USB Booting

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Contents

Introduction

USB booting is running an OS off a pen drive or other USB mass storage device. It can be a hit-or-miss process with any pendrive-based operating systems, but sometimes it's worth being able to USB boot. This page should help you find out:

  • whether your computer supports USB booting (or how to find out)
  • how to turn on support if you've got it
  • your options if you don't get it, or if it doesn't work (USB boot floppy, USB via GRUB, etc)

Read on, explorer ...

Installing to USB

There's a lot of wiki dedicated to Installing to a USB Flash Drive. If you want to know about installing, start there.

BIOS Limitations

Older computer BIOSes (pre-2001) usually do not support booting from a USB device. Around 2001, PC motherboard manufacturers started to add USB boot support.

There are two common BIOS methods for direct USB booting:

  • The "USBHDD" method boots a USB mass storage device that is configured like a normal PC hard drive.
  • The "USBZIP" method supports booting from a USB storage device that behaves like the original IOMEGA ZIP drive with USB support.

Most computers (just about all Dells, for example) made today (2006+) have a BIOS that supports the USBHDD method so I expect that this will eventually become the standard way to boot a USB device. However, many motherboards will support BOTH methods, and many older motherboards have USBZIP support.

Some newer BIOSes support USB 2.0 but will not boot from an older pen drive. Using a USB 2.0 compliant one usually solves this problem. Also, some BIOSes which support USB 1.1 will not boot the newer, USB 2.0 drives!

If your computer does not recognize a USB pen drive of 500+ MB, it is possible that the motherboard has the recognition set to "auto", which means it will treat pen drives less than 500MB as "Floppy", and greater than 500MB as USBHDD. Try to find the option "Force FDD" in your BIOS setup. This should allow your pen drive to be treated as USBZIP no matter its size.

Enabling BIOS Support

Warning: You can mess up your computer by setting the BIOS the wrong way. Be careful, write down any changes to make sure you can restore them. Don't play with the hard drive settings. Be safe. Enough said.

1. Try it: Most modern (2006+) computers will have USB support turned on automatically. Try it out first (just leave in your bootable stick, and reboot). If it works - you're golden.

2. Enter BIOS Setup. If your computer ignores your USB drive, then you're not out of luck yet. When your system turns on, you have a few seconds to enter the BIOS setup program. Just after booting, press whatever keys the BIOS asks for when it says "Press [keys] to enter BIOS setup". If your computer doesn't prompt you, search Google for your particular model. Esc, F1, F2, F3, F10, and F12 are common entrance keys for entering BIOS setup. If you can't get into BIOS setup ... you're stumped for now. Try an alternative boot method below (floppy or GRUB).

3. Alter your BIOS Setup: Your BIOS setup screen will be unique to your BIOS version. Look for a menu item that includes the motherboard boot order, boot devices, or 'alternative boot' methods. If you don't find anything that says USB ... read below for an alternative boot method (floppy, GRUB). If you do, play with the settings a bit and reset.

Keep trying. If you've got USB support, you can probably make it work.

Boot floppy

Just about any computer that has an available USB port and a floppy drive will support booting from the DSL USB boot floppy. See the boot floppy section for more info.

USB Booting from GRUB

If you have GRUB installed on your hard drive, you can boot DSL from that GRUB installation without altering your BIOS settings. You could investigate by yourself what options to add, but with this you should be fine. Note that if GRUB is protected with password, you need that or you can't follow this procedure.

When you are on the GRUB screen, press c, then write the following: 

       grub > root (hdX,Y)

       grub > kernel /linux24 root=/dev/sdZN init=/etc/init

       grub > initrd /minirt24.gz

       grub > boot

Where X is your usb stick and Y a partition number starting with 0. You can press the tab key from your keyboard to see a list of available disks, as in the following: 

       hd0, hd1, ...

You can also guess, if you don't know which hd above is your pen, by pressing tab again after choosing one of the hd0, hd1,..., etc. Another list will show up with the partition information of the selected disk, numbered starting with 0. That number, that corresponds to a partition, is the Y named above. You can do this with all the devices and then conclude which one is your pen.

Generally speaking (if you don't need to map your devices) Z will be a letter as follows:

  • Suppose that you have a list of available devices: 
       hd0, hd1, ..., hdN
  • Start counting with letters starting with a from the first sata disk (if there is one) to the pen drive. The letter you reach is the Z you replace. Note that if there aren't any sata disks, Z will be a.

And last, N will be N = Y + 1.

Example: Suppose you have two disks: a primary pata, and a secondary sata. You boot your pc, and insert the pendrive. Suppose also that hd0 is your primary disk, hd1 your secondary disk, and hd2 your pen. Then, our Z will be b as a is the secondary disk hd1, which is sata.


External links

Retrieved from "http://damnsmalllinux.org/wiki/index.php/USB_Booting"