Linux 2005

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CACert Assurance

Thursday Evening

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Fabian Franz - University of Karlsruhe

UnionFS: Knoppix (Re)writable

Starting with version 3.8, Knoppix is using UnionFS. This means that you can work with the CD as if it had been installed to your local hard disk. You can for example delete or install new programs without any additional tweaking of the setup. Just use apt-get install <my-new-program>...

Once you are satisfied with the personalisation of your system you can create snapshots to stress-test the new software. If you don't like it, just reboot and no changes have been made at all!

UnionFS can stack several file system trees over each other, creating the appearance (to the user as well as the operating system) of being one and the same (unioned/unified/merged) tree. Some of its sub-trees may be "mounted" read-only, others may be "mounted" read/write.

Using UnionFS is very easy and convenient. But still there are lots of settings that can be tuned. It is not just suitable for revolutionizing Knoppix and the way Live-CDs work. It could also revolutionize the way we are working with our standard systems. The developers of the "Plan 9" operating system have known this for years - they had UnionFS in their system since day 1.

Imagine for example just having /bin and all programs including user installed programs available there, so whether your <myprogram> is stored in /usr/bin/, in /usr/local/bin/ or in $HOME/bin, you can acess it via the same /bin/<myprogram> path.

Some of Plan 9's revolutionary ideas now come back to Linux.

The talk shows in a live demonstration how UnionFS is used in Knoppix. It discusses the many exciting possibilites, which are now open to the world. For example:

• Write the changes to a CD-RW after shutdown;
• Install programs with just one click to evaluate them;
• Make dynamic (S)FTP servers available, without a need to copy data at all.

If there is interest, the talk will also explain some of the technical concepts behind UnionFS and why it is a good solution from a developer's point of view.