Tuesday, April 04, 2006

Installing Linux to a USB hard drive

I recently purchased a Seagate 250GB hard drive and an Acomdata aluminum external hard drive USB/Firewire case. I use a nice Dell PC at work that only has Windows installed on it. Rather than trying to reformat and repartition this PC at work, I decided to attempt to install Ubuntu 5.10 to an external USB hard drive. This way, I can bring my own personal Linux distribution wherever I go and use it on any PC (given the motherboard supports booting from a USB device) without changing the contents of the PC's hard drive. I got this to work by following the instructions provided in this article:


In case this Ubuntu Forum post gets deleted, I have copied and pasted the appropriate steps below. My installation experience was slightly different from the original steps mentioned in the forum --I have indicated these differences with bold,italic, light-blue text.

Here is what I do to successfully load UBUNTU v5.10 on my EXTERNAL USB DRIVE ...

(Step 0 ) Plug the external USB drive into the computer. Unplug all of the internal IDE hard drives.

( STEP 1 ) Instead of using "expert" mode to install, I just hit enter to start the install process (using the install CD ... NOT the live CD).

INSTALL NOTE: The installation process will ask you for some information when it starts up ...

first it will ask for your language,
then your (language) location,
then your keyboard type,
then it will detect your cdrom(s),
then it will attempt to detect your network configuration,
then it will ask you to give your PC a name (hostname),
then it detects hardware and starts up the partition phase of the install.

INSTALL NOTE: When you get to STEP 2 (the partition phase), there is a simple way to determine how the install program assigns device names to your hard drive(s). Before starting any partitioning activity in STEP 2, choose the GO BACK option in the lower left corner of this screen and then choose EXECUTE A SHELL farther down in the Ubuntu installer menu that appears. Choose CONTINUE at the next prompt. In the shell window that appears, type in fdisk -l (that is FDISK -L in all lowercase). This will give you a list of all the storage devices the installer program sees. Make a note of the device names (/dev/hd? or /dev/sd?) and then type in exit to return to the partition phase (STEP 2) of the install. (Kudos to "RyanGT" for suggesting this in post #257.)

( Step 2 ) (ignore the Step 2 below) If you have a 250GB hard drive like I do, you probably don't want Ubuntu to create 3 giant partitions that span the entire drive. In fact, you will probably want to set up separate partitions manually. I set up my partitions as follows:

Filesystem Size Used Avail Use% Mounted on Fs
/dev/sda1 122M 19M 97M 17% /boot ext3
/dev/sda2 449M 255M 171M 60% / ext3
/dev/sda3 1.5G swap swap
/dev/sda5 95M 33M 62M 35% /tmp reiserfs
/dev/sda6 1.9G 492M 1.4G 26% /var reiserfs
/dev/sda7 1.9G 33M 1.9G 2% /usr/local reiserfs
/dev/sda8 5.6G 1.6G 4.1G 29% /usr reiserfs
/dev/sda9 28G 653M 28G 3% /home reiserfs

(note: I displayed this information by later typing "df -h" in a terminal window. sda4 is not present because it represents the extended partition
of the drive where sda5 - sda9 are within sda4)

I made sure that the /boot partition was small so that it does not exceed the first 1024 cylinders at the beginning of the hard drive --which I guess would make this partition not bootable.

skip this -- ( STEP 2 ) During the partitioning phase, I let the install program format my external USB drive. (I believe UBUNTU calls this a guided partitioning ... which sets up an ext2 or ext3 partition and a swap partition for you.)

INSTALL NOTE: Look for the line during the partitioning phase that might say ... erase entire disk SCSI (0,0,0) (sda). Be careful here as some people have had problems when choosing any partitioning options that include the text "and use LVM" (Kudos to "brucetan" for sharing this in post #268.)

Feel like learning about LVM anyway? Check this link out. (Kudos to "SD-Plissken" for sharing this info.)

BE VERY CAREFUL on these screens to choose the correct SDA drive and NOT an HDA drive or you may unintentionally format another drive in your system. There is no undo button for this!


( STEP 3 ) When the install gets to loading the GRUB bootloader ... DO NOT LET IT LOAD TO ANY OTHER DRIVE BUT THE EXTERNAL USB drive we are working with here. -- This doesn't matter since the other drives should be disconnected.

Say YES when asked if you want to install Grub to the MBR (since the USB drive is the only one connected --ignore where is says "say NO" below)
The install program will ask to load GRUB to the master boot record (MBR) of your internal hard drive (HDA). Say NO to this, and on the next screen, type in the correct path to the SDA (external USB) drive where we want to install the GRUB bootloader.
(Mine was /dev/sda [NOT sda1] ... but yours may be different depending on the number and/or types of drives in your system)

COMMENT: I loaded GRUB to sda (the bootsector of the external drive) and NOT to sda1 (which would be the first partition on the external drive).

INSTALL NOTE: at this point, the install program loads some stuff and ejects the CD ... wanting you to do a reboot.

( STEP 4 ) BE 100% SURE to leave the CD in the drive (and close the drive door) before rebooting. When the PC reboots, type in rescue (to load UBUNTU in rescue mode) ( Review REQUIREMENTS at the beginning of this guide! )

Why do we startup in rescue mode you might ask? It's because we have to edit a few files to get USB support loaded before UBUNTU actually gets going. And, we also need to change a setting in the GRUB menu file to make it work correctly.

( STEP 5 ) When the system comes back up it will ask for a partition to mount. Pick the correct mount point for your external drive from the list.
(Mine was mount /dev/discs/disc1/part1 ... but yours may be different depending on the number and/or types of drives in your system)

COMMENT: /dev/discs mount points start with disc0 (with 0 meaning the first drive in a system). So, my mount point of /dev/discs/disc1/part1 was really the second disk [disc1] (the sda drive we are working with) and the first partition [part1] on that disk.

