Booting from USB Drives?

GilesP asks: "With so many USB flash drives around (like the pendrive, Targus Go-Anywhere, and others), and with the demise of the floppy disk, I began to wonder if it would be possible to boot from a USB drive? So your BIOS is going to need to support booting from a USB device, but what else would be involved? I'm primarily thinking about Linux here, but other OSes would be interesting too. These devices come in a range of sizes from 8Mb up to 1Gb, so there is plenty of room to hold a Linux installation. Has anybody done anything like this?"

Comments

booting from pendrive

[xFallenAngel]

All you need to do is to tell your bios to boot
from USB, as long as your bios allows this.

Then just install a system on the pendrive,
kernel and all, usb support compiled in.
That should be sufficient. rdev/lilo as needed

-Fallen

Re:booting from pendrive

[GoRK]

Ehrm, no.

OK, here is the real answer.

Some pc BIOS can boot off of an ATAPI device hooked to USB, such as an Iomega Zip drive or a compact flash card or somesuch; however, the implementations vary WILDLY on how this is accomplished. Booting from said devices involves much fakery in what is usually presented to a bootloader as either a virtual floppy drive or a virtual hard disk. The fakery involved in booting from USB is even more complicated than booting from a CD-ROM, for which there is (at least) a standard that most bioses somewhat support.

Your bootloader (lilo, grub, etc.) can indeed bootstrap the kernel from a USB connected boot media; however, you will have to configure it differently based on which kind of device (floppy or HDD) your bios simulates for a USB boot. IE if your bios simulates a floppy drive, you'll have to tell lilo/grub/etc to load the kernel from the bios's floppy drive (here, bios calls to the floppy drive are rerouted to the usb device). Incedentally, this is the way CD-ROM booting works, but CD-ROM booting is MUCH simpler since an image file in a special area of the CD-ROM sits in for the virtual drive.

Anyway, most USB booting bioses are going to be simulating hard drives anyway due to the size of most usb media, so all you have to do is set up lilo to boot from the first bios hdd (ie 0x80) and you're set there.

Now on the subject of actually bringing the OS up - well that is the fun part. You can not (as the parent post said) just have "usb support compiled in" to make linux boot. USB doesnt exactly work that way in Linux. You can indeed have your usb controller driver, the usb mass storage driver, etc. all compiled statically with the kernel (not modules), but you're still going to have to start the hotplug daemon to get the setup functional to where you can use the connected device, and that's not going to happen without a root filesystem.

So, you need an initrd. No problem provided you can get lilo or grub or whateverelse to find and load it. All your initrd needs to do is to load up your USB modules, mount your root fs off of usb mass storage (/dev/sda1 or whatever weird devfs name you use) and then pivot_root over to it. This is mostly equivalent to an initrd setup for something like a network booting system that uses NFS root or fibre channel or something like that. Any initrd HOWTO will cover setting up an initrd that loads modules and performs configuration to mount the root device that the kernel cannot do on its own.

Sorry for the long ramble. Booting linux from USB is possible; however, it is not for the faint of heart. If you get it to work, it will probably not work for every motherboard that claims to allow usb booting. Any modern version of Windows will most not boot this way. (Well, technically you could load windows 3.11 or earlier in real mode like this, and maybe even windows 95/98 in safe mode)

FYI, a good place to start looking is the HOWTO's that involve installing linux onto subnotebooks without internal CDROM or Floppy. A lot of these sites provide floppy images that can boostrap an installation system (ie linux) from a USB connected floppy or cdrom drive. The USB booting on these laptops is probably quite a bit more solid than the equivalent on any desktop motherboard.

~GoRK

Re:booting from pendrive

[disappear]

So, you need an initrd. No problem provided you can get lilo or grub or whateverelse to find and load it. All your initrd needs to do is to load up your USB modules, mount your root fs off of usb mass storage (/dev/sda1 or whatever weird devfs name you use) and then pivot_root over to it. This is mostly equivalent to an initrd setup for something like a network booting system that uses NFS root or fibre channel or something like that. Any initrd HOWTO will cover setting up an initrd that loads modules and performs configuration to mount the root device that the kernel cannot do on its own.

You missed a step:
The initrd has to have about a one-second delay before you attempt to mount the drive from USB. This is because it takes a little while to detect it.

If you make this one change (a little static binary that does 'sleep 1', essentially) to a standard Red Hat 'mkinitrd' ramdisk, you can indeed do USB if your BIOS supports it.

