How to fix "The system is running in low-graphics mode" error?

Will try to answer the ones I can:

Assuming the answer by Jokerdino was already checked: The greeter is invalid

Issues with Nvidia or AMD/ATI graphics

This happens when a driver has a problem installing correctly (Most cases). For this do the following:

1. Boot PC leaving SHIFT pressed to make the GRUB Menu show.

   

2. Select Recovery Mode which will continue booting correctly until the Recovery Menu appeares.

3. Select from the recovery menu failsafeX.

   

4. In some cases failsafeX will load fine (You lucky dog), for others (Me) it will give an error along the lines of "The system is running in low-graphics mode" and will stay there forever. When this happens, press CTRL+ALT+F1 to go to the terminal. Type in your Username and Password.

   

5. Reinstall the drivers depending on your case:

   • Nvidia

     sudo apt-get install nvidia-current - More stable/tested version sudo apt-get install nvidia-current-updates - More up-to-date version

     For other cases see this answer for details and follow the links there to help you along the way.

   • AMD/ATI

     The simple way is to sudo apt-get install fglrx. If this does not work keep reading.

     Go to AMDs support site and download the driver you need. (If you have a newer card, you may want to download be the latest beta driver instead of the stable one. You would need to compare release dates and read through release notes to find out which driver version supports which chips.) Put the downloaded driver in some folder and rename it to "amd-gpu.run" to simplify name. Go to the folder where you downloaded the file and type chmod +x amd-gpu.run to give it Executable Permission. Now just simply run ./sh amd-gpu.run and follow the onscreen steps.

     After rebooting all problems should be solved. If you test 'Additional Drivers' with a problem like this it will finish downloading the package but then it will give an error. It also gives the same error if you use 'Software Center' and 'Synaptic'. The only way was to go to the failsafeX option and do the workaround about changing to the tty1 terminal and doing it via command line.

Note that if the problem occured after installing an unsupported driver from the amd site then you may have to first delete the driver you had installed. For this, run in the tty session (i.e) in the terminal screen you get after pressing CTRL+ALT+F1 :

sudo aticonfig --uninstall

(If this command didnt work then check this site . Look under the "Uninstalling the AMD Catalyst™ Proprietary Driver" heading.) After doing this, you may reboot with the command :

sudo shutdown -r now

Now you must get back access to the Unity desktop(Of course with the AMD driver uninstalled). Then you can get to this site which clearly helps in choosing the right AMD driver for your System specifications. Also read the release notes for the latest driver for your graphic card(Especially check if your system satisfies all the system requirements). Then after downloading your driver installer(the .zip file) get to this site and follow the instructions to install your driver. Your driver must be installed and it should work successfully.

I also need to add that I do not recommend downloading the Drivers from the Nvidia site since they:

 * Might create additional problems with Ubuntu
 * Are not updated automatically
 * Are not tested thoroughly in Ubuntu

Always use the nvidia-current package or the nvidia-current-updates one. These are tested and approved already for the Ubuntu version you are using and will give less errors and incompatibility bugs.

Issues with Intel graphics

For Intel it is recommended to do the following after doing all the steps mentioned above but before installing anything (When you are in the Terminal). You can choose Xorg-Edgers which is a PPA that brings many improvements, latest video drivers and more:

Warning: This PPA is very unstable for some things. So do it with that in mind.
sudo add-apt-repository ppa:xorg-edgers/ppa -y

After that sudo apt-get update and you should receive several updates. X-Swat currently does not have Intel drivers in the latest versions of Ubuntu.

Update log

UPDATE 1: Added this extensive answer to solve many of the problems that might end with the error mentioned here: How do I install the Nvidia drivers?

UPDATE 2: AMD is no longer releasing (stable) graphics drivers on a monthly basis and not all graphics chips are supported by their Linux drivers upon product release. At the time of this update the latest stable driver is almost 5 months older than the latest beta driver. You should look at the release notes to check if there is a driver that supports your graphics chip and the software versions you are using (X.org xserver or Mir).

Like always please test and give feedback so I can enhance my answer since others will be also reading it. The better it is, the more people it will help.

I solved this problem by reinstalling ubuntu-desktop.

When the message that "your system is running in low-graphics mode" appears, press Ctrl+Alt+F1, then login with your credentials.

And then, run the following commands:

• sudo apt-get install --reinstall ubuntu-desktop
• sudo reboot

The greeter is invalid

This is a bug in LightDM and a bug report has already been filed.

The reason why you end up with this failsafe X is because the pantheon-greeter you installed along with the elementary desktop is now not available and LightDM is not able to identify an alternative greeter.

