I recently tried booting into the Grub2's menu entry "Ubuntu GNU/Linux, with Linux 3.2.0-24-generic-pae (Recovery Mode) just to see what was there. It booted successfully, but I had no idea what to do after I was there. My question is where can I find some documentation on the recovery mode and what to do if I truly needed to be there. I'm running Ubuntu 12.04.
Ubuntu – How to boot into recovery mode
grub2
Related Solutions
The instruction Remove existing kernel options from the linux line and add single refers to changing the line
linux /boot/vmlinuz-3.5.0-26-generic root=<uuid> ro ipv6.disable=1 quirt splash $vt_handoff
to
linux /boot/vmlinuz-3.5.0-26-generic root=<uuid> single
which will boot up and show a text-mode terminal with root permissions ("single-user mode") from which fixes can be made.
The Ubuntu recovery mode is entered by setting linux options thusly:
linux /boot/vmlinuz-3.5.0-26-generic root=<uuid> ro recovery nomodeset
This provides a menu which automates some common system fixes, or lets you access a root shell as the single option would.
I know you posted this back in May, but I found some stuff that might help anyone looking at this article. I have the same exact problem, and I have not found a true fix for my symptoms yet, but I figured I would post some of my findings.
First, the trick with running some apt-get updates can be found here:link.
I modified mine a bit based on some other articles I read, and also because I encountered one error message with the cp command while trying to copy:
(This is assuming you did the first two steps from the link above and are running from a Live CD that you booted from)
sudo mkdir /media/precise
sudo mkdir /media/precise/proc /media/precise/dev /media/precise/etc
sudo mount /dev/sda1 /media/precise
sudo mount -o bind /proc /media/precise/proc
sudo mount -o bind /dev /media/precise/dev/
sudo mount -o bind /dev/pts /media/precise/dev/pts
sudo cp --remove-destination /etc/resolv.conf /media/precise/etc/resolv.conf
sudo chroot /media/precise apt-get update
sudo chroot /media/precise apt-get upgrade
sudo chroot /media/precise apt-get update --fix-missing
sudo chroot /media/precise dpkg --configure -a
sudo chroot /media/precise dpkg-reconfigure keyboard-configuration
sudo chroot /media/precise apt-get -f install
The reason I had to add the --remove-destination is because I was getting an error message that read something to the effect of:
cp: not writing through dangling symlink path/to/danling/symlink/a-file
(found the solution for that here: force cp to copy on dangling symlinks)
Secondly, it wasn't until the OS booted that the problem presented itself (hence why the Live Disk worked just fine). So, choosing different option in Grub was possible. I had gone back by two kernels and still had the problem.
Finally, while working on it with someone else at work, he had looked the computer the day before, and said that he booted back several kernels and got into command line, but not GUI. This was a great start because I had an Apache Web Server I needed to get up and available for people again ASAP. So, right now, the machine is running on an old kernel with a broken GUI but apparently working CLI and I am not sure what to do next. Try to remove the kernel? Remove and reinstall X? Not totally sure, but at least its a start, and maybe the link and code I listed above will be a fix for someone else with this problem.
Best Answer
The recovery mode is normally used when you need an exclusive admin access to your system. You normally go into the root shell and recover/repair the system through the command line.
Select the line which starts with "Advanced options". *
Select the line ending with "(recovery mode)", probably the second line, something like:
Press Return and your machine will begin the boot process.
After a few moments, your workstation should display a menu with a number of options. One of the options (you may need to scroll down to the bottom of the list) will be "Drop to root shell prompt". Press Return with this option highlighted.
The root partition is mounted read-only. To mount it read/write, enter the command
If you have /home, /boot, /tmp, or any other mount point on a separate partition, you can mount them with the command
(This must be done following step 8 so that
/etc/mtabis writable.) Alternatively, you could try to select "Enable networking" in step 7, though this has been found to cause the system to hang.* If you have Ubuntu Quantal (12.10) or earlier, omit step 4 (the recovery mode menu items are displayed on the top-level menu).
** If you reboot, there is no need to hold the Shift key in step 3. The GNU GRUB menu will continue to be displayed automatically on each boot until a normal startup of Ubuntu completes. To configure GRUB so the menu is always displayed, even after a normal startup, see https://help.ubuntu.com/community/Grub2/Setup.
Source: https://wiki.ubuntu.com/RecoveryMode