After spending the past hour troubleshooting a "Welcome to emergency mode" problem on my system, whereby after a quick recovery mode test to see if I had finally got it working I couldn't boot anything but emergency mode, I figured I should post this in case it helps someone out in the future.
If you use systemd, have a partition mounted via fstab, and change that partition (whether it be splitting it, formatting to a different FS or whatever - anything that will change the way the drive presents itself to the system), be sure to change your fstab entry before you reboot. If you don't, systemd will choke and drop you to emergency mode at boot without so much as a bye or leave, and nothing to tell you why.
In my case, I'd reformatted an ext4 partition on my SSD to NTFS while testing efficiency to see if I could carry some benefits across to Windows on those rare occasions that I actually boot Windows, but I'd forgotton to change the fstab entry, and since I hadn't rebooted my system for three days, I'd forgotten I made the change. Oddly, my fstab and grub entries got themselves re-written to boot from and mount the platter drive rather than the SSD, too (adding to the confusion for me). I presume it picked the entries up from the platter drive, though how they got written back to the ssd I have no idea.
Even more annoying, systemd reported an error on one drive, though the one it complained about is not mounted at boot and is a truecrypt partition anyway. It didn't stop me trying all sorts of things (including adding it to fstab with "nofail") trying to get it working. The fix in the end was to comment out the entry for the changed partition and then it booted like nothing had happened. That hasn't stopped me missing my mid-week pint while I fixed it, though
I hope this saves someone else the headache.
Nvidia GTX 680 4Gb, AMD Phenom II X4 (965BE) @ 3.6 Ghz (Overclocked) 8GB RAM
Linux user #545703
I had a very similar issue, just today.
Thanks! Thanks! Thanks! Solved my issues after a fresh installation.