Comment 2 for bug 1153224

I've been trying to understand what might be required to do this. I don't want to make any decision on my own, so here's my probably incomplete outline. Most of the information was gleaned from reading the bugs/BP and discussing a bit with pitti. Errors are no doubt mine.

  - Update systemd to 195
    + Brings with it a udev SONAME bump

  - libudev1 transition. This can be done as a "soft" transition - the ABI hardly changed between the two (the on-disk format also didn't change) and so it's safe to have libudev0 (src:udev) and libudev1 (src:systemd) around simultaneously. There might be tweaks required to adjust for e.g. removed symbols (udev_get_{dev,sys,run}_path for example are gone and should be hardcoded).

  - Seed libpam-systemd and unseed libpam-xdg-support

  - Port packages as we can to using logind instead of consolekit. Both can coexist so this is another soft transition.

  - An outstanding question is what to do with the cgroups. Some software uses [ -e /sys/fs/cgroup/system/ ] or similar to mean either "Is systemd init?" or "Can I use logind?".