Booting Ubuntu To RAM

Booting Ubuntu To RAM is an article aims to document the process of creating a customized Ubuntu that loads an image from the hard disk to RAM, then boots an entire Ubuntu session out of RAM. It is intended for intermediate to advanced Ubuntu users who are familiar with the shell, and may have limited experience customizing the livecd (LiveCDCustomization) and shell scripting. We will customize a LiveCD and copy it to the hard drive, and make a few modifications to bootup scripts so that it copies to RAM via our good friend tmpfs.
WARNING: The author asserts that this procedure works for him, but cannot guarantee that this procedure works for anyone else. Although this procedure is meant to be 100% safe, it is feasible that there may be mistakes, or a chance of misunderstanding the instructions in a manner that causes loss of data. Please make a backup and do not attempt on mission critical systems. Read through this article thoroughly, and do not attempt if you do not comprehend or feel comfortable about any of the instructions!
CAUTION: I hope this is intuitively obvious, but Ill humor you and state it bluntly: Changes you make under the live session are NOT saved and WILL BE LOST when you reboot or shut down. Dont save anything important to the "home directory" and expect it to still be around! If you want to save data permanently, mount a permanent medium (such as your hard drive), plug in a thumbdrive, or use some network functionality built into Ubuntu to save your data to a non-volatile destination.
There are many cases where one would like to boot Ubuntu to RAM:
- Performance: The desktop performance is dramatically improved. A 400MB squashed filesystem in RAM, that holds 1200MB of data, is read back on a 1.6GHz Core Duo in about 3 seconds, including decompression time.
- Power, Noise, Durability: Although modern hard disks dont use much power compared to other system components, this may still be important for some. In laptops, hard disks are often the noisiest components, so this setup can reduce system noise. With the hard disk spun down, a laptop can potentially withstand greater shocks without damage.
- Abrupt poweroff: Since the hard disk is only momentarily used in read-only mode during boot, then never touched again, there are few or no negative consequences of an abrupt poweroff. If a system is used where power is inconsistent, or the system is regularly used in a context where fast shutoffs are required, this is very handy.
- Privacy: Anything you do in this session are lost when you reboot or power off. This is great for kiosks or other systems where permanent modification are not desired. (Note that by default the livecd user has full sudo access, so potentially a malicious user can still make permanent changes by mounting the hard drive and following this HOWTO)