[Xen-users] How to install Xen 3.0 on Slackware 10.2

[Richard Hamel-Smith <richardhamelsmith@xxxxxxxxx>]

Last weekend, when I was struggling to understand how to get Xen to work, I would have loved to have found a document detailling the steps. So, for anybody who might be struggling with the same problem, here's my HOWTO. It may not accurate, but it worked for me.

How to install Xen 3.0

Download the tarball from the Xen site

wget http://www.cl.cam.ac.uk/Research/SRG/netos/xen/downloads/xen-3.0.0-src.tgz

make a directory somewhere and untar the tarball into it. You will get a directory called xen-unstable.

change directory into xen-unstable

run make world

this will download a kernel from www.kernel.org and compile everything you need. get a coffee or take a nap. The kernel took 3.5 hours to download at home over dialup.

When it's finished, run make install

This installs the new kernels (there are two) into /boot. Don't worry... it doesn't overwrite the old one.

Installing GRUB

You need to install GRUB, if it isn't already on your machine. You have to use CVS for this, as follows :-

# cvs -z3 -d:pserver:anonymous@xxxxxxxxxxxxxx:/sources/grub co grub

This eventually downloads everything into a directory called grub.

Change directory to grub and run

# ./configure && make && make install

This puts GRUB into /usr/local/*sbin*.

Then, as root, run :-

# grub-install

It may give an error. Just do it again.

You need to make a menu entry into /boot/grub/menu.lst to boot Xen. I used :-

title Xen
root (hd0,4)
kernel /boot/xen.gz dom0_mem=262144
module /boot/vmlinuz-2.6.12-xen0 root=/dev/hda5 ro

Then, reboot into your new Xen setup. You should be running a kernel
which ends in -xen0. Check with 'uname -a'.

Setting up a guest domain

The next thing is to setup the domain you will run as a guest under your master domain. I installed Zenwalk 2.01 on /dev/hda3 and made sure it was working properly first, before attempting to use it as a guest.

To set up a guest domain, there are a series of steps.

Create a config file. I used /etc/xen/mydom, which contains :-

kernel = "/boot/vmlinuz-2.6.12.6-xenU"
memory = 128
name = "zenwalk"
vif = [ 'mac=aa:00:00:00:00:11']
disk = [ 'phy:hda3,hda3,w' ]
dhcp = "dhcp"
root = "/dev/hda3 ro"
extra = "4"

This means :-

boot off the kernel in /boot/vmlinuz-2.6.12.6-zenU
assign 128MB of RAM to this guest
assign hostname = "zenwalk" ? I think, perhaps it is domain-name
assign a mac address of aa:00:00:00:00:11 to the virtual interface eth0 in the domain
map the partition /dev/hda3 to the virtual machine as /dev/hda3 and allow writing to it
use DHCP in the virtual machine (you still have to set up DHCP inside the virtual machine anyhow - PITA)
use /dev/hda3 as the root partition
boot to runlevel 4 in the virtual machine

The next thing to do, is to mount the partition where I installed Zenwalk on /mnt/hd. Then,

mount /dev/hda3 /mnt/hd
cd /mnt/hd/lib/modules
cp -av /lib/modules/2.6.12.6-xenU/* .
cd /mnt/hd/lib
mv tls tls.disabled

Installing VNC

Then, download and untar the latest free version of VNC from http://www.realvnc.com/. You can't install it just yet, you need to be inside the virtual machine to install it.

Once you DO have VNC installed, you need to edit /mnt/hd/etc/X11/gdm/gdm.conf to get GDM to start up Xvnc automatically when the VM boots. Add a stanza for VNC as follows :-

[server-VNC]
name=VNC server
command=/usr/bin/Xvnc -SecurityTypes None -geometry 800x600 -depth 24
flexible=true

Change the stanza [servers] to :-

[servers]
0=VNC

Fiddling with the scripts

Ok, now because this is Slackware and not Debian and not RedHat? or Fedora or Centos, you need to "fiddle" with some of the scripts they give you.

To begin with, I couldn't get the default setup to work at all. I needed to edit /etc/xen/xend-config.sxp to use the NAT setup instead of the bridge setup. To do this, you need to comment the lines

(network-script network-bridge)
(vif-script vif-bridge)

and un-comment the lines

(network-script network-nat)
(vif-script vif-nat)

In /etc/xen/scripts/network-nat and vif-nat, change dhcp=${dhcp:-no} to dhcp=${dhcp:-yes}.

