Unable to mount root filesystem, kicks me into emergency shell

[stan]

On Wed, 26 Aug 2015 09:28:05 +0200
Scott van Looy <scott at ethosuk.net> wrote:

> Something happened recently in an update that’s rendered my system
> unbootable - am currently booted into an old (4.0.4) kernel after
> messing around with the boot parameters (specifically setting
> ROOT=/dev/sda7 and removing rhgb and other things).
> 
> Does anyone have any suggestions as to what it might be?

I don't have an answer for your question.  But I have a couple of
suggestions.

Run df to see which partitions are mounted where.
Use blkid to find the UUIDs of your partitions, and use those in the
fstab instead of labels.  It will also tell you if the LABEL you used
for root, /, corresponds to the UUID / partition that you think it
should. UUIDs are always unique, LABELs not so much.  I usually put the
labels as comments above the UUID line in the fstab file, for me, not
the system.

> ### BEGIN /etc/grub.d/10_linux ###
> menuentry 'Fedora (4.1.5-200.fc22.x86_64) 22 (Twenty Two)' --class
> fedora --class gnu-linux --class gnu --class os --unrestricted $
> menuentry_id_option
> 'gnulinux-simple-ad2acd30-8497-459c-9ba3-f250d7bea2aa' { load_video
> set gfxpayload=keep insmod gzio
> 	insmod part_msdos
> 	insmod ext2
> 	set root='hd0,msdos7'
> 	if [ x$feature_platform_search_hint = xy ]; then
> 	  search --no-floppy --fs-uuid --set=root
> --hint-bios=hd0,msdos7 --hint-efi=hd0,msdos7
> --hint-baremetal=ahci0,msdos7  ad2acd30-8497-459c-9ba3-f250d7bea2aa

This should be your boot partition UUID

> else search --no-floppy --fs-uuid --set=root
> ad2acd30-8497-459c-9ba3-f250d7bea2aa fi


The other thing to do is to rebuild the grub.cfg file.  First cp the
existing grub.cfg in /boot/grub2/ to something like grub.cfg.bak.  Then,
from the /boot/grub2/ directory, as root, run the command
grub2-mkconfig -o grub.cfg

That will scan your system and put sane results for any systems found
into the file grub.cfg.  You can then use diff to look at any
differences between the old config and the new config.  But the new
config should boot properly to any installed system.