Stuck at fsck "/dev/sda1: clean xxx/xxx files [...] " after upgrade to Ubuntu 16 from 14

You'll also run into this exact error if you run out of disk space as well. I was stuck at boot

Ctrl + Alt + F1 or F2 into tty2 login

df -h says /dev/sda1 is 100% used

I find the stuff I need to delete with this command

du -d1 -h /home/username | sort -h

For example, I deleted some folders like so

sudo rm -rf /home/username/Desktop/folder/*
sudo rm -rf /home/username/.cache/*
sudo rm -rf /home/username/.mozilla/*

reboot and now it boots up no problem now

I finally managed to fix my problem. It looks like it was caused by issues from PPA for Ubuntu toolchain. I downloaded (from tty terminal) the debian of package libstdc++6 for Xenial at http://packages.ubuntu.com/xenial/libstdc++6

In my case (amd64) I did the following (on tty, Cntrl + Alt + F1 on the "error" screen):

# wget http://security.ubuntu.com/ubuntu/pool/main/g/gcc-5/libstdc++6_5.4.0-6ubuntu1~16.04.4_amd64.deb
# dpkg -i libstdc++6_5.4.0-6ubuntu1~16.04.4_amd64.deb
# reboot

And voilà, that solved the problem :)

If you recently installed nvidia drivers, you might have disabled nouveau drivers. In my case I managed to fix this by removing every occurrence of nomodeset from /etc/default/grub file and then by executing sudo update-grub.

This was because nomodeset disables the use of any graphic driver. I disabled my nouveau drivers before installing nvidia ones.

Though this might not be the case with everyone.

You need to run the following commands to install Intel graphics card drivers:

add-apt-repository -y ppa:oibaf/graphics-drivers
apt update
apt install xserver-xorg-video-intel

After that, run the below command:

sudo apt-get install ubuntu-desktop

Then: reboot

From: How to install the newest xserver-xorg-video-intel on 18.04 Bionic?