Example: Ubuntu image

In this example, we'll use the network installation ISO, since it's a smaller image. The 64-bit 12.04 network installer ISO is at http://archive.ubuntu.com/ubuntu/dists/precise/main/installer-amd64/current/images/netboot/mini.iso

Start the installation process using either virt-manager or virt-install as described in the previous section. If using virt-install, don't forget to connect your VNC client to the virtual machine.

We will assume the name of your virtual machine image is ubuntu-12.04, which we need to know when using virsh commands to manipulate the state of the image.

If you're using virt-manager, the commands should look something like this:

# qemu-img create -f qcow2 /tmp/precise.qcow2 10G
# virt-install --virt-type kvm --name precise --ram 1024 \
--cdrom=/data/isos/precise-64-mini.iso \
--disk /tmp/precise.qcow2,format=qcow2 \
--network network=default \
--graphics vnc,listen=0.0.0.0 --noautoconsole \
--os-type=linux --os-variant=ubuntuprecise

At the initial Installer boot menu, choose the "Install" option. Step through the install prompts, the defaults should be fine.

The installer may ask you to choose a hostname. The default (ubuntu) is fine. We will install the cloud-init package later, which will set the hostname on boot when a new instance is provisioned using this image.

The default mirror proposed by the installer should be fine.

Step through the install, using the default options. When prompted for a username, the default (ubuntu) is fine.

There are different options for partitioning the disks. The default installation will use LVM partitions, and will create three partitions (/boot, /, swap), and this will work fine. Alternatively, you may wish to create a single ext4 partition, mounted to "/", should also work fine.

If unsure, we recommend you use the installer's default partition scheme, since there is no clear advantage to one scheme or another.

The Ubuntu installer will ask how you want to manage upgrades on your system. This option depends on your specific use case. If your virtual machine instances will be connected to the internet, we recommend "Install security updates automatically".

Choose "OpenSSH server"so that you will be able to SSH into the virtual machine when it launches inside of an OpenStack cloud.

Select "Yes" when asked about installing the GRUB boot loader to the master boot record.

Select the defaults for all of the remaining options. When the installation is complete, you will be prompted to remove the CD-ROM.

	Note
	When you hit "Continue" the virtual machine will shut down, even though it says it will reboot.

To eject a disk using virsh, libvirt requires that you attach an empty disk at the same target that the CDROM was previously attached, which should be hdc. You can confirm the appropriate target using the dom dumpxml vm-image command.

# virsh dumpxml precise
<domain type='kvm'>
  <name>precise</name>
...
    <disk type='block' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <target dev='hdc' bus='ide'/>
      <readonly/>
      <address type='drive' controller='0' bus='1' target='0' unit='0'/>
    </disk>
...
</domain>

Run the following commands in the host as root to start up the machine again as paused, eject the disk and resume. If you are using virt-manager, you may use the GUI instead.

# virsh start precise --paused
# virsh attach-disk --type cdrom --mode readonly precise "" hdc
# virsh resume precise

	Note
	In the example above, we start the instance paused, eject the disk, and then unpause. In theory, we could have ejected the disk at the "Installation complete" screen. However, our testing indicates that the Ubuntu installer locks the drive so that it cannot be ejected at that point.

When you boot for the first time after install, it may ask you about authentication tools, you can just choose 'Exit'. Then, log in as root using the root password you specified.

The cloud-init script starts on instance boot and will search for a metadata provider to fetch a public key from. The public key will be placed in the default user account for the image.

Install the cloud-init package:

# apt-get install cloud-init

When building Ubuntu images cloud-init must be explicitly configured for the metadata source in use. The OpenStack metadata server emulates the EC2 metadata service used by images in Amazon EC2.

To set the metadata source to be used by the image run the dpkg-reconfigure command against the cloud-init package. When prompted select the EC2 data source:

# dpkg-reconfigure cloud-init

The account varies by distribution. On Ubuntu-based virtual machines, the account is called "ubuntu". On Fedora-based virtual machines, the account is called "ec2-user".

You can change the name of the account used by cloud-init by editing the /etc/cloud/cloud.cfg file and adding a line with a different user. For example, to configure cloud-init to put the key in an account named "admin", edit the config file so it has the line:

user: admin

From inside the instance, as root:

# /sbin/shutdown -h now

The operating system records the MAC address of the virtual ethernet card in locations such as /etc/udev/rules.d/70-persistent-net.rules during the instance process. However, each time the image boots up, the virtual ethernet card will have a different MAC address, so this information must be deleted from the configuration file.

There is a utility called virt-sysprep, that performs various cleanup tasks such as removing the MAC address references. It will clean up a virtual machine image in place:

# virt-sysprep -d precise

Now that the image is ready to be uploaded to the Image Service, we no longer need to have this virtual machine image managed by libvirt. Use the virsh undefine vm-image command to inform libvirt

# virsh undefine precise

The underlying image file that you created with qemu-img create, such as /tmp/precise.qcow2, is now ready for uploading to the OpenStack Image Service.