How to find the reason for the inability to load the server?

Question

ubuntu

ubuntu server 16.04.1 - became unavailable after reboot. I found out that it is loaded in emergency mode "Emergency mode". SSD disks - RAID - tried to check by booting into "Rescue" - fsck -y /dev/md127 - says that there are no errors on both disks. Where to look, what to look for? Help me please.
UPD
Checked /etc/fstab - there is some kind of nonsense

# <file system> <mount point>   <type>  <options>       <dump>  <pass>
proc            /proc           proc    noauto,nodev,noexec,nosuid 0       0
# / was on /dev/sda1 during installation
UUID=95f1c169-cdad-486e-a458-4df0be5d3dd4 /               ext4    noauto,errors=remount-ro 0       1
# swap was on /dev/sda5 during installation
UUID=2cb7074c-95d8-4c66-8e80-45824baee9ed none            swap    noauto,sw              0       0
/dev/fd0        /media/floppy0  auto    noauto,rw,user,exec,utf8 0       0
aufs / aufs rw 0 0
tmpfs /tmp tmpfs nosuid,nodev 0 0

Perhaps this is the reason? How to fix it?

Answer 1

The exact reason is not clear. As I can guess, RAID(5) crashed and there were errors on the second sdb disk
Errors were miraculously fixed, probably by fsck -y /dev/md2
Then I restored the RAID, first stopped all (0,1,2) multi devices mdadm --stop /dev/md0 ...
Then ran for luck mdadm --assemble --scan --force for good luck - it reassembled the RAID5 for me. Everything worked, but somehow dumb

~# more /proc/mdstat
Personalities : [raid1] [raid6] [raid5] [raid4] [linear] [multipath] [raid0] [raid10] 
md1 : active raid5 sdb2[1] sda2[0]
      39028736 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/2] [UU_]
      
md2 : active raid5 sdb3[1] sda3[0]
      460208128 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/2] [UU_]
      bitmap: 2/2 pages [8KB], 65536KB chunk

md0 : active raid1 sdb1[1] sda1[0]
      291520 blocks super 1.2 [3/2] [UU_]

[3/2] [UU_] - very similar to a bug. Support said that I have three disks sda, sdb, sdc, but in the raid I have only two disks, and the third one is for mirroring. I didn't understand what he meant...

Answer 2

Connect ip kvm and see what is displayed on the screen