Strane UUID problem

[Heinz Diehl]

On 21.03.2015, Chris Murphy wrote: 

> OK it's a little annoying when you provide so little information from
> the very start about what you're trying to do, and what the setup is,

Here's what lsblk says before formatting:

AME   FSTYPE LABEL UUID                                 MOUNTPOINT
sda                                                      
├─sda1 ext4         6cb0a099-3037-4b82-87ad-e4058dc8944c /boot
├─sda2 xfs          5a16b831-b896-437c-8b8c-95d600ce90e0 /
├─sda3 swap         3f579e51-577f-4f8b-975c-d58aa3063f7e [SWAP]
└─sda4 xfs          1dc70566-e597-4c1a-baa8-c652b79c2010 /home
sr0

And here afterwards:

AME   FSTYPE LABEL UUID                                 MOUNTPOINT
sda    nilfs2       190d8a5e-81c3-461a-8602-1d67a01b59f3                                     
├─sda1 ext4         6cb0a099-3037-4b82-87ad-e4058dc8944c /boot
├─sda2 xfs          5a16b831-b896-437c-8b8c-95d600ce90e0 /
├─sda3 swap         3f579e51-577f-4f8b-975c-d58aa3063f7e [SWAP]
└─sda4 nilfs2       190d8a5e-81c3-461a-8602-1d67a01b59f3 /home
sr0                                                      

And this is systemd complaining that it can't mount /dev/sda:

[....]
Mar 20 17:11:27 ayna systemd: Mounting /home...
Mar 20 17:11:27 ayna kernel: Bluetooth: SCO socket layer initialized
Mar 20 17:11:28 ayna kernel: usbcore: registered new interface driver btusb
Mar 20 17:11:28 ayna kernel: NILFS version 2 loaded
Mar 20 17:11:28 ayna systemd: home.mount mount process exited, code=exited status=32
Mar 20 17:11:28 ayna mount: mount.nilfs2: Error while mounting /dev/sda on /home: Device or resource busy
Mar 20 17:11:28 ayna systemd: Failed to mount /home.
Mar 20 17:11:28 ayna systemd: Dependency failed for Local File Systems.
Mar 20 17:11:28 ayna systemd: 
Mar 20 17:11:28 ayna systemd: Triggering OnFailure= dependencies of local-fs.target.
Mar 20 17:11:28 ayna systemd: Unit home.mount entered failed state.
[....]

I do nothing more than booting into rl 1, formatting /home with nilfs2, set up
the correct UUID in fstab, and so reboot. Formatting /home with ext4 or xfs
works as expected, the UUID assigned to /dev/sda vanishes.