Note: This is an attempt to create a canonical question that covers all instances of "low-graphics mode" error that occurs to a user, including but not limited to installation of wrong drivers, incorrect or invalid lightdm greeters, low disk space, incorrect installation of graphics card like ATI and Nvidia, incorrect configuration of xorg.conf file while setting up multiple monitors among others.
![How to fix "The system is running in low-graphics mode" error?](https://cdn-ak-scissors.b.st-hatena.com/image/square/664a2d3dc991972667a15e0e849615b9670c436b/height=288;version=1;width=512/https%3A%2F%2Fcdn.sstatic.net%2FSites%2Faskubuntu%2FImg%2Fapple-touch-icon%402.png%3Fv%3Dc492c9229955)