How to create an external USB bootable Linux hard drive (without dual-boot)

The topic of a bootable external USB Linux hard drive (without dual-boot) is an area that is not well documented. A simple Google search shows many articles, blogs and forum posts written on this topic, all of them discuss setting up dual-boot strategies. While I did not specifically test a USB Thumb Drive and did not intend to address this device in this article, I see no reason why this would not work for Thumb Drives as well. This article was written with the goal of defining an alternative to the traditional dual boot concept and keeping each operating system isolated from each other.

While the dual-boot scenario works, this can cause undesirable issues when grub installs its files on the external drive. Should Grub install its files to the external drive, the drive must be connected before booting the computer or you will receive a Grub 17or 21 error. Based on the testing I have done in an effort to achieve the desired results, I did not want a dual-boot on either the laptops operating system (internal hard drive) or on the external USB drive.

This document applies to SLES 10 SP1, SLED 10 SP1, OpenSUSE 10.3; however based on my testing I feel that this will work with any Linux distribution. You will want to use laptop or desktop hardware in which the BIOS supports booting to a USB device.

 

Why would you want to do this?

 

Small foot print USB powered external drives are very obtainable and affordable. These drives come in various sizes with the most common and cost effective today being 250GB. This gives you the ability to:

 

1. Test new OS versions

2. Carry multiple working OS’s with you in the field

3. Lab issues in the field

4. Test patches

5. Perform demonstrations

All of the above and more without risking the OS installed in your laptop or desktop. While this solution may not be right for everyone; this will provide you with more options.

There are several ways to achieve the results described herein; I will describe two of these methods and you can choose which method works better for your scenario.

 

Method 1:

1. Insert the Linux OS Install CD/DVD
2. Reboot the computer
3. Enter the “Setup Menu"
4. Disable the internal hard drive
5. Save settings and exit
6. The computer will reboot so you can see the Post Screen
7. Push the appropriate key (F12 for Dell Laptops) to bring up the “One Time Boot Menu”
8. Select boot from CD/DVD
9. Install Linux OS (Follow your normal install procedure)
10. The only device that should appear is the external USB drive

 

Note:
Since the internal hard drive is disabled the Linux OS will have no choice, it will install all of the required components for the external USB drive to become a bootable device.

 

When the install has completed:

1. Remove the Linux OS Install CD/DVD
2. Reboot the computer
3. Enter the “Setup Menu"
4. Enable the internal hard drive
5. Change the boot order to resemble

a.USB Device

b.Internal Hard drive

c.CD/DVD

6. Save settings and exit
7.The computer will reboot so you can see the Post Screen (Let the system boot as normal)

 

The machine will boot into your newly installed Linux OS and will have no knowledge or connection to the OS that is installed on the computers internal hard drive.

 

Method 2:

 

1. Insert the Linux OS Install CD/DVD
2. Shut down the computer
3. Remove the internal hard drive
4. Start the computer
5. The computer will boot so you can see the Post Screen
6. Push the appropriate key (F12 for Dell Laptops) to bring up the “One Time Boot Menu”
7. Select boot from CD/DVD
8. Install Linux OS (Follow your normal install procedure)
9. The only device that should appear is the external USB drive

 

Note:
Since the internal hard drive was physically removed the Linux OS will have no choice, it will install all of the required components for the external USB drive to become a bootable device.

 

When the install has completed:

1. Remove the Linux OS Install CD/DVD
2. Shut down the computer
3. Install internal hard drive
4. Enter the “Setup Menu”
5. Change the boot order to resemble

a.USB Device

b.Internal Hard drive

c.CD/DVD

6. Save settings and exit
7. The computer will reboot so you can see the Post Screen (Let the system boot as normal)

The machine will boot into your newly installed Linux OS and will have no knowledge or connection to the OS that is installed on the computers internal hard drive.

 

Issue:

During one of my tests, after all of the above steps were completed Linux on the USB External Hard drive would not boot. The computer did not see the device as a bootable device therefore the machine booted to the OS installed on the internal hard drive.

 

Solution:

1. Plug the external USB device into the USB port on the computer
2. Place the Linux install CD/DVD in the CD/DVD drive on the computer
3. The computer will boot so you can see the Post Screen
4. Push the appropriate key (F12 for Dell Laptops) to bring up the “One Time Boot Menu”
5. Select boot from CD/DVD
6.The main install screen will give you the option to repair the Installed OS (during my tests this did not have any unwanted effects on the computers internal hard drive or the OS installed on it)
7. Once the repair is completed remove the CD/DVD from the CD/DVD drive
8. Reboot the computer

The computer should boot to the OS installed on the external USB drive without issue. However you need to understand the BIOS in your machine.

In some cases you may want to remove any USB devices except for the hard drive until after the computer completes it's initial boot.