Also, in the function dhcp_start(), I added

/usr/sbin/dhcpd

just before the line

"$dhcpd_init_file" restart

This was the only way I could get it to start DHCPD automatically.

To get Zenwalk to use DHCP, edit /mnt/hd/etc/rc.d/rc.inet1.conf and change the line '*USE_DHCP[0]="no"*' to '*USE_DHCP[0]="yes"*'.

I also had to edit /etc/xen/scripts/xen-network-common.sh because it didn't work with Slackware. This was critical so I'm including the whole script.

#
# Copyright (c) 2005 XenSource Ltd.
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of version 2.1 of the GNU Lesser General Public
# License as published by the Free Software Foundation.
#
# This library 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
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#


# On SuSE it is necessary to run a command before transfering addresses and
# routes from the physical interface to the virtual.  This command creates a
# variable $HWD_CONFIG_0 that specifies the appropriate configuration for
# ifup.

# Gentoo doesn't have ifup/ifdown, so we define appropriate alternatives.

# Other platforms just use ifup / ifdown directly.

##
# preiftransfer
#
# @param $1 The current name for the physical device, which is also the name
#           that the virtual device will take once the physical device has
#           been renamed.

if [ -e /etc/SuSE-release ]
then
  preiftransfer()
  {
    eval `/sbin/getcfg -d /etc/sysconfig/network/ -f ifcfg- -- $1`
  }
  ifup()
  {
    /sbin/ifup ${HWD_CONFIG_0} $1
  }
elif ! which ifup >&/dev/null
then
  if [ -e /etc/conf.d/net ]
  then
    preiftransfer()
    {
      true
    }
    ifup()
    {
      /etc/init.d/net.$1 start
    }
    ifdown()
    {
      /etc/init.d/net.$1 stop
    }
  else

if [ -e /etc/slackware-version ]
then
    preiftransfer()
    {
      true
    }
    ifup()
    {
      true
    }
    ifdown()
    {
      true
    }
else

    logger -p "daemon.crit" -- \
      "You don't have ifup and don't seem to be running Gentoo either!"
    exit 1
fi
  fi
else
  preiftransfer()
  {
    true
  }
fi


first_file()
{
  t="$1"
  shift
  for file in $@
  do
    if [ "$t" "$file" ]
    then
      echo "$file"
      return
    fi
  done
}

find_dhcpd_conf_file()
{
  first_file -f /etc/dhcp3/dhcpd.conf /etc/dhcpd.conf
}


find_dhcpd_init_file()
{
  first_file -x /etc/init.d/{dhcp3-server,dhcp,dhcpd}
}

I think that was all the fiddling I had to do. Mind you, it took me a good week to get this to work. I'm just slow, I guess.

Extra scripts I wrote

I wrote a script to help me manage the domain.
#!/bin/sh
#
# xmctl
#
# Richard Hamel-Smith - Mon Jan 16 16:40:07 AST 2006
#===================================================
pause() {
   echo -e "press  to continue \c"
   read dummy
}
while :
do
   clear
   brctl show
   xm list
   echo -e "
   XM Menu
   =======
   1. create mydom
   2. destroy mydom
   3. connect to mydom
   4. most /var/log/messages

   5. most /var/log/debug
   6. most /var/log/syslog
   q. quit 

   opt : \c"
   read OPT
   case $OPT in
      1) 
         killall dhcpd 
         xm create mydom -c 
      ;;
      2) xm destroy zenwalk ;;
      3) xm unpause zenwalk ; xm console zenwalk ;;
      4) most /var/log/messages ;;
      5) most /var/log/debug ;;
      6) most /var/log/syslog ;;
      *) exit ;;
   esac
done
#===================================================

I wrote another script to launch vncviewer with the correct IP address, which keeps changing each time you create a new domain.

#!/bin/sh
#
# vnc - calls vncviewer with the correct IP address
#
# Richard Hamel-Smith - Fri Jan 20 10:34:39 AST 2006
#===================================================
addr="`
tail -1 /etc/dhcpd.conf |\
awk -F';' '{ print $2 }' |\
awk '{ print $2 }'`"
echo $addr
vncviewer $addr
#===================================================

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