[SOLVED] systemd on separate /usr with zfs root and /usr

[dscherger]

I've just finished the gnome 3.8 upgrade, which includes systemd and I'm having problems getting the init=/usr/lib/systemd/systemd kernel command line option to work.

I think the problem is that /usr is on a separate filesystem and isn't available at boot time. Both / and /usr are zfs filesystems and /usr/lib/systemd is NOT in my initramfs, generated by genkernel-next. The initramfs does contain the usr/lib/systemd directory and usr/lib/systemd/systemd-udevd executable but not the usr/lib/systmed/systemd executable used for init.

Is there an easy way to fix this?

I'm thinking about either including everything under /usr/lib/systemd in the initramfs (can I do that with genkernel??) or convincing zfs to mount /usr before init starts (assuming that's possible??). Other ideas/options/solutions are welcome!

The messages left on my screen after booting with the init=/usr/lib/systemd/systemd kernel command line option look like:

>> Initializing root device...
>> Detected zfs root: alpha/ROOT
>> Mounting alpha/ROOT as root...
>> Detected fstype: zfs_member
>> Using mount fstype: zfs
>> Using mount opts: -o rw,zfsutil
!! The filesystem alpha/ROOT, mounted at /newroot does not contain a valid init=/usr/lib/systemd/systemd
!! Please file a bug report with this message
Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000100

Booting without the init=/usr/lib/systemd/systemd option sort of works, although gnome doesn't get started (I get an "Oh no! Something has gone wrong" message displayed) and it appears the the old /sbin/init is running things rather than systemd.

Thanks

[dscherger]

Following up my own post with the solution that I ended up using:

The initramfs from genkernel-next actually does have provisions to mount /usr and other filesystems listed in /etc/initramfs.mounts
Appropriate ZFS entries for these additional mounts must exist in /etc/fstab for them to be mounted and I was missing these.

i.e. adding the following entry to /etc/fstab:
tank/usr /usr zfs defaults 0 0

Will cause the /usr entry in /etc/initramfs.mounts to be mounted by the initramfs before init (systemd) starts.

Not sure if this is also required but I have set the zfs mountpoint for /usr to be "legacy" as well.

Many thanks to jyxent on #zfsonlinux for the help.