Tollef Fog Heen's blog

tfheen Tue, 29 Jan 2013 - Abusing sbuild for fun and profit

Over the last couple of weeks, I have been working on getting binary packages for [Varnish] modules built. In the current version, you need to have a built, unpacked source tree to build a module against. This is being fixed in the next version, but until then, I needed to provide this in the build environment somehow.

RPMs were surprisingly easy, since our RPM build setup is much simpler and doesn't use mock/mach or other chroot-based tools. Just make a source RPM available and unpack + compile that.

Debian packages on the other hand, they were not easy to get going. My first problem was to just get the Varnish source package into the chroot. I ended up making a directory in /var/lib/sbuild/build which is exposed as /build once sbuild runs. The other hard part was getting Varnish itself built. sbuild exposes two hooks that could work: a pre-build hook and a chroot-setup hook. Neither worked: Pre-build is called before the chroot is set up, so we can't build Varnish. Chroot-setup is run before the build-dependencies are installed and it runs as the user invoking sbuild, so it can't install packages.

Sparc32 and similar architectures use the linux32 tool to set the personality before building packages. I ended up abusing this, so I set HOME to a temporary directory where I create a .sbuildrc which sets $build_env_cmnd to a script which in turns unpacks the Varnish source, builds it and then chains to dpkg-buildpackage. Of course, the build-dependencies for modules don't include all the build-dependencies for Varnish itself, so I have to extract those from the Varnish source package too.

No source available at this point, mostly because it's beyond ugly. I'll see if I can get it cleaned up.

[15:32] | tech | Abusing sbuild for fun and profit

Tollef Fog Heen <tfheen@err.no>