Well, I have a tall order. And apologies in advance if this has been covered before or I'm posting in the wrong place. I've looked long and hard for a solution to this without finding anything that seems satisfactory, and I can think of a number of categories this overlaps into.

I'm wondering if it's possible to install Linux to a USB drive such that you can plug it in and start using it without rebooting. Here are some of my criteria:

• Persistence: I want to be able to save data between sessions, and still store data on the drive.
  
• Bootable/Virtualizable: I would like to have the USB bootable, for use as a rescue CD, but also able to be virtualized, which I guess is still the correct term for what I talked about earlier (running it as soon as it's plugged in).
  
• Cross-platform: I would like for this to be able to run on essentially any arbitrary computer. Of course it will be limited by hardware, but I don't want it to be limited by, say, only working on Windows.
  
• Linux-based Install: Frustratingly, many things that look to me like they might do just what I'm wanting are Windows-based tools, such as LiLi & most things on PenDriveLinux. I don't have access to a copy of Windows (and I don't want to) outside of work, and I don't really have time to pursue this project at work.

I should probably also mention that I want this to basically work on a foreign or strange computer. I realize that I could make a bootable LiveCD USB in any number of ways and simply run it by using VirtualBox or some other emulation software. I want this to work on a computer that I haven't prepared in advance.

Something like portable qemu maybe? http://www.linuxquestions.org/questi...ml#post3969567

The reboot limit is the key problem and maybe admin. I use qemu all the time on locked down systems but and real virtual machine would be better. Someone made a portable virtualbox but it requires admin to run.

Other choices are bochs which is just like qemu.

User-mode linux and co-linux.

Thank you two for the quick and informative answers. Although I had discovered the Portable VirtualBox wrappers, I had not come across Portable Qemu, which sounds like it would do nicely for this application. Jefro, thanks especially for the multitude of options. I will look into these and perhaps implement one when I have more time.

For the record, I'm actually going to take a different approach, but I will document my solution here in case it helps someone else. (That's what LQ.org is about, after all.)

After realizing from the two answers I got that I'm not just missing something obvious, and that this is indeed a tall order, I sincerely rethought why it is I want this. Primarily, I want to be able to carry apps (esp. my password manager) around with me, as a matter of both convenience and to some extent security. Searching Google for something along these lines very quickly led me to PortableApp.com, which, though Windows based, is open-source and is said to run nicely under WINE. Thus far, on my new-ish Gentoo install with a barebones fvwm (no themes), I have found this to be true, so I'm assuming it would run nicely under anything. I have found no misbehaviors so far: it has been very cooperative, it's sleek, fast, and looks great.

So I've taken my 8GB flash drive that I meant to dedicate to this task and installed SysRescCD to it. Then I used parted to resize that partition (FAT32) to 2GB (since SysResc by default takes up the whole drive). I used the other 6GB to make another FAT32 partition which can house my portable apps. This way, I have a bootable rescue CD if I need it, and a cross-platform USB drive with some handy apps on it if I don't. If someone else finds themselves in this situation, I sincerely hope this helps.

Also, I'd like to give a nod to the LQ members. I'm reluctant to post on forums because so often I wait 3 days only to get what sounds like a rude answer from a nasty 14-year-old who didn't even read my post well. The answers I got here came quickly and were full of good information that I had not discovered on my own. In short, a perfect forum experience. Thanks to all who contributed.

John T. Haller and his assistants at portableapps.com did a great job on those. The apps performed well under a few odd situations and are close or exactly like the original apps.

Another place is portablefreeware but not all work like the portableapps do.