To test some more RTSP clients I’ve been working to get more virtual machines available in my system; to do so I first extended the space available in my system by connecting one more half-a-terabyte hard drive (removing the DVD burner from Yamato), and then started again working on a proper init script for KVM/Qemu (as Pavel already asked me before, and provided me with an example).
Speaking about it, if somebody were to send my way an USB or FireWire DVD burner I’d be probably quite happy; while I have other three DVD burners around – iMac, MacBook Pro and Compaq laptop – having one on Yamato from time to time came out useful; not necessary, so wasting a SATA port for it was not really a good idea after all, but still useful.
I started writing a simple script before leaving for my vacation and extended it a bit more yesterday. But in line with the usual virtualisation woes the results aren’t excessively positive:
- FreeBSD 8 pre-releases no longer seem to kernel panic when run in qemu (the last beta I tried did, the latest rc available does not); on the other hand it does seem to have problems with the default network (it works if started after boot but not at boot); it works fine with e1000;
- NetBSD still is a desperate case: with qemu (and VDE) no network seem to work; e1000 is not even recognised, while the others end up timing out, silently or not; this is without ACPI enabled, if I do enable ACPI, no network card seems to be detected; with KVM, it freezes, no matter with or without ACPI, during boot up;
- Pavel already suggested a method using socat and the monitor socket for qemu to shut down the VM cleanly; the shutdown request will cause the qemu or kvm instance to send the ACPI signal (if configured!) and then it would shut down cleanly… the problem is that the method requires socat, which is quite broken (even in the 2-beta branch).
Let me explain what the problem is with socat: its build system tries to identify the size of various POD types that are used by the code; to do so it uses some autoconf trickery, the -Werror switch and relies on pointer comparison to work with two POD types of the same size, even if different. Guess what? That’s no longer the case. A warning sign was already present: the code started failing some time ago when -Wall was added to the flags, so the ebuild strips it. Does that tell you something?
I looked into sanitizing the test; the proper solution would be to use run-test, rather than build-tests, for what I can see; but even if that’s possible, it’s quite intrusive and it breaks cross-compilation. So I went to look why the thing really needed to find the equivalents… and the result is that the code is definitely messy. It’s designed to work on pre-standard systems, and keep compatible with so many different operating systems that fixing the build system up is going to require quite a bit of code hacking as well.
It would be much easier if netcat supported handling of unix local sockets, but no implementation I have used seem to. My solution to this problem is to replace socat with something else; based on a scripting language, such as Perl so that’s as portable, and at the same time less prone to problems like those socat is facing now. I asked a few people to see if they can write up a replacement, hopefully this will bring us a decent replacement so we can kill that.
So if you’re interested in having a vm init script that works with Gentoo without having to deal with stuff like libvirt and so on, then you should probably find a way to coordinate all together and get a socat replacement done.