I've done it. It was a @!#$% to debug the first time around: every time I dropped into sash everything worked, but if I didn't drop into sash it didn't. :-)

Re:booting from pendrive

[randombit]

I've done it. It was a @!#$% to debug the first time around: every time I dropped into sash everything worked, but if I didn't drop into sash it didn't. :-)

Ah, good times messing with free Unix systems. :)

This is totally offtopic to the article. I just thought of a little story that was somewhat related to yours. Once, long ago (OK, 4 or 5 months ago) hacking the Linux VM for an OS class. An editing error (I cut some code to move it around, and ended up pasting it twice in two different spots) completely broke shared libraries (I think I may have disabled major portions of the copy on write semantics of fork, actually). Booting the system, even in single user mode, failed in fairly obscure way (init said "No more processes at this runlevel" and just sat there). Of course booting with init=/bin/sash worked very nicely.

Your story just made me think about this, and I felt like 'sharing'. (Awww...)

Re:booting from pendrive

[tenman]

What happens if you have more than one bootable USB device? USB assigns ID's to devices dynamically, so that sda1=drive1 is not ALWAYS true. USB polls for devices, and then waits for the devices to respond. Device ID's are handed out "first come, first served" basis. While that's great for cameras, where there software looks for a device with a particular media type in it's QMS response, a bios will not have the luxury of obtaining a particular QMS signature (again where there is more than one bootable usb drive) before it begins the boot sequence. Not in today's BIOS anyway.

Re:booting from pendrive

[david.given]

I'm working on a run-from-CD system. To speed up testing, I'm doing the development by booting the kernel off CD and then using a USB disk for the root filesystem.

Setting it up's pretty easy; just tell Linux that the root is /dev/sda1, insert the mass storage driver into the kernel, etc. No initrd or user daemon is necessary.

However, the delay-before-detection bit me. USB seems to be initialised last, so by the time Linux tries to mount the root filesystem the USB bus is still powering up and Linux panics because it can't find the root. I fixed this by patching the kernel to have a 3s delay just before mounting the root filesystem. What I'd really like to do is to move the USB initialisation so that it occurs before the IDE initialisation; as detecting the IDE devices takes about three seconds anyway, that would give time for the USB stuff to come up without slowing down the boot process.

Re:booting from pendrive

[Anonymous Coward]

BTW, to the original poster: please write a nice HOWTO when you get it working. ;)

Re:booting from pendrive

[SEWilco]

A better solution would be to change the "mount the root filesystem" step to wait and retry if root is not available.

The dumb way is to use a sleep() with a maximum number of tries. The smart way is to keep trying until all drivers are done initializing (and drive access times out -- it can take a while in a configuration where the mount is initiated by a boot-time audio message through the speaker and someone has to insert a disk...), or at least all drivers which are relevant, which is pretty hard to determine due to so many possibilities, particularly if networking is involved.

Booting from USB drive

[SpatchMonkey]

Yes, it is a possibility, except that your BIOS would need to support:

1. Recognition of USB hard drive
2. Booting from said hard drive

It is the BIOS that needs this because it is the last code to be run before booting into an OS.

Re:Booting from USB drive

[dgmartin98]

Why would someone moderate this to "5: Informative" ??

SpatchMonkey's comments are:

1. In the article
2. Obvious

Re:Booting from USB drive

[Anonymous Coward]

Hey - it's only obvious if you know it already.

Re:Booting from USB drive

[Anonymous Coward]

wrong... It is obvious.

1) To boot from a device the BIOS must see it
2) The device must be bootable

what is NOT obvious about it? It would be more informative if it covered the compile options for the kernal to make the boot happen, or the sequence that one would have to run in order to make it work.
SpatchMonkey couldn't boot a USB drive if his life depended on it, if he thinks that is all there is to it.

Need a better bios for most pcs

[norwoodites]

Most PC have sh*t bios, they have no concept of booting from any device than the ide bus.

Intel and AMD should go out and implement an OF base bios then companies could make one card for ia32, ppc, and sparc base machines without writing different bios for the card, they would write in forth.

There is a project somewhere that is writing an open source base OF bios.

And how about Firewire?

[Anonymous Coward]

I also wish the BIOS manufacturers would get their heads out of the 80's and add firewire boot support. OHCI-compliant boot support would allow us to ditch IDE (and maybe even SCSI) for good. Anyone heard of such a thing?

Re:And how about Firewire?

[Anonymous Coward]

A mac maybe?
It can boot from Firewire and USB and even the net with standards, no s**ty pxe, just bootp/dhcp and tftp and nfs (or afp or any other network file system).

I think Sun also have this capitable.

Re:And how about Firewire?

[Anonymous Coward]

Geez... that last word was a train-wreck ;) Capability, maybe?

Re:And how about Firewire?

