When booting to the graphical desktop fails we sometimes are recommended to boot into a "root shell" or to boot in "recovery mode".
How do I do that?
for 12.04.3 LTS and later
During boot press and hold the left Shift key or any other key. This will bring up the Grub2 menu from where we can select "Advanced options for Ubuntu".
After that we will be able to select the kernel we wish to boot in "Recovery mode":
This will lead us to the advanced options. By selecting "Enable networking" we gain access to our network and the internet for upgrades or downloads, and we will also mount our hard drives in read/write mode in case we need to edit files.
After the network has loaded, and fielsystems were mounted we will be presented again with the menu, from where we can choose "Drop to a root shell propmpt":
Note that we are root in this shell. Hence no sudo is needed for administrative tasks. This also means we have full access to all files, and we may cause irreversible damage to our system if we made a mistake.
If we had not enabled read/write access with "Enable networking" the filesystem will be mounted read only, and we are unable to edit files.
From the root shell type
for 12.04.0 LTS or earlier
During the boot process of the computer we press and hold the left Shift key. This will bring up the Grub2 boot menu from where we can select "recovery mode" (usually the second boot entry).
This will lead to the Grub2 recovery menu:
"Drop to root shell prompt" gives you a command line root environment from where you can access your files as root (no
Choose "Resume normal boot" to proceed booting as usual.
Note: see this question for a solution when the Grub recovery menu does not load the shell.
This will work if your file system is intact. The question is "why would I want to be on the console at this boot level?" If for example: your fstab has wrong entries, because you followed one of those tutorials or you have just experimenting, you are major hosed. Ubuntu insists to load the wrong file system although there is a message saying to Press 'S' to skip etc. which does absolutely nothing. Try it, you could be sitting there and waiting for something to happen for day's. The dead keyboard maybe related to a USB keyboard, but this is a very far fetched guess. If the loader isn't catching on that there is an error, there is absolutely no way that you could fix it from the console, even though there is an option to drop to a root shell that has absolutely no privileges. Should be called "GUEST" shell instead. That's my two cents and thoughts. My Point: the recovery option with such a scenario is absolutely useless, get ready to wipe and re-install.....