Creating JeOS virtual machines in Ubuntu

The two tools I use for creating new vm’s with libvirt are virt-install and vmbuilder. I use virt-install when I will be installing an OS from installable media or using an existing disk image, and vmbuilder when I need to create JeOS based vm’s.

After following the guides at wiki.ubuntu.com I ended up with two fairly long template commands:

sudo virt-install --hvm -n <hostname> -r <memory> -f <hdd_image> -s <image_size_in_gb> 
-c <iso> --accelerate --connect=qemu:///system --vnc --noautoconsole

sudo vmbuilder kvm ubuntu --suite intrepid --flavour virtual --arch amd64 -o --libvirt qemu:///system 
--part vmbuilder.partition --user myname --name 'My Name' --pass default --addpkg puppet 
--addpkg unattended-upgrades --addpkg acpid --mirror http://apt/ubuntu --tmpfs - 
--firstboot vmbuilder.firstboot.sh --hostname <hostname> --mem <memory> --dest <hdd_image_basedir>

The command for virt-install is pretty lean compared to the command for vmbuilder. But vmbuilder allows for most of the configuration to be stored in ~/.vmbuilder.cfg. It did take a bit of digging as not a lot about it was on the ubuntu wiki though.

If you are looking for extra help in vmbuilder have a look at:

vmbuilder kvm ubuntu --help

And after setting up the config files below, to create new machines I just use for example:

sudo vmbuilder kvm ubuntu --hostname cacti --mem 256 --dest /srv/libvirt/cacti/

So here is the config I use as an example for anybody who plans on using vmbuilder a lot.

~/.vmbuilder.cfg

[DEFAULT]
arch = amd64
part = vmbuilder.partition
user = myname
name = My Name
pass = default
tmpfs = -
firstboot = vmbuilder.firstboot.sh
firstlogin = vmbuilder.firstlogin.sh

[ubuntu]
mirror = http://apt/ubuntu
suite = intrepid
flavour = virtual
addpkg = puppet, unattended-upgrades, acpid
part = vmbuilder.partition
#ssh_user_key = .ssh/authorized_keys

[kvm]
libvirt = qemu:///system

http://apt/ubuntu is my local approx machine for caching packages. The ssh_user_key is commented out at the moment as it creates the file correctly in the user account, but sets the owner to root.

vmbuilder.partition

root 8000
swap 4000

vmbuilder.firstboot.sh

# This script will run the first time the virtual machine boots
# It is ran as root.

locale-gen en_AU.UTF-8

apt-get update
apt-get install -qqy --force-yes openssh-server

The firstboot script just ensures that if I create an image and duplicate it a few times that each machine will have a unique ssh host key. But the image must be duplicated before the first boot.

vmbuilder.firstlogin.sh

# This script will run the first time the virtual machine boots
# It is ran as root.

# Prompt for a password change
passwd

Because I did not want to put my password in the configuration files as plain text, I only put default as the password and when I login for the first time I am prompted to change it. This will hopefully be fixed when I get the ssh_user_key working though.

VMBuilder/plugins/libvirt/templates/libvirtxml.tmpl

<domain type='kvm'>
  <name>$hostname</name>
  <memory>#echo $mem * 1024 #</memory>
  <vcpu>1</vcpu>
  <os>
    <type>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
  </features>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <devices>
    <emulator>/usr/bin/kvm</emulator>
    <interface type='bridge'>
      <source bridge='br0'/>
      <model type='virtio'/>
    </interface>
    <input type='mouse' bus='ps2'/>
    <graphics type='vnc' port='-1' listen='127.0.0.1'/>
#for $disk in $disks
    <disk type='file' device='disk'>
      <source file='$disk.filename' />
      <target dev='hd$disk.devletters()' />
    </disk>
#end for
  </devices>
</domain>

And the only difference with this template and the default one is this template file sets up bridge networking with virtio by default.