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I would like to create an OS-agnostic installation of Ubuntu on a flash drive, that boots under Ubuntu and under Mac OS X.

Ideally the process would look like:

  1. Install Ubuntu 11.10 (or 12.04 if necessary) on a flash drive (from Ubuntu).

  2. Boot from flash drive (on PC) to modify files, etc.

  3. Plug drive into Mac with OS X 10.4, boot to Ubuntu from it, and use.

I have an 8G flash drive. What is the sanest way to do this?

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What about, for example, grub? It seems grub would list the operating systems of the PC. Would the default entry (Ubuntu on flash drive) work on a Mac, unchanged? – thetester May 20 '12 at 16:13
Grub will only list OSs of the machine on which the full installation of Ubuntu was preformed, be it PC or MAC. Ubuntu installed on a flash drive should work on any supported hardware that can boot from USB. – mikewhatever May 20 '12 at 16:37

Because you have an 8GB flash drive, I'd recommend setting up a persistant live session, meaning when you boot your computer via USB you'll get an Ubuntu session that will retain your files and preferences (background image, theme, etc.). I've tried installing Ubuntu to a pendrive several times and it would normally crash beyond repair when running updates, yet running updates within a persistant live session seems to work well. On your Ubuntu box you should be able to access the Startup Disk Creator which will allow you to use an Ubuntu disc image and make your pendrive boot it. Ubuntu alone will take up less than a gig, you may want to grab the DVD edition which is 1.5 GB (includes GIMP so it's worth it), and you'll still have plenty of space for more software and files.

As for boot loaders, your pendrive will only boot Ubuntu, so not really an issue. Your non-Apple computers have a BIOS, where you have to make sure it's possible to boot from USB (Pentium 4's are a hit or miss, anything newer should be able to boot from USB). There are instructions here for booting Ubuntu via USB on a Mac. You may want to use UnetBootin on your Mac to make your pendrive bootable with Ubuntu.

If what you are looking for is like a portable virtual machine (which I doubt, because you said you want to modify files on your computer with USB running on a pendrive), it would be much more complicated for it to be OS-agnostic. Maybe using Qemu, but even then, you'd have to have it set up real well with emulators on the pen drive to be able to run a virtual machine on multiple computers/operating systems containing all the software to do that right on your pendrive.

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The Mac is a PowerPC, and holding the Option key at boot brings up the (Mac) OS menu, but it does not show the USB stick. Any ideas? Does it need an "Apple partition map" or similar as described here? – thetester May 26 '12 at 21:38
I think you would probrably need to format it in Ubuntu Disk Utility, and select GUID partition table, in order to boot on macs, although I am not sure whether these steps are required for a G4/G5(?) mac. For more help: – Marco Scannadinari Jul 15 '12 at 12:45
You might be out of luck for the PowerPC, unless you can hack the USB key to boot as if it were a CD... – titaniumtux Oct 11 '12 at 14:35

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