As a workaround, you can edit the LightDM conf file and correct the error.

Run the following command in a terminal:

sudo nano /etc/lightdm/lightdm.conf

and change the line

greeter-session=pantheon-greeter

to

greeter-session=unity-greeter

and save it.

After changing the file, reboot and you will now be greeted with Unity greeter.

You have too many files on your computer, and have exhausted disk space

Try moving personal files off the computer onto a USB drive.

To check whether this is the issue:

1. Press Ctrl + Alt + F1
2. Type df -h
3. If you see that there is no space available on the root (/) then you need to free some space.

To free space you can:

1. sudo apt-get autoclean
2. Look for large directories with sudo du -sc /*/* |sort -g and delete unwanted content,

3. Clean your home directory using a combination of

   cd ~   
   du -sc * |sort -g
   rm myLargeFile
   

When this is done, restart: shutdown -r now

When this happens there is often an error message indicating why it failed to start X.

Look in your /var/log/Xorg.0.log.old or /var/log/Xorg.0.log. The error (if there is one) will be at the tail end of the file. Another good place to look is the log files in /var/log/gdm/* (or /var/log/lightdm/* in oneiric and later).

Did you happen to manually install fglrx prior to noticing the problem? If it was not uninstalled properly it can cause weird random issues. Directions for purging fglrx are available at here.

Is your video card an AGP model? If so, a common issue with ati agp cards is having an incorrect AGPMode. Sometimes you can adjust this setting in your BIOS (which perhaps windows screwed with?) There is also a setting in /etc/X11/xorg.conf for adjusting it in X.

It is not related to Nvidia drivers. Because by default Ubuntu uses non-Nvidia drivers even though you might have Nvidia GPUs. I have an Nvidia GPU too.

My Ubuntu used to boot fine until something happened which caused the same issue. After reading posts, reading logs and little bit trial and error, turns out the problem is related to lightdm GUI server.

I don't know solution to the problem but there is a quick work around in 3 steps. This will save you from reinstalling Ubuntu.

1. When the error shows up, hit Ctrl+Alt+F1. This will open the command line interface. Login as root.

2. Remove a particular X11 config file. This file is not really required.

   rm /etc/X11/xorg.conf.failsafe
   

   Somehow, the existence of the above X11 configuration file causes the OS to throw that error.

3. Restart lightdm GUI server.

   service lightdm restart
   

This will restart the lightdm GUI server and voila your desktop is back!

Let's assume, arrogantly, that it is a problem with your X display manager.

Enter the terminal (you can use a virtual console if you cannot use a graphical terminal window), the one you said that you have access to, and enter the following:

sudo apt-get install gdm

. . . and choose gdm.

Then type:

sudo service gdm restart

(Or ... start instead of restart.)

According to https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1070150 this is a way to workaround a bug with lightdm.

Before typing that, you may need to first stop the other display manager that is running. This is usually LightDM:

sudo service lightdm stop

If you have trouble getting GDM to start, and this is an installed system rather than a live environment, then you can just reboot and it will start automatically because you configured it as the default display manager. (You should be able to shut down and restart normally. Otherwise, one way to reboot if the GUI is not working properly is to press Ctrl+Alt+Delete while on a virtual console.)

Only for ATI graphics cards

When the message that "your system is running in low-graphics mode" appears:
Press Ctrl+Alt+F1 to see the terminal one. Then login with your credentials, and then run the following commands:

sudo apt-get install fglrx    
sudo reboot

The same can be done from the recovery mode (after enabling networking), if your Ubuntu completly refuses to enter anything but recovery mode.

Follow these commands:

sudo apt-get update
sudo apt-get -d install --reinstall gdm
sudo apt-get remove --purge gdm

(I ran this command above, but was told by the system to use # sudo apt-get autoremove instead, after the #sudo apt-get remove --purge gdm command.)

sudo apt-get install gdm

select GDM when prompted

sudo reboot

That fixed it for me :)

It took very long to start after the reboot, 10+ mins. But I got in eventually.

I have recently received a similar issue with myPangolin Performance laptop. The folks at System 76 told me to do the following:

Click Okay and then select the option to get a terminal. (alternatively you can press ctr+alt+f1 to bring up another tty)

sudo chown lightdm:lightdm -R /var/lib/lightdm
sudo chown avahi-autoipd:avahi-autoipd -R /var/lib/avahi-autoipd
sudo chown colord:colord -R /var/lib/colord

reboot

These commands did the trick for me.