The Perfect Xen Setup For Debian And Ubuntu - Page 4

4 Create A Virtual Machine (domU)

Next we create an image of a virtual machine. It will be a basic Debian system. This image will be the template for all our virtual machines. Whenever we want to create a new virtual machine, we just copy this image, create a new Xen configuration file and boot the copy, and then we can go on and configure the copy to our needs (e.g install a mail server, web server, DNS server, etc. on it). All our images will be on the /vserver partition which should be the largest one we have.

mkdir /vserver/vm_base
mkdir /vserver/images

Now we create a 1 GB image file and a 500 MB swap image. In the end the virtual machines will have 1 GB space and 500 MB swap. These are just example values, in the real world you might want to have more space for your virtual machines (e.g. between 5 and 30 GB), so just increase the value of count to create larger images.

dd if=/dev/zero of=/vserver/images/vm_base.img bs=1024k count=1000
dd if=/dev/zero of=/vserver/images/vm_base-swap.img bs=1024k count=500

Then we format /vserver/images/vm_base.img with ext3 and vm_base-swap.img with swap:

mkfs.ext3 /vserver/images/vm_base.img

When you see the following, answer with y:

/vserver/images/mail.img is not a block special device.
Proceed anyway? (y,n) <-- y

mkswap /vserver/images/vm_base-swap.img

4.1 Install A Basic Debian In The Image

In order to install a basic Debian system in our image, we mount the image, run debootstrap and a few other commands:

mount -o loop /vserver/images/vm_base.img /vserver/vm_base
debootstrap --arch i386 sarge /vserver/vm_base/ http://ftp2.de.debian.org/debian

chroot /vserver/vm_base
apt-setup

You are asked the following question:

Archive access method for apt: <-- http

Then select a mirror close to you.

Afterwards, edit /etc/apt/sources.list and replace testing with stable. That's how my /etc/apt/sources.list looks: 

deb http://ftp2.de.debian.org/debian/ stable main
deb-src http://ftp2.de.debian.org/debian/ stable main

deb http://security.debian.org/ stable/updates main

Then run

apt-get update

Now we set up our locales. If we do not do this now, we will see some ugly warnings during base-config like these:

perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
        LANGUAGE = "en_DE:en_US:en_GB:en",
        LC_ALL = (unset),
        LANG = "en_US"
    are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
locale: Cannot set LC_CTYPE to default locale: No such file or directory
locale: Cannot set LC_MESSAGES to default locale: No such file or directory
locale: Cannot set LC_ALL to default locale: No such file or directory

They are not serious, but ugly... So we run

apt-get install localeconf

Select locales to install (e.g. en_US ISO-8859-1) and select the standard locale (e.g. en_US).

You will be asked a few questions:

Manage locale configuration files with debconf? <-- Yes
Environment settings that should override the default locale: <-- do not select anything
Replace existing locale configuration files? <-- Yes
Default system locale: <-- e.g. en_US ISO-8859-1

Next run

base-config

You will see a menu with installation options. This is what we do:

  1. Configure timezone
  2. Set up users and passwords
  3. Select and install packages (when it comes to Choose software to install:, you can choose whatever you like; I, however, choose nothing because I want to install a basic system.)
  4. Finish configuring the base system

Don't deal with the other menu items, you don't need them. Then we remove nfs-common and delete /etc/hostname:

apt-get remove nfs-common
rm -f /etc/hostname

Then edit /etc/fstab. It should look like this:

/dev/hda1               /               ext3    defaults        1       2
/dev/hda2               none            swap    sw            0       0
/dev/pts                devpts          gid=5,mode=620    0       0
none                    /dev/shm        tmpfs   defaults     0       0

Change /etc/network/interfaces to look like this:

auto lo
iface lo inet loopback
        address 127.0.0.1
        netmask 255.0.0.0

Then create /etc/hosts:

127.0.0.1       localhost.localdomain   localhost

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts

Now we leave the chroot environment:

exit

Then we copy over the kernel modules to our virtual machine image and unmount the image:

cp -dpR /lib/modules/2.6.11.12-xenU /vserver/vm_base/lib/modules/
mv /vserver/vm_base/lib/tls /vserver/vm_base/lib/tls.disabled
umount /vserver/vm_base

If you get a warning like this: umount: /vserver/vm_base: device is busy don't worry about it, it's not important.

Now our virtual machine image template is ready!

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