[Anonymous Coward]

There is no mainstream PC mainboard with a bios which supports booting firewire. There's a lot of complaining about this on usenet because it prevents people from using external firewire drives as backup devices. The Phoenix bios (which is often used in Laptops) supposedly can boot from firewire and both Linux and Windows XP have the capability to continue booting if the bios supported booting ieee1394 in the first place, but that doesn't help: Mainboards use Award or AMI BIOSes and firewire card makers prefer to bundle useless video editing software instead of putting a BIOS on their cards. Short: Firewire on PC sucks, get a Mac.

Re:And how about Firewire?

[Anonymous Coward]

It can boot from [...] the net with standards, no s**ty pxe, just bootp/dhcp and tftp

Bootp/dhcp and tftp are exactly what PXE uses. PXE is a framework for bootloaders. Macs obviously don't need such a framework as there is only one entity producing their bootloaders. The boot process after dhcp and tftp depends on the operating system.

Re:And how about Firewire?

[rakslice]

>>I think Sun also have this capitable.

Uh... I don't think so. Even in the fairly new Solaris 9, support for USB and 1394 hard drives is fairly sketchy.

Amptron

[theNote]

I just bought a new Amptron MOBO and the BIOS supports this.

The BIOS also has some network features built in, but I haven't checked them out yet.

Go try one out, they're pretty cheap.

Re:Amptron

[shepd]

>I just bought a new Amptron MOBO and the BIOS supports this.

Most likely they are lying to you.

PCChips and Amptron are virtually the same company. PCChips is the company that uses fake chipset names, fakes CPU speeds in BIOSes, fakes cache settings in BIOSes, uses plastic cache chips, and pirates BIOS code.

I wouldn't trust anything in a BIOS that's built for a PCChips board without a _lot_ of testing.

Oh, I can provide references to these little facts, too. :-)

Hmm

[Anonymous Coward]

Couldn't the person asking the question have pressed 'del' on boot, check to see if USB is deemed bootable by the bios?

What does the os have to do with the bios anyhoo?

Couldn't they have asked google about this?

Next ask slashdot, oh wait my dumb unresearched question has already been asked before, shucks did ziff davis by VA linux?

Re:Hmm

[Anonymous Coward]

What does the os have to do with the bios anyhoo?

The os needs to know how to take over from dos int13. That means the driver for usb has to be loaded and initialized before the os leaves BIOS/DOS world behind. For example, linux has both usb and firewire drivers, but it's not enough to load these drivers before the kernel mounts the root filesystem and starts init. You have to virtually "attach" the root device in a script from initrd. This is the step where other systems could run into trouble, too.

For Compact Flash...

[zoid.com]

You could try a acomact flash to IDE interface in order to boot from CF. I know alot of people are using this for IOpeners. http://www.acscontrol.com/Pages/Products/CompactFl ash/IDE_To_CF_Adapter.htm?=AdSelect

Cheers

USB not for harddrives

[jhunsake]

USB was designed for simple, low throughput devices. You should use firewire or external scsi.

Re:USB not for harddrives

[Anonymous Coward]

Very good point. I dont use linux though so I dont know how good the firewire support is. Does anybody know??

Re:USB not for harddrives

[Anonymous Coward]

Works fine though it should still be considered experimental. If you can get your bootloader to load the kernel and an initial ramdisk, you can even boot from firewire.

Re:USB not for harddrives

[AyeRoxor!]

"USB was designed for simple, low throughput devices."

Yeah, stick to ultra-fast devices like floppy drives.

Hmm...... :P

Mac OS X and USB/Firewire

[norwoodites]

On macs with os X, the OF reads from the devices and then the os sends messages to the of to read particular blocks from the device to get the driver and then loads the drive and lets the driver take over. In fact this is how they do scsi and ide. The OF(BIOS) contains generic drivers to load the kernel and also to read from the device.

Re:Mac OS X and USB/Firewire

[GrendelWraith]

OF = Open Firmware
This is also what allows my iBook to boot to Target disk mode. ie: the iBook becomes a firewire harddrive. Mountable on other Firewire equiped Macs.

What does OF stand for?

[Mustang Matt]

I know, stupid question, but I'm missing it.

Re:What does OF stand for?

[riggwelter]

OpenFirmware

It's sort of the Mac equivilent of a BIOS if you like

Re:What does OF stand for?

[Tsk]

Open Firmware.
Basicly it's a forth interpreter that initialises the processor, initialises various chips on the mother board and initialises PCI cards. It's avaiables on MacIntosh since the PPC switch and on sun Hardware.
Booting from a USB drive on a mac would not be difficult you'de just specify the path of the system blessed folder, be it a linux, Open, Net, Darwin or Mac OS X system.

Re:What does OF stand for?

[Anonymous Coward]

Actually it has not been available for Mac since the switch to PPC, it was the second generation PowerMacs that OpenFirmware came.
I have a PMac 7100 and it does not have OF.

Re:What does OF stand for?

