Cannot boot system due to start job running for hold

I've installed ubuntu-desktop on Ubuntu 16.04 Gnome and I picked lightdm and now once I restart, I get this error message when I press CTRL + ALT + F2.

A start job is running for Hold until boot process finishes up (Xmin Xs/no limit)

This will last for twenty minutes What should i do to fix this problem or even troubleshoot it?

You can fix this in following way, it worked for me. FYI : I had upgraded from 14.04 to 16.04.

Go in your safe mode by hitting SHIFT key or ESC. select networking , then drop to root prompt. Then run following commands.

sudo apt-get remove plymouth
sudo apt-get remove xserver-xorg-video-intel

Now, reboot,

When you reboot, still you may get black or purple screen,

Press Ctrl+Alt+F1 and login with your username and password.

Then run the following commands

GDM ie Gnome display manager was also causing problems for me, so following step was essential for me

I switched to lightdm from gdm3 as display manager.

sudo apt-get install lightdm
sudo dpkg-reconfigure lightdm

When you are prompted, select default display manager as lightdm

Now I was back with desktop , without dash or unity but only icons and wallpaper. now run this.

sudo apt-get install ubuntu-desktop

Now, reboot after this.

The desktop is back

now, you can install intel graphic drivers again,

sudo apt-get install xserver-xorg-video-intel

Reboot now. Its done!