A few days ago I watched a Q/A session with Linus Torvalds at Debconf 14. One of the main complaint of Linus towards Linux distribution was the way that distribution ends up using different versions of libraries than what has been used during application development. And the fact that it’s next to impossible to support properly all Linux distributions at the same time due to this kind of differences.
And now I just discovered a new proposal of the systemd team that basically tries to address this: Revisiting how we put together Linux Systems.
They suggest to make extensive use of btrfs subvolumes to host multiple variants of the /usr tree (that is supposed to contain all the invariant system code/data) that you could combine with multiple runtime/framework subvolumes thanks to filesytem namespaces and make available to individual applications.
This way of grouping libraries in “runtime subvolumes” reminds me a bit of the concepts of baserock (they are using git instead of btrfs) and while I was a bit dubious of all this (because it goes against quite a few of the principles of distribution integration) I’m beginning to believe that there’s room for both models to work together.
It would be nice if Debian could become the reference distribution that upstream developers are using to develop against Linux. This would in turn mean that when upstream distribution their application under this new form, they will provide (or reference) Debian-based subvolumes ready for use by users (even those who are not using Debian as their main OS). And those subvolumes would be managed by the Debian project (probably automatically built from our collection of .deb).
We’re still quite far from this goal but it will interesting to see this idea mature and become reality. There are plenty of challenges facing us.