Booting Linux live CD from USB?

I'm using the Ultimate Boot CD, and I've added a bunch of customized .iso's to it. I can boot into those .iso files fine, but most of them are mini-versions of Linux that are designed to run off of a CD. When they try to boot, they try to run off the CD (which obviously isn't there since they're on a USB drive) and then either freeze, or don't work in some other way.

Is there any way to edit the .iso files to tell them they're booting off of a USB drive? I'm assuming there'd be something somewhere in the boot configuration files to do this. Where would that be? I would think it'd be different for different ones, but are there some places that are standard for live CDs? What would I have to change?

EDIT: Just to make exactly what I'm asking clear...I know there's stuff all over the place on how to boot a .iso from USB. That's not the problem, I can already do that. What I'm wondering is how to make the OS stored in the .iso realize that it's booting from USB and not CD?

Mako

Posted 2011-09-04T02:53:48.290

Reputation: 71

There is no difference. The problem you are describing really can't be caused by booting from a Flash drive instead of a CD drive. (Both are/can be USB.) You have a faulty disk image. – CarlF – 2011-09-06T19:39:36.880

I think the problem is that the .iso's use syslinux (or isolinux) to boot, and I think those systems are designed to boot off of a CD. I think there are ways to edit them to boot off of USB, however I'm not exactly sure how to do that. So I'm thinking there are two ways to go about it...either edit each individual .iso file and configure isolinux to boot from USB (I'm not sure how to do that) OR somehow make the flash drive seen as a CD-ROM drive by the BIOS (I'm not sure how to do that either ;) lol – Mako – 2011-09-06T20:14:15.360

Really, that isn't the problem. Either you have corrupted disk images, or you used Unetbootin wrong. They work great for the enormous majority of people. It's also possible that your flash drive is defective or your computer doesn't boot properly from USB due to BIOS problems. – CarlF – 2011-09-06T20:32:10.667

The USB boots fine. I'm using syslinux from the UBCD to then boot into (just for example) AOSS (which also uses syslinux). So I'm going from one boot menu, into another menu, into the OS. The problem is after the OS tries to boot, it fails. I noticed that in "isolinux.cfg" inside the .iso it had "boot=cdrom" so I changed it to "boot=usb". (Found that on a forum somewhere.) But it still didn't work correctly. – Mako – 2011-09-06T20:42:40.960

Again, it works fine for every other Unetbootin user. Try a different bootable distro, e.g. Knoppix, Ubuntu. – CarlF – 2011-09-06T20:52:39.617

Well it's clearly hit or miss with which .iso files will work...ideally the USB flash drive would emulate a CD...then when Linux mounts something at /dev/sr0 or /dev/cdrom it would be talking about the USB drive. – Mako – 2011-09-06T22:20:04.157

Answers

UNetbootin can boot any live CD image off a USB stick. (I think it works by emulating a CD drive.)

Some other options are listed here.

If you wanted to include several bootable CDs on the same USB drive, see How can I keep multiple live/bootable ISO images on a single USB drive?.

Mechanical snail

Posted 2011-09-04T02:53:48.290

Reputation: 6 625

I tried UNetbootin...the problem is that the LiveCD's are trying to boot from a CD. I can boot them from a USB, but the actual OS thinks it's on a CD, and so it messes up, because it doesn't try to read from the USB. – Mako – 2011-09-06T17:11:01.280

But I thought the whole point of unetbootin is to solve that problem. Am I mistaken? – Mechanical snail – 2011-09-06T19:38:42.787

I guess so, cause it didn't work :/ Thanks for trying though! :) – Mako – 2011-09-06T20:14:36.263

I have previously tried similar things. Any live CD image can be easily booted from your USB. I have tried it using a Ubuntu flavor of Linux and worked successfully.

Follow these steps:

Download the ISO Image file or Copy (which ever applicable)
Insert the USB drive and I recommend putting all your previous data in one folder(note:this data will not be accessible once the Live CD using USB is running)
Download Universal USB Installer.
Select the specific ISO in the drop down box and also select the USB which you want to make bootable.
Click next and set your options.
USB drive is now bootable.
To boot select boot from USB in startup of computer.
Run the USB as LIVE CD or install Linux from it.

For more details kindly visit: Ubuntu Website. Go to Option 2 and select USB for details.

aibk01

Posted 2011-09-04T02:53:48.290

Reputation: 1 044

Well I read through again, well this might also help! http://www.ehow.com/how_7207900_make-usb-cd-rom.html

– aibk01 – 2011-09-06T17:26:42.783