Looks like subj.
Have a KVM machine with jessie assembled via debootstrap. Fstab states
/dev/vda2 / ext4 rw 0 0
The partition labeled vda2 is listed in grub.cfg as the root partition
by its uuid.(via update-grub)
Added a disk to have swap on it. Booted normally, despite the fact, that
the new swap-disk was automatically labeled as vda and the disk with
root is as vdb:
# mount | grep ' / '
/dev/vdb2 on / type ext4 (rw,relatime,data=ordered)
So, systemd mounted root partition, whitout looking into fstab.
I don't have much experience in systemd, and now wonder how this "smart"
mount works.
Ivan Boro