Using Ubuntu cloud-images without a cloud

Since sometime in early 2009, we've put effort into building the Ubuntu cloud images and making them useful as "cloud images". From the beginning, they supported use as an instance on a cloud platform. Initially that was limited to EC2 and Eucalyptus, but over time, we've extended the "Data Sources" that the images support.

A "Data Source" to cloud-init provides 2 essential bits of information that turn a generic cloud-image into a cloud instance that is actually usable to its creator. Those are:

• public ssh key
• user-data

Without these, the cloud image cannot even be logged into.

Very early on it felt like we should have a way to use these images outside of a cloud. They were essentially ready-to-use installations of Ubuntu Server that allow you to bypass installation. In 11.04 we added the OVF as a data source and a tool in cloud-init's source tree for creating a OVF ISO Transport that cloud-init would read data from. It wasn't until 12.04 that we improved the "NoCloud" data source to make this even easier.

Available in cloud-utils, and packaged in Ubuntu 12.10 is a utility named 'cloud-localds'. This makes it trivial to create a "local datasource" that the cloud-images will then use to get the ssh key and/or user-data described above.

After boot, you should see a login prompt that you can log into with 'ubuntu' and 'passw0rd' as specified by the user-data provided.

Some notes about the above:

•  None of the commands other than 'apt-get install' require root.
•  The 2 qemu-img commands are not strictly necessary. 
• The 'convert' converts the compressed qcow2 disk image as downloaded to an uncompressed version.  If you don't do this the image will still boot, but reads will go decompression.
• The 'create' creates a new qcow2 delta image backed by 'disk1.img.orig'. It is not necessary, but useful to keep the '.orig' file pristine. All writes in the kvm instance will go to the disk.img file.
• libvirt, different kvm networking or disk could have been used. The kvm command above is just the simplest for demonstration. (I'm a big fan of the '-curses' option to kvm.)
• In the kvm command above, you'll need to hit 'ctrl-alt-3' to see kernel boot messages and boot progress. That is because the cloud images by default send console output to the first serial device, that a cloud provider is likely to log.
• There is no default password in the Ubuntu images. The password was set by the user-data provided.

The content of 'my-user-data' can actually be anything that cloud-init supports as user-data.  So any custom user-data you have can be used (or developed) in this way.