In a previous article I mentioned that a livecd image booted from a USB flash drive is not the same as a Linux distribution installed to a flash drive. This article will explore that idea in a a little more detail. There is a website, pendrivedrivelinux.com, that contains numerous tutorials on how to create a bootable flash drive with livecd images. The unetbootin utility, available in both a Windows and Linux version further simplifies the process. To fully understand what we are doing we must first understand how a livecd does its magic.

In order to fit on a 700MB CD the burnable .iso image cannot be larger. When installed to a hard drive a typical distribution, such as Ubuntu, uses over 2GB of disk space. To make this possible a compression technique is used. When the image is used it is read from the disc and uncompressed on the fly. This has several implications. The two most noticeable will be that using a livecd will be slower than using an installed distro; the second is that no changes can be made to the CD. At best, some documents may be saved to a local hard disk and some distros such as Puppy Linux can create a change file.

The use of a flash drive may or may not remove some of the livecd limitations depending on its size. Today, in the spring of 2009, you will have difficulty finding a flash drive with less than 1GB of memory that were common only a few years ago. 1GB drives sell for around $5, 2GB drives are priced at $10 or less and higher capacities of 4, 8 and 16GB are often on sale bringing the price down to less than $3 per GB. In a year or two, readers of this blog will probably chuckle at these prices. If you have a 2 or 4GB drive the tutorials at pendrivelinux.com will show you how to (1) get the iso image onto a bootable drive and (2) how to use the extra space for data or a “change” file. If you have a 4GB or larger drive it is now possible to make a full installation to the drive. This removes both limitations of the livecd. Most recent releases of popular distros include an option to install to a sufficiently large flash drive. Furthermore, netbooks can boot from these drives making it possible to replace the supplied OS (often Windows XP) with the Linux distro of your choice. Finally we now have a portable computer with a reasonably sized screen that will run for a number of hours between charges.

Now before you run out and buy that 8GB stick I will give you two cautions. The first caution is that once you configure your drive to use your host computer hardware you may lose compatibility with other computers. If portability is your objective an installed OS might not be your best choice. I personally carry a 2GB drive with Puppy installed but not configured along with a GRUB boot disk. At home, I keep a 8GB drive handy to install various test distributions one of which will eventually end up in the netbook I have on order for this summer. Yes, I could do the same thing with a “virtual machine” but this approach is simpler and takes up no space on my hard disc.

The second caution is about following the tutorials on pendrivelinux.com. Many make the use of a disc “partitioning” utility, either fdisk, on the command line,  or Gparted with its nice graphical interface. It is VERY EASY to make a MISTAKE with these utilities to select a WRONG drive and DESTROY your system!  Do not proceed with the instructions until you understand what they are doing and what they are doing it to. Linux drive designations can be cryptic to the novice. If you have a small flash drive and just want to make it bootable then use unetbootin and be safe. Enough said.

Have fun!