( STEP 6 ) When it comes up to a terminal window (with RESCUE MODE in the upper left corner) and just sits there, hold down Ctrl-Alt-F2 to open another terminal window for us to do our edits in.

( STEP 7 ) Type in these lines before we start editing out files ...

mount -tproc proc /target/proc
chroot /target

INSTALL NOTE: I used vim to edit the files. (There is a great vim cheatsheet in pdf format available from "TimL".) It is weird to use at first until you learn what a few keys do in it. The INSERT key allows you to actually enter text where you place the cursor ... The ESC key takes you out of INSERT mode ... And hitting : x saves the file and exits out of vim. (IMPORTANT TIP ... that's a colon and a lowercase x with NO SPACE between the colon and the x)

( STEP 8 ) Run vim to edit the modules file to make sure USB support is added/loaded during UBUNTU startup ...

vim /etc/mkinitramfs/modules

Right below the last line of text, enter these lines ...


Be sure to save the file changes (using : x)

COMMENT: Some PCs may need a more comprehensive list added here. Please take a look at post #181 if you are having startup issues after these edits. (Kudos to "brotorious" for his efforts on this.)

( STEP 9 ) Run vim to edit the initramfs.conf file to make sure enough time elapses for USB support to load before UBUNTU gets running ...

vim /etc/mkinitramfs/initramfs.conf

At the very top of this file, add this line which tells UBUNTU to pause for 12 seconds before starting up ...

WAIT=12 (in all caps here, not sure if necessary though)

Be sure to save the file changes (using : x)

INSTALL NOTE: Editing these two files loads the necessary commands to get USB support going so UBUNTU will recognize the external USB drive. But we still need to recompile (or recreate) the initrd.img that UBUNTU uses at startup ... so that these edits actually work.

( STEP 10 ) Recompile (recreate) the initrd.img file to include USB support from these edited files ...

mkinitramfs -o /boot/initrd.img-2.6.12-9-386 /lib/modules/2.6.12-9-386

INSTALL NOTE: When you are done with the previous step #9 (and before performing this step), you can run the "ls /lib/modules" command (without the quote marks) from a terminal window to see what kernel version number you should use for this install step. They may be using a kernel version higher than 2.6.12-9-386 that was available when I originally created this help guide. (Kudos to "Saxegaard" for bringing this to my attention in post #235.)

Note: this entire step #11 might not be necessary if you disconnected the other hard drives from the computer. You may need to edit the "device.map" file though and make sure it contains the following line:
(hd0) dev/sda
If you DO end up having to edit menu.lst, make sure you type
"grub-install /dev/sda" (without the quotes of course) to update grub.

( STEP 11 ) Edit the GRUB bootloader menu file to correct a small error that looks at the wrong drive to boot from ...

vim /boot/grub/menu.lst

Navigate down this file until you get to a section where there is a menu list (not commented out ... no #s) that has Ubuntu mentioned three times (and possibly an area mentioning Windows XP down below it, if you have XP installed on an internal drive of yours).

There is a line in these three Ubuntu menu choices that has root listed on it and probably has (hd1,0) to the right of it. We need to change this to (hd0,0) on all three of these menu choices. Why? Because according to GRUB, the external USB drive will be our first drive (hd0,0) and not our second drive (hd1,0) because we loaded GRUB on it's bootsector.

INSTALL NOTE: You will also want to change a "# groot" line in a section of your menu.lst file that may look something like this ...
## default grub root device
## e.g. groot=(hd0,0)
# groot=(hd0,3) <<< groot="(hd0,0)"> until the screen actually says to press enter). Hold down Ctrl-Alt-F1 to get back to the RESCUE MODE terminal window and type exit to reboot the system.


( STEP 13 ) After rebooting, UBUNTU continues to run it's install process and comes to the desktop. Use the username and password you setup earlier in the install process to get into UBUNTU

That's the process I've successfully used to install UBUNTU v5.10 on an external USB drive. I hope this helps anyone whose been wrestling with this process. Let me know if it works out for you.


Reconnect all of your hard drives and boot up the computer. (make sure you tell your bios to boot from the USB drive)
If GRUB never loads and instead gives you an error message, then you may need to install GRUB to your main hard drive. Before doing this, try plugging in your USB drive into a different computer and see if it boots up. If you need to install GRUB to your IDE hard drive, then follow the steps in this article to trick the Ubuntu installer into skipping all steps and installing only the GRUB bootloader:


You can then copy the new kernel and initrd images you created in previous steps to the IDE hard drive and add them to the boot loader. To figure this out, I simply looked at other entries listed in the bootloader and applied this format to the new kernel and initrd images.


* Booting Ubuntu from Windows XP without loading GRUB to the MBR ...
(Kudos to "celticmonkey" for documenting this.)

* Problems booting XP from an internal drive ...
( message #2 ) + ( message #203 )

* Problems starting UBUNTU after a kernel update using Ubuntu's automatic update app ...
( message #112 ) + ( message #161 )

* Using Windows XP to format drives larger than 32GB AS FAT32 ...
( message #188 )

* Re-installing GRUB in a relatively painless manner ...
( message #205 ) (Kudos to "RyanGT" for hunting this down.)

* Creating a bootable GRUB CD (sketchy details but seems to make sense) ...
( message #207 ) + http://www.gnu.org/software/grub/man...D_002dROM.html


* GRUB Manual (section 14.3 shows what error codes mean)
( If you don't care who gets the credit ... great things can be accomplished. )
Setup Guide: "Installing Ubuntu on an external USB Drive"
Good Starter Book: "Linux Desktop Pocket Guide"


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