3 Creating Virtual Machines (domU)

Now let's create our first guest domain, xen1.example.com, running Gutsy Gibbon (gutsy) with the IP address 192.168.0.101:

xen-create-image --hostname=xen1.example.com --size=2Gb --swap=256Mb --ide \
--ip=192.168.0.101 --netmask=255.255.255.0 --gateway=192.168.0.1 --force \
--dir=/home/xen --memory=64Mb --arch=i386 --kernel=/boot/vmlinuz-2.6.22-14-xen \
--initrd=/boot/initrd.img-2.6.22-14-xen --debootstrap --dist=gutsy \
--mirror=http://de.archive.ubuntu.com/ubuntu/ --passwd

A lot of switches are unnecessary here because we specified the same details in /etc/xen-tools/xen-tools.conf but it shows that you can specify the desired settings either on the command line or in /etc/xen-tools/xen-tools.conf. Please make sure that you specify --ide, otherwise your virtual machine might not boot!

(To learn more about the available options, take a look at the xen-create-image man page:

man xen-create-image

)

The xen-create-image command will now create the xen1.example.com virtual machine for us. This can take a few minutes. The output should be similar to this one:

root@server1:~# xen-create-image --hostname=xen1.example.com --size=2Gb --swap=256Mb --ide \
--dir=/home/xen --memory=64Mb --arch=i386 --kernel=/boot/vmlinuz-2.6.22-14-xen \
--initrd=/boot/initrd.img-2.6.22-14-xen --debootstrap --dist=gutsy \
--mirror=http://de.archive.ubuntu.com/ubuntu/ --passwd> --ip=192.168.0.101 --netmask=255.255.255.0 --gateway=192.168.0.1 --force \
> --dir=/home/xen --memory=64Mb --arch=i386 --kernel=/boot/vmlinuz-2.6.22-14-xen \
> --initrd=/boot/initrd.img-2.6.22-14-xen --debootstrap --dist=gutsy \
> --mirror=http://de.archive.ubuntu.com/ubuntu/ --passwd
Unknown option: debootstrap

General Information
--------------------
Hostname       :  xen1.example.com
Distribution   :  gutsy
Fileystem Type :  ext3

Size Information
----------------
Image size     :  2Gb
Swap size      :  256Mb
Image type     :  sparse
Memory size    :  64Mb
Kernel path    :  /boot/vmlinuz-2.6.22-14-xen
Initrd path    :  /boot/initrd.img-2.6.22-14-xen

Networking Information
----------------------
IP Address 1   : 192.168.0.101
Netmask        : 255.255.255.0
Broadcast      : 192.168.0.255
Gateway        : 192.168.0.1


Creating swap image: /home/xen/domains/xen1.example.com/swap.img
Done

Creating disk image: /home/xen/domains/xen1.example.com/disk.img
Done

Creating ext3 filesystem on /home/xen/domains/xen1.example.com/disk.img
Done
Installation method: debootstrap
Done

Running hooks
Done

No role script specified.  Skipping

Creating Xen configuration file
Done
Setting up root password
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
All done


Logfile produced at:
         /var/log/xen-tools/xen1.example.com.log
root@server1:~#

There should now be a xen1.example.com configuration file - /etc/xen/xen1.example.com.cfg. Take a look at it to become familiar with virtual machine configuration files:

cat /etc/xen/xen1.example.com.cfg

#
# Configuration file for the Xen instance xen1.example.com, created
# by xen-tools 3.5 on Tue Oct 30 14:55:46 2007.
#
#
#  Kernel + memory size
#
kernel      = '/boot/vmlinuz-2.6.22-14-xen'
ramdisk     = '/boot/initrd.img-2.6.22-14-xen'
memory      = '64'
#
#  Disk device(s).
#
root        = '/dev/hda1 ro'
disk        = [ 'file:/home/xen/domains/xen1.example.com/disk.img,hda1,w', 'file:/home/xen/domains/xen1.example.com/swap.img,hda2,w' ]
#
#  Hostname
#
name        = 'xen1.example.com'
#
#  Networking
#
vif         = [ 'ip=192.168.0.101' ]
#
#  Behaviour
#
on_poweroff = 'destroy'
on_reboot   = 'restart'
on_crash    = 'restart'

