How to restore GRUB?

Stood on the railway since the release of Ubuntu 16.04, everything was good, every day sitting in it, in another day I run apt update && apt upgrade and went YouTube to watch and then after the abrupt shutdown (neighbors reptiles) are no longer loaded, the kernel panic was a "kernel panic not syncing vfs unable to mount root fs on unknown-block 0 0", in any mode and with any kernel, I decided Ubuntu Live to re-configure GRUB
Have remontiroval all that is necessary, I went through the chroot and executed update-grub showed that everything is OK.
Reboot and the first thing that alerted missing menu hornbeam, thought, well, okay. Then go download Ubuntu and have thought about fixed. But it was not there, the download was some pixel after the logo appeared and the lock screen is also blurred news and so on, trying to log into your account, enter the password and enter the lock screen disappears and then a second later again the lock screen and I rassohina, tried to log in under guest, still.

What to do not to reinstall Ubuntu again well it's all set up?
I understand completely copied the configs of GRUB and no boot options.

UPD#1
https://youtu.be/Wip8Y0SAVV4
June 10th 19 at 15:44
5 answers
June 10th 19 at 15:46
Solution
Grub is the boot loader.
If You loaded until you enter a password - the problem is not in grub.
I understand that if not logs, then there are 2 options:

1. Is not a valid username\password.
Deleted user? Or corrupted /etc/passwd file? (this is possible if HDD fell from Marika electricity)

2. The problem is lightdm (where you login is lightdm the default in Ubuntu) - can reinstall it?

I would recommend all the to save important files and reinstall everything from scratch, though it is not the linux way. Files still save better because I think part of the HDD died.
Updated the question and made the video, performed the second paragraph and it did not help. - Royal.Sauer56 commented on June 10th 19 at 15:49
press ctrl + f1
there will be a terminal.
Login through the terminal or not?

There is popping up a window at You about the system error, is it possible to click on "show more"?

Are there any logs in /var/syslog if log in from a bootable flash drive?

/etc/fstab file is not corrupted? - petra commented on June 10th 19 at 15:52
June 10th 19 at 15:48
Solution
1) Boot LiveCD c, to check the file system
2) to Reboot, switch to terminal (Ctrl+F1)
3) Log in the terminal
4) apt-get-f install
Did not help (( I updated the question and made the video what happens - Royal.Sauer56 commented on June 10th 19 at 15:51
June 10th 19 at 15:50
Solution
There is an assumption that there was an update of the grabb and during the update did not deliver the bits of the executable components of grub (and grub is configured by the set of scripts) and, accordingly, the next time grub-mkconfig (or whatever Ubuntu instead of) the old configuration is erased, and instead signed a new SNiP. Will have to boot from a live CD, to check that the disk in the first place - bucket, basic libraries, basic binari. If everything is in place, nothing proje... lost to pregenerate grub config again and pay attention to what it got in size - it's just a songwriter, you can view it.
In the evening check - Royal.Sauer56 commented on June 10th 19 at 15:53
June 10th 19 at 15:52
Solution
helped utility boot-repair on the live cd, don't know why but after it all booted fine, why update-grub didn't work I XS
grub, I think You fixed it, just boot to lightdm. - Royal.Sauer56 commented on June 10th 19 at 15:55
June 10th 19 at 15:54
Check out the available space.
Many more places - Royal.Sauer56 commented on June 10th 19 at 15:57

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