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3. Running UML and logging in

3.1 Running UML

It runs on 2.2.15 or later, and all 2.4 and 2.6 kernels.

Booting UML is straightforward. Simply run 'linux': it will try to mount the file `root_fs' in the current directory. You do not need to run it as root. If your root filesystem is not named `root_fs', then you need to put a `ubd0=root_fs_whatever' switch on the linux command line.

You will need a filesystem to boot UML from. There are a number available for download from here . There are also several tools which can be used to generate UML-compatible filesystem images from media.

The kernel will boot up and present you with a login prompt.

Note: If the host is configured with a 2G/2G address space split rather than the usual 3G/1G split, then the packaged UML binaries will not run. They will immediately segfault. See UML on 2G/2G hosts for the scoop on running UML on your system.

3.2 Logging in

The prepackaged filesystems have a root account with password 'root' and a user account with password 'user'. The login banner will generally tell you how to log in. So, you log in and you will find yourself inside a little virtual machine. Our filesystems have a variety of commands and utilities installed (and it is fairly easy to add more), so you will have a lot of tools with which to poke around the system.

There are a couple of other ways to log in:

When you're done using it, run halt, and the kernel will bring itself down and the process will exit.

3.3 Examples

Here are some examples of UML in action:

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