David Baron wrote:
Xen can run off disk images or real filesystems, in the sense of slicing off a partition using LVM and giving it as the virtual drive for the virtual host (domain). You can also have one domain that uses a disk image and another using a partition running on the same machine. Also you should be able to run a domain which has both a disk image and a partition. I'm not as versed with qemu although I've used it's basic functions using a disk image and having tried the same LVM partition slicing to see if it works.1. Is Xen mainly for sharing multiple operating systems running together, or are there some other really interesting uses?Xen is an advanced virtual machine. You can run one version of linux or such inside your installed version. Useful for testing the new version out, running things in a protected environment. I am no expert but I do not believe "sharing" is going on.Less advanced, easy to set up and use is qemu (using the kqemu accelerator kernel module).Both run off disk images, not real file systems.
The "official" packages for unstable or testing are usually going to have a problem being installed on stable due to library version differences. The backports being done at the same time as the testing/unstable packages are being released usually and attempt to take into account the version differences. There are also backport sites that can be installed via apt-get so you're not manually building and installing the packages needed. You may have to 'pin' packages to get all the dependencies working properly as it may require other packages besides the one you're trying to install.2. If you want to run Etch when it is stable, but need a package in Unstable is it better to. a.) Use "unofficially" supported backports? b.) Scrap stable and just go unstable? c.) Use Xen to run Unstable inside of stable?I am no expert. However, why not just install of "official" package from unstable. You can "test" first and see if it removes/replaces too much of your testing or stable installation. Backports will have similar effect but you have to manually build, install every piece.
Want to try unstable without going over to it. Use the virtual machine or a live-CD such as knoppix.