(Please note: if you have a dual-core CPU and want the virtual machine to use both CPU cores, please add the line vcpus = '2' to the configuration file, like this:

vi /etc/xen/xen1.example.com.cfg

#
# Configuration file for the Xen instance xen1.example.com, created
# by xen-tools 3.5 on Tue Oct 30 14:55:46 2007.
#
#
#  Kernel + memory size
#
kernel      = '/boot/vmlinuz-2.6.22-14-xen'
ramdisk     = '/boot/initrd.img-2.6.22-14-xen'
memory      = '64'
vcpus       = '2'
#
#  Disk device(s).
#
root        = '/dev/hda1 ro'
disk        = [ 'file:/home/xen/domains/xen1.example.com/disk.img,hda1,w', 'file:/home/xen/domains/xen1.example.com/swap.img,hda2,w' ]
#
#  Hostname
#
name        = 'xen1.example.com'
#
#  Networking
#
vif         = [ 'ip=192.168.0.101' ]
#
#  Behaviour
#
on_poweroff = 'destroy'
on_reboot   = 'restart'
on_crash    = 'restart'

Afterwards, in the virtual machine, you can run the command

cat /proc/cpuinfo

to check that both CPU cores are being used by the virtual machine. The output could look like this if your vm is using both cores:

xen1:~# cat /proc/cpuinfo
processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 75
model name      : AMD Athlon(tm) 64 X2 Dual Core Processor 4200+
stepping        : 2
cpu MHz         : 2210.054
cache size      : 512 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu tsc msr pae mce cx8 apic mca cmov pat pse36 clflush mmx fxsr 
sse sse2 ht syscall nx mmxext fxsr_opt lm 3dnowext 3dnow pni 
cx16 lahf_lm cmp_legacy svm cr8legacy ts fid vid ttp tm stc
bogomips        : 5526.81

processor       : 1
vendor_id       : AuthenticAMD
cpu family      : 15
model           : 75
model name      : AMD Athlon(tm) 64 X2 Dual Core Processor 4200+
stepping        : 2
cpu MHz         : 2210.054
cache size      : 512 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 1
wp              : yes
flags           : fpu tsc msr pae mce cx8 apic mca cmov pat pse36 clflush mmx fxsr 
sse sse2 ht syscall nx mmxext fxsr_opt lm 3dnowext 3dnow up pni 
cx16 lahf_lm cmp_legacy svm cr8legacy ts fid vid ttp tm stc
bogomips        : 5526.81

xen1:~#

)

To start the virtual machine, run

xm create /etc/xen/xen1.example.com.cfg

Run

xm console xen1.example.com

to log in on that virtual machine (type CTRL+] if you are at the console, or CTRL+5 if you're using PuTTY to go back to dom0), or use an SSH client to connect to it (192.168.0.101).

To get a list of running virtual machines, type

xm list

The output should look like this:

root@server1:~# xm list
Name                                      ID Mem(MiB) VCPUs State   Time(s)
Domain-0                                   0      327     1 r-----    687.7
xen1.example.com                           1       64     1 -b----     22.4
root@server1:~#

To shut down xen1.example.com, do this:

xm shutdown xen1.example.com

If you want vm01 to start automatically at the next boot of the system, then do this:

ln -s /etc/xen/xen1.example.com.cfg /etc/xen/auto

Here are the most important Xen commands:

xm create -c /path/to/config - Start a virtual machine.
xm shutdown <name> - Stop a virtual machine.
xm destroy <name> - Stop a virtual machine immediately without shutting it down. It's as if you switch off the power button.
xm list - List all running systems.
xm console <name> - Log in on a virtual machine.
xm help - List of all commands.

Let's create a second vm, xen2.example.com with the IP address 192.168.0.102 and Feisty Fawn (feisty) as the operating system:

xen-create-image --hostname=xen2.example.com --size=2Gb --swap=256Mb --ide \
--ip=192.168.0.102 --netmask=255.255.255.0 --gateway=192.168.0.1 --force \
--dir=/home/xen --memory=64Mb --arch=i386 --kernel=/boot/vmlinuz-2.6.22-14-xen \
--initrd=/boot/initrd.img-2.6.22-14-xen --debootstrap --dist=feisty \
--mirror=http://de.archive.ubuntu.com/ubuntu/ --passwd

Afterwards, you can start xen2.example.com like this:

xm create /etc/xen/xen2.example.com.cfg

... and shut it down like this:

xm shutdown xen2.example.com

A list of all virtual machines that were created with the xen-create-image command is available under

xen-list-images

root@server1:~# xen-list-images
Name: xen1.example.com
Memory: 64
IP: 192.168.0.101

Name: xen2.example.com
Memory: 64
IP: 192.168.0.102
root@server1:~#

To learn more about what you can do with xen-tools, take a look at this tutorial: http://www.howtoforge.com/xen_tools_xen_shell_argo

4 Links

• Xen: http://www.xensource.com/xen/
• xen-tools: http://xen-tools.org/software/xen-tools
• Ubuntu: http://www.ubuntu.com/