Booting up Linux from a USB flash drive

Overview

This little tutorial will help you to boot Linux from a USB flash drive. Why do you need that? A couple of ideas:

1) you can carry Linux with you everywhere
2) you can use it to fix/rescue data from a corrupted hard disk

Let's start!

What is a USB flash drive? According to Wikipedia: 'A USB flash drive is essentially NAND-type flash memory integrated with a USB 1.1 or 2.0 interface used as a small, lightweight, removable data storage device of up to 16 GB (as of 2006).' (http://en.wikipedia.org/wiki/USB_Flash_Drive). USB flash drives have less storage capacity than an external hard drive, but they are smaller and more durable because they do not contain any internal moving parts. To know more about USB flash drives (they are also known as 'USB keys', 'pen drives', 'key drives', 'thumb drives' 'flash memory drive' and many other names), take a look at:

http://www.usbflashdrive.org/usbfd_faq.html

Booting up Windows from a USB flash drive is not recommended as Windows needs to write into the booting medium during boot and USB flash drives have limited write cycles (about 1,000,000 times, but please notice that may not mean to each memory cell, so a common USB flash drive life may be shorter, let's say as low as 50,000 writes). What about booting up Mac Os X from a USB flash drive? Well, notice that booting from USB devices with Macintosh computers is a troublesome thing. Apple says that:
'If you select a USB startup disk from System Preferences, in some cases the computer may not start up from the USB disk. This is expected behavior. Under Mac OS X, Apple does not support starting up from USB devices. Although some configurations may allow a USB volume to be selected as a startup volume via the Startup Manager, this may not work for all configurations, and Apple is unable to provide assistance in troubleshooting such configurations.' In fact, booting from a USB flash drive is a procedure working on PCs and non-powerpc notebooks *ONLY*. If you are a Mac user like me, please consider a Firewire flash drive instead. The only Firewire flash drive I know is that sold here:

http://www.kanguru.com/fireflash.html

(but you can have better luck googling).

Well, let's go back to what I was saying about Linux on a USB flash drive. To succeed in that, some requirements are needed:

1) a mainboard with a USB connector (of course ;o)
2) a BIOS supporting boot from USB devices
3) a Formatted USB device that comply to USB standard

Please, make sure that your computer supports booting from USB devices. Most of troubles are caused by computers not supporting boot from USB devices. As said before, you need a USB flash drive that comply to USB standard. As a rule of thumb, get a USB flash drive that can be recognized by Windows XP or Windows 2000 *WITHOUT* any supplied driver. In other words, look at the USB device's package: it must state that it works on Windows and no installation CD ROM must be required. I suggest you a 256 Mb USB flash drive (but a 128 MB flash drive works fine too). About BIOSes supporting boot from USB devices, I couldn't find any BIOS-supporting-boot-from-USB list but, as usual, you can have better luck googling.

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