I have been using uml (actually, pbuilder-uml) for a while to build my packages and ensure that the build dependencies were sane. Unfortunately, in sometime in the last month or so, something broke: now uml just hangs with the lines

Initializing stdio console driver
Netdevice 0

Since I have wanted to get back to playing with SELinux, and since Russel Coker has deprecated 2.4 based LSM patches ( kernel-patch-2.4-lsm), I decided to try to compile my own 2.6 based UML, especially since I heard tell on IRC that it was feasible to do so. Thats when the fun started.

Well, it started ok. Google quickly found the user mode linux home page, from where I down loaded the UML patches. People on IRC pointed me to updated host and skas patches for the 2.6.7 kernels. The patches applied, though with some fuzz.

There was some initial confusion (you really need to specify ARCH=um all over, even when configuring cleaning — took me a few minutes of confusion to figure that out). Then the kernel refused to compile. I tried all kinds of different host patches, but to no avail. Finally, I had to go on #uml for help, and I was told to turn off CONFIG_HIGH_MEM. That got the kernel compiled.

But then I kept getting the hangs while trying to get an initial network connection. Turns out that I had taken the dictates of the HOWTO too literally, which tell you to take the defaults. That is fine for 2.4 uml’s — for 2.6 uml’s, the defaults do not compile in anything. I compiled in all kinds of network methods.

Compile, run, and get a hang trying to get an initial console. Hmm. Go back and compile in input methods. Does not hang now — it just warns it can’t open an initial console (though it pops up xterms all over. This time it is the lack of a devfs that rootstrap needs. Compile in devfs.

And now things segfault in the UML since the libc is trying to get native posix threads library, not yet supported in UML. I tried all kinds of methods trying to set LD_ASSUME_KERNEL=2.4.17, but to no avail (Look at this thread on the uml devel list.)

I give up. Getting a 2.6.7 UML running is too hard, and I am certainly not a kernel compilation newbie. I gave a go to the 2.4.26 kernel based UML with the latest patches and all (still on a 2.6.7 host with SKAS3), and the uml does not even start. And the 2.4.26 UML would not have SELINUX in it, so my motivation is at an ebb. (or nadir, really).