Ubuntu 10.4 Full Disk Encryption

Is it possible to setup full disk encryption for Ubuntu 10.4 server? Either natively or with Truecrypt?

Additionally, is this something that has to be done at the time of installing the OS, or can it be done afterwards?

Ubuntu has supported install-time encryption using LUKS since at least 8.04. Use the alternate installer.

Correct me if I am wrong but I believe it is highly recommended to perform a full disk encryption at the time of installation/before you start dumping 'real' data on the disk due to the fact that the encrypted form is 'simply' placed over the layer in which your data is/was stored. i.e. Using a method such as magnetic force microscopy, it may be possible (although highly unlikely) to retrieve the data that was overwritten with its encrypted form.

I am adding this as an alternative answer:

https://mknowles.com.au/wordpress/2009/12/02/ubuntu-karmic-koala-9-10-%E2%80%93-full-disk-encryption-with-usb-key-authentication-v2/

This is pretty slick because it allows you to store the key on a USB drive. The downside is that you have to encrypt the disk 1st, before you use it.

We use WinMagic around my office for all of our machines. It's FDE and supports Windows, OS X, and Linux.

http://www.winmagic.com/products/linux-securedoc-disk-encryption