Ubuntu JeOS (pronounced "Juice") is an efficient variant of the Ubuntu Server operating system, configured specifically for virtual appliances. No longer available as a CD-ROM ISO for download, but only as an option either:

JeOS is a specialized installation of Ubuntu Server Edition with a tuned kernel that only contains the base elements needed to run within a virtualized environment.

Ubuntu JeOS has been tuned to take advantage of key performance technologies in the latest virtualization products from VMware. This combination of reduced size and optimized performance ensures that Ubuntu JeOS Edition delivers a highly efficient use of server resources in large virtual deployments.

Without unnecessary drivers, and only the minimal required packages, ISVs can configure their supporting OS exactly as they require. They have the peace of mind that updates, whether for security or enhancement reasons, will be limited to the bare minimum of what is required in their specific environment. In turn, users deploying virtual appliances built on top of JeOS will have to go through fewer updates and therefore less maintenance than they would have had to with a standard full installation of a server.

With vmbuilder, there is no need to download a JeOS ISO anymore. vmbuilder will fetch the various package and build a virtual machine tailored for our need in about a minute for us. Vmbuilder is a Script that automates the process of creating a ready to use Linux based VM. The currently supported hypervisors are KVM and Xen.

You can pass command line options to add extra packages, remove packages, choose which version of Ubuntu, which mirror etc. On recent hardware with plenty of RAM, tmpdir in /dev/shm or using a tmpfs, and a local mirror, you can bootstrap a VM in less than a minute.

First introduced as a shell script in Ubuntu 8.04LTS, ubuntu-vm-builder started with little emphasis as a hack to help developers test their new code in a virtual machine without having to restart from scratch each time. As a few Ubuntu administrators started to notice this script, a few of them went on improving it and adapting it for so many use case that Soren Hansen (the author of the script and Ubuntu virtualization specialist, not the golf player) decided to rewrite it from scratch for Intrepid as a python script with a few new design goals:

But the general principles and commands remain the same.

The name of the package that we need to install is python-vm-builder. In a terminal prompt enter:

sudo apt-get install python-vm-builder

vmbuilder --help

As this example is based on KVM and Ubuntu 8.10 (Intrepid Ibex), and we are likely to rebuild the same virtual machine multiple time, we'll invoke vmbuilder with the following first parameters:

sudo vmbuilder kvm ubuntu --suite intrepid --flavour virtual --arch i386  -o --libvirt qemu:///system

The --suite defines the Ubuntu release, the --flavour specifies that we want to use the virtual kernel (that's the one used to build a JeOS image), the --arch tells that we want to use a 32 bit machine, the -o tells vmbuilder to overwrite the previous version of the VM and the --libvirt tells to inform the local virtualization environment to add the resulting VM to the list of available machines.

Notes:

In this example we will be installing a package (Limesurvey) that accesses a MySQL database and has a web interface. We will therefore require our OS to provide us with:

This is done using vmbuilder by specifying the --addpkg command multiple times:

--addpkg PKG
  Install PKG into the guest (can be specfied multiple times)

However, due to the way vmbuilder operates, packages that have to ask questions to the user during the post install phase are not supported and should instead be installed while interactivity can occur. This is the case of Limesurvey, which we will have to install later, once the user logs in.

Other packages that ask simple debconf question, such as mysql-server asking to set a password, the package can be installed immediately, but we will have to reconfigure it the first time the user logs in.

If some packages that we need to install are not in main, we need to enable the additional repositories using --comp and --ppa:

--components COMP1,COMP2,...,COMPN
           A comma separated list of distro components to include (e.g. main,universe). This defaults
           to "main"
--ppa=PPA  Add ppa belonging to PPA to the vm's sources.list.

Limesurvey not being part of the archive at the moment, we'll specify it's PPA (personal package archive) address so that it is added to the VM /etc/apt/source.list, so we add the following options to the command line:

--addpkg apache2 --addpkg apache2-mpm-prefork --addpkg apache2-utils --addpkg apache2.2-common \
         --addpkg dbconfig-common --addpkg libapache2-mod-php5 --addpkg mysql-client --addpkg php5-cli \
         --addpkg php5-gd --addpkg php5-ldap --addpkg php5-mysql --addpkg wwwconfig-common \
         --addpkg mysql-server --ppa nijaba

As you can easily imagine, writing to RAM is a LOT faster than writing to disk. If you have some free memory, letting vmbuilder perform its operation in a RAMdisk will help a lot and the option --tmpfs will help you do just that:

--tmpfs OPTS  Use a tmpfs as the working directory, specifying its
              size or "-" to use tmpfs default (suid,dev,size=1G).

So adding --tmpfs - sounds like a very good idea if you have 1G of free ram.

As we mentioned earlier, the first time the machine boots we'll need to install openssh-server so that the key generated for it is unique for each machine. To do this, we'll write a script called boot.sh as follows:

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

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

And we add the --firstboot boot.sh option to our command line.

Mysql and Limesurvey needing some user interaction during their setup, we'll set them up the first time a user logs in using a script named login.sh. We'll also use this script to let the user specify:

So we'll define login.sh as follows:

# This script is ran the first time a user logs in

echo "Your appliance is about to be finished to be set up."
echo "In order to do it, we'll need to ask you a few questions,"
echo "starting by changing your user password."

passwd

#give the opportunity to change the keyboard
sudo dpkg-reconfigure console-setup

#configure the mysql server root password
sudo dpkg-reconfigure mysql-server-5.0

#install limesurvey
sudo apt-get install -qqy --force-yes limesurvey

echo "Your appliance is now configured.  To use it point your"
echo "browser to http://serverip/limesurvey/admin"

And we add the --firstlogin login.sh option to our command line.

To have your system be configured to update itself on a regular basis, we will just install unattended-upgrades, so we add the following option to our command line:

--addpkg unattended-upgrades

As we have put our application package in a PPA, the process will update not only the system, but also the application each time we update the version in the PPA.

For your virtual machine to be able to handle restart and shutdown events it is being sent, it is a good idea to install the acpid package as well. To do this we just add the following option:

--addpkg acpid