[luphus]

Actually its available ever since the switch to PCI from Nubus, which happened slightly after the PPC switch. 61xx, 71xx, and 81xx (and possibly others?) are Nubus based and do not have Open Firmware. Not intending to be nitpicky :)

nwp

Good idea but...

[alpha264]

... this could be a security risk like the Dreamcast Phone Home project. Just stick a USB drive into the back of a computer where someone is away on vacation and turn the monitor off. That's probably even more "hidden in light" than a dreamcast, plus it would get past efforts to clamp down on such attacks that involve allowing only certain MAC addresses.

USB drives working with Sun Solaris?

[elwood_42]

Has anybody experience using these usb-stick with sun solaris on non-intel hardware? does it work?

You'd have to open the case

[yerricde]

USB was designed for simple, low throughput devices. You should use firewire

That defeats the purpose. Not all PC motherboards have integrated SCSI or FireWire controllers. (Most Macs have one or the other, but this article is about intel PCs.) By the time you've opened the case to install a 1394 or SCSI card, you could have re-arranged the ATA cables to boot from an ATA hard disk. The OP wanted a solution that worked without having to open the case.

Skip the USB

[Perdo]

Use a flash memory to IDE converter like this.

Then you realize flash memory costs more per MEG than hard drives per GIG and is SLOW.

Skip the fancy stuff unless you are just looking for toys.

Not exactly...

[Anonymous Coward]

Open Firmware is not in all PPC machines. It's in PCI and AGP Macs. I might be mistaken on this next part, but a Mac with Open Firmware can also be referred to as a NewWorld Mac (any non-beige Mac).

Boot USB? Hell I can't get lilo to boot CF!

[tzanger]

I have an IDE-CF bay, a PCMCIA-CF adaptor and a USB-CF adaptor. Now linux sees the CF in the USB adaptor as a scsi disk but the others are straight IDE.

I cannot for the life of me get lilo to correctly install on CF when in my laptop, and then boot in another computer. The CF reports itself as the same CHS whether it is in my PCMCIA slot or in the final computer's primary master CF-IDE bay. I've tried linear, lba32, with and without compact.

Example setup: install CF into PCMCIA adaptor, install adaptor into laptop. Laptop sees /dev/hde. mount /dev/hde1. /mnt/sbin/lilo -b /dev/hde -r /mnt. Lilo says it installs fine. umount, remove from laptop and place CF into CF-IDE adaptor on final computer. Boot. Disk is detected with same CHS as it was in the PCMCIA-CF adaptor but lilo will either say "LI" or "LI 0x01 0x01..." (0x07 is another common one.)

According to the LILO documentation that's illegal command and invalid initialization. Fun. Boot from a floppy on the target machine, run lilo from there, all is well. Unfortunately that isn't an option for me in all cases.

groups.google.com suggests that this is a longstanding problem with LILO (booting CF) but has no suggestions. Other than Grub which seems to be an excercise in bloat, has anyone got a solution to this?

Re:Boot USB? Hell I can't get lilo to boot CF!

[frooddude]

Use grub!!! I use my laptop to modify my firewall OS installation through a PCMCIA/CF adapter. (8MB card) and then a nice IDE to CF adapter in the firewall itself. Using grub it was *very* easy to get the bootloader installed on the CF card.

Boot from fd/cd, then mount the USB drive as / ?

[ishmalius]

This would be good enough, if it is possible.

This would be enough for me , as an alternative to booting directly from the USB. Does anyone know if this is easier, or even possible? It would -seem- to be easier, since the USB driver and fs could be modloaded instead of needing to be statically linked.

Anyone have any experience with this?

Re:Boot USB? Hell I can't get lilo to boot CF!

[tzanger]

Grub, eh? It looked like a huge time sink last time I looked at it, but perhaps it's time for a new look. :-) Thanks.

BTW have you ever tried to set the media write-lock on CF?

internal pcmcia reader

[kevinqtipreedy]

why not replace your floppy drive with an internal pcmcia or compact flash reader? it would only take up a 3.5 bay in your computer, and it would be recognized as an ide device. this would make botting from it much easier, even with an older bios. this may be a problem if you are using a laptop, but for desktops this would be your best bet.

Re:internal pcmcia reader

[Skuggan]

He was talking about *USB* drives!

With your sense of humor why don't tell him that he could replace the USB drive with a normal floppy drive or IDE disk...

Stupid, the matter som people are made of...

We already do this...

[Anonymous Coward]

Everyday almost. We image the machines and then also do fresh (boring long) installs from the 512MB Pen Drives. Your current mother board BIOS just needs to be recent (AKA no P2 or old systems). this way of fixing our machines has become quite useful and cheaper than burning cd's or trying to find the buggers.