[systemd-devel] Integrating better with systemd

[Manuel Amador (Rudd-O)]

For a while now, I've been experiencing a few woes related to systemd, booting 
with ZFS on the root, underlied by dm-crypt, and my generator-based approach.

Here is the ideal situation I would like to have:

During initramfs:

- decrypt all available initial volumes (done by Fedora)
- import ZFS pools (done by our scripts)
- mount root file system (done by our scripts)

During early boot:

- discover all file systems mountable and schedule them for mount (done in my 
branch)
- perform late block storage initialization and decryption (done by Fedora)
- import any newly available ZFS pools (not done)
- schedule any new file systems available for mount (not done)

During  shut down:

- unmount everything (systemd does it)
- export pools cleanly (not done)
    because, if they are imported, the crypt FSes are never closed

The "not done" parts are really ticking me off.

It is supposedly possible that we can accomplish most of this stuff simply by 
using udev rules.  Udev rules could possibly announce "hey, I found a ZFS 
array component", and communicate to a userspace program that says "OK, this 
array is now ready to be assembled and imported, and it really belongs to this 
system, so import it now".  Or "hey I found a bunch of ZFS file systems after 
importing this array, and these file systems have a policy of mounting on 
import, so mount them in the right order now".

Of course, the question of "which file systems are essential for the system to 
boot up" is MUCH TRICKIER that way, because ZFS does not specify them on 
/etc/fstab.  So it might be worthwhile to keep my generator-based approach at 
least for early boot, and use the udev-based approach for pools that are made 
available later on during or after boot.

This would also give us hotplug and automount for free.

Can anyone give me more input and ideas?  I'd appreciate it a lot.  I'm 
crossposting to systemd-devel because I really have no idea, and this part is 
really not well documented.

Is anyone even using my branch of ZFS with systemd support?
-- 
    Manuel Amador (Rudd-O)
    http://rudd-o.com/