Comment 26 for bug 1397321

It turns out to be problem on my side, though I don't know whether or how I caused it as I'm not aware I was ever digging in booting stuff. This is log of my today's dpkg install|purge actions:

18:32:19 install linux-image-3.18.0-031800rc7-generic:i386 <none> 3.18.0-031800rc7.201411302035

Here I wrote comment #19, that the newest kernel does not boot, but learned I installed only one pkg out of three.

Here I am making some space on a tight /boot partition:

19:34:34 purge linux-image-3.18.0-031800rc7-generic:i386 3.18.0-031800rc7.201411302035 <none>
19:35:34 purge linux-image-3.13.0-36-generic:i386 3.13.0-36.63 <none>
19:35:39 purge linux-image-3.13.0-37-generic:i386 3.13.0-37.64 <none>
19:36:40 purge linux-image-3.13.0-40-generic:i386 3.13.0-40.69 <none>

Fully installing kernels for bisection as Joseph asked + the newest one again:

19:37:32 install linux-image-3.13.11-03131105-generic:i386 <none> 3.13.11-03131105.201407181735
19:37:41 install linux-image-3.13.11-03131106-generic:i386 <none> 3.13.11-03131106.201408131735
19:37:51 install linux-image-3.13.11-03131107-generic:i386 <none> 3.13.11-03131107.201409181736
19:44:14 install linux-image-3.18.0-031800rc7-generic:i386 <none> 3.18.0-031800rc7.201411302035

Discovering not only NONE of them boot (all fall into initramfs prompt), but my fallback kernel 3.13.0-34 (that I didn't touch today) start to run into PANIC, blinking Caps LED, power off-on needed. Took a panic screenshot.

Able to boot in Recovery mode as always, I removed all tested kernels and installed the newest distro one again.

20:09:06 purge linux-image-3.13.11-03131105-generic:i386 3.13.11-03131105.201407181735 <none>
20:09:11 purge linux-image-3.13.11-03131106-generic:i386 3.13.11-03131106.201408131735 <none>
20:09:17 purge linux-image-3.13.11-03131107-generic:i386 3.13.11-03131107.201409181736 <none>
20:09:23 purge linux-image-3.18.0-031800rc7-generic:i386 3.18.0-031800rc7.201411302035 <none>
20:09:23 install linux-image-3.13.0-40-generic:i386 <none> 3.13.0-40.69

This leaves me with the panicking ver. -34 and (initramfs)-ing ver. -40.

Then I started to experiment as I thought possible errors might be hidden from me. So I picked -40 in GRUB screen, chose to edit commands and removed 'quiet' and 'splash' words from line:

linux /vmlinuz-3.13.0-40-generic root=/dev/mapper/xubuntu-root ro quiet splash $vt_handoff

I was quickly asked for the LUKS passphrase in text mode, then the system went up and all appears to work.

I have no idea what caused the problem. Luckily I have at least my system back. Attaching my /boot/grub/grub.cfg just for the record.

Sorry for unintentionally leading the thoughts the wrong way.