Booting from a USB device

There are various reasons for which you might want to consider booting from a usb. The recent trend in using net-books has made this very necessary as most net books do not contain an in-built CD-ROM. Hence, the only options one has, is, to either buy an external CD-ROM with an external USB interface and carry this CD ROM wherever you go or be smart and learn to do everything using a USB. In fact, the primary motivation for me to learn to boot from a USB was to install a linux operating system on my friend's assus netbook. Please note that before you start you must first ensure that the computer in question actually supports booting from a USB and you may have to change Bios settings appropriately.

This post explains how to replicate an iso file of any Operating system (preferably one of the linux distros) into a bootable partition of a USB device. I have successfully installed operating systems on a USB partition using Ubuntu 8.04 as well as Ubuntu 9.04.

If you can install unetbootin then do use it and forget about the rest of this post as unetbootin is an amazing tool to get the job done. However, even for unetbootin, you need to first create a bootable partition on the USB device which I have explained in my previous post. So, before you proceed to use unetbootin, I would suggest that you first create a bootable partition on the USB by referring here.

As for those who do not have Unetbootin or cannot install it, the following steps will help you to replicate any .iso file into a bootable partition of your USB hard disk:

1. Prerequisites
   • syslinux tools

       $sudo apt-get install syslinux 
     

   • Create a bootable partition on your USB
     

     Please refer to my previous post where I have used gparted to get the job done. It is the easiest way and least error-prone.

   • Download this script (which did not work on Ubuntu 9.04):

       wget http://zelut.org/projects/misc/isotostick.sh
     

     Make it executable with the command:

       $chmod u+x isotostick.sh
     

2. Run the script isotostick.sh downloaded in the previous step.
   It requires two arguments, the .ISO file and the bootable partition on the USB device. This step may take some time depending on the speed of the usb and your machine among other things, so please be patient and allow it to run in the background.

     $sudo ./isotostick.sh /path/to/your.iso /dev/sdXn
   

   Note that the second argument may vary depending on the location of the bootable partition.
   The command I used is as given below.

     $sudo ./isotostick.sh iso/ubuntu-8.10-desktop-i386.iso /dev/sdb3
   

3. Make sure its bootable with syslinux:

           $sudo syslinux /dev/sdXn
   

   So, I had to run

           $sudo syslinux /dev/sdb3
   

That's it !!!

You are now ready to boot the newly installed Operating System from the bios prompt.