Strane UUID problem

[Heinz Diehl]

On 21.03.2015, Chris Murphy wrote: 

> I don't think systemd has any concept of filesystems (volume formats).
> It gets all of this from libblkid, udev, and the kernel. So I'd say
> one of those three things is confused, and then confuses everything
> else.

Didn't have much time today to further debug this thing, but I can confirm that
"something" is getting confused when rebooting for the first time with the new
partition.

Precisely: when I reformat /home with nilfs2 and check the assigned UUID
afterward, all is good. No /dev/sda with an erroneous UUID. Then I reboot, and
systemd claims it can't mount /home because "/dev/sda is busy". After dropping
into runlevel 1, lsblk shows why: now /dev/sda has the same UUID as /home, and
of course can't /dev/sda not be mounted.

So whatever it is in the system that can't handle a nilfs2 mount wrecks it
here. Will dig further into it, but it seems like it's systemd itself. I took a
look into the systemd source, and it uses common /bin/mount to mount the
filesystems. Manually mounting /home and going to runlevel 5 works flawlessly.
Something in the boot process is wrong.

> The fact you get a difference in output between lsblk and blkid is
> itself a bug.

I'm afraid it isn't, because blkid doesn't show the toplevel physical device,
while lsblk -f does. Anyway, that's obviously not the problem here. Something
claims /dev/sda has the same UUID as /home, and then systemd looks up the UUID,
grabs the first assigned device and tries to mount it. And I don't get why the f*ck
/dev/sda should have a UUID or what wrecks it..