = 256Mb
swap = 256Mb
# I want ext3, use etch distrib and use spare disk images
fs = ext3
dist = etch
image = sparse
# I set default value for my network
gateway = 10.0.0.254
netmask = 255.255.255.0
# Path to Debian virtual server linux image
kernel = /boot/vmlinuz-2.6.18-6-xen-vserver-686
initrd = /boot/initrd.img-2.6.18-6-xen-vserver-68
# My debian mirror (from switzerland)
mirror = http://ftp.ch.debian.org/debian/

Then I created /srv/os_img_pool/conf and I copied in it /etc/xen : cp -a /etc/xen/ /srv/os_img_pool/conf/. I did this to share the same xend configuration between all my dom0. You only need to create a symbolic link :

X00:~# mv /etc/xen /etc/xen.bck
X00:~# ln -s /srv/os_img_pool/conf/xen /etc/xen

What is very important here, is that you do this on all your dom0. You can use clusterssh to command all your dom0 at once. But if you've 4 dom0 (X00 to X03), both command should be done on X00 to X03 with the OCFS2 volume mounted.

I didn't put the xen-tools configuration on the OCFS2 volume … Why ? Did thing of that while writing this document, so I will do it later, but by applying the same process you would have the same xen-tools configuration on every dom0 (instead of copying it by hand like I did).

Now that you've the same configuration for xen-tools and xend on every dom0, you can issue the xen-create-image command and start a new virtual server, migrate, …

That's true. It works in Lenny, but actually it's not sure that Lenny could run as dom0. So I've made a little the script that would do the job.

 
#! /bin/sh
### BEGIN INIT INFO
# Provides:          mountocfs2
# Required-Start:    o2cb $local_fs
# Required-Stop:
# Should-Start:      $network
# Default-Start:     S
# Default-Stop:
# Short-Description: Wait for o2cb service to mount ocfs2 
# Description:       OCFS2 Filesystem are not correctly handled by
#                    mountnfs.sh, this script should correct that.
### END INIT INFO
 
PATH=/sbin:/bin
. /lib/init/vars.sh
 
. /lib/lsb/init-functions
. /lib/init/mount-functions.sh
 
do_start() {
        [ -f /etc/fstab ]  return
        exec 9<&0 </etc/fstab
 
        OCFS2=no
        while read DEV MTPT FSTYPE OPTS REST
        do
                case "$DEV" in
                  ""\#*)
                        continue
                        
                esac
                case "$OPTS" in
                  noauto*,noautonoauto,**,noauto,*)
                        continue
                        
                esac
                case "$FSTYPE" in
                  ocfs2)
                        OCFS2=yes
                  
                esac
        done
 
        exec 0<&9 9<&-
 
        if [ "$OCFS2" = yes ]
        then
                log_action_begin_msg "Mounting all OCFS2 filesystem"
                mount -a -t ocfs2
                log_action_end_msg $?
        fi
}
 
case "$1" in
  start"")
        do_start
        
  restartreloadforce-reload)
        echo "Error: argument '$1' not supported" >&2
        exit 3
        
  stop)
        # Nop
        
  *)
        echo "Usage: mountocfs2.sh [startstop]" >&2
        exit 3
        
esac
:

The script ...

Put this script in /etc/init.d/ and then add to your start up sequence (the S level and after 60, because o2cb starts at 60) with the command update-rc.d :

$ sudo update-rc.d mountocfs2.sh start 61 S .

Then you're system is really ready to work.

• Read my page about OCFS2.