La Salle Debain

Wondering what is going on with the port of Debian to the Minix 3 microkernal? Here's an update.

dpkg Ported

Well, the big news as I mentioned in my last post is that dpkg has been successfully ported. I haven't sent the patches to the maintainers just yet as they need review and clean up but I will do that ASAP. The architecture name is defined as minix_i386. (There is no k because I am using the Minix libc as well as the kernel.) I am currently targetting squeeze.

A Maze of Twisty Dependencies All Different

Armed with my new dpkg, I have begun building packages which has been an interesting experience. The Debian packaging systems greatest asset — dependencies — is also its most frustrating during initial bootstrapping. Take debhelper for instance; nowadays most packages depend on it and I personally wouldn't think of creating a .deb without it but it build-depends e.g. po4a which build-depends on...debhelper. Also some programs which are assumed to be present on linux such as ldconfig are simply not available on Minix. So currently theres a lot of dpkg --force-depends and even --force-all going on. Of course this is only a temporary problem until I get a full set of base packages built. The equivs package is coming in handy too. In lieu of working .debs, I have been using Minix native packages to fill in the gaps. They use NetBSD pkgsrc which is a new experience for me. I can't say I'm that impressed but they work and, being uptodate, are a good source of patches.

Works in Progress

The two big packages I need to work on next are perl 5.10.1 and gcc 4.4.5. I haven't touched the latter yet. Perl is failing in its second-stage bootstrap for reasons I haven't gotten to the bottom of just yet. I suspect it has more to do with deficiencies in my build environment than a problem in perl itself.

libc Deficiencies

As I mentioned last time, the situation has improved tremendously since Minix switched over to using the NetBSD libc but I am still running into problems with unimplemented APIs. Take getpwent(3) and getpwuid(3) for instance. Being able to map between user ids and names is kind of important you know? Even worse instead of being completely absent some of these exist as stubs. So they compile and link without warning but always return ENOFILE and so on. I was surprised to find that there is no standardized API for getting information on mounted filesystems. (Which e.g. df(1) needs.) Linux uses getmnt(3) similar but incompatible with System V. The BSDs use getmntinfo so probably this is what Minix will implement. GNU programs are good about portability but a lot of Free software is unfortunately Linux-centric. Hopefully the Debian FreeBSD port already has patches for these cases. There are several annoyances like this but I suppose I shouldn't complain too much. I am using an unreleased version of Minix which is under heavy development and I must say the upstream developers have been good about responding to my concerns.

Looking forward: fakeroot, grub2, ext2

fakeroot is a very handy development tool that frees a developer from having to create .debs as root. Alas it won't work under Minix as it depends on LD_PRELOAD and Minix doesn't even support shared libraries. fakeroot-ng sounds a bit more promising as it uses the ptrace(2) system call which is implemented in the Minix kernel though I don't know how well.

Minix is now multiboot compliant so it is possible to use grub2 instead of the Minix boot loader. Definitely something I'm going to look at soon.

Minix now supports ext2 (though not ext3 or ext4) in addition to its native file system. For compatability this should become the default in the Debian port. While the kernel support is part of the standard Minix system, the userland support (e2fsprogs) is not for some reason. So I'll have to see about porting that.

Can I Help the Porting Effort?

Sorry not yet. Though if you are determined I'll try and help you get set up. Hopefully in a month or less I will be able to distribute a pre-alpha version so I suggest waiting for that. I am definitely going to be looking for outside help.