I just installed elementary OS on a iMac (27-inch, Mid 2011), with AMD Radeon HD 6770M. It generally works well, except one thing:

When I lock the screen super + L, or leave the screen and then come back and the screen is off and locked.

When I unlock everything is unresponsive, or at least very slow.
When I press a button it takes several seconds before I react.

Sometimes I can just go standby, and back and everything is back to normal. Sometimes I have to reboot to solve the problem.

2 Answers 2


Have you tried restarting lightdm?? When you get you screen locked, press CTRL + ALT + F1 and you will enter in console mode, then log in and execute the next command.

sudo service lightdm restart

if nothing happend then press again CTRL + ALT + F1 and check for an error message


Do you have any idea for permanent solution for this issue? Because restart of lightdm means closing all programsand that the system becomes unusable...

  • If you have 1 user with running session lightdm you can CTRL + ALT + F1 then login to user type killall light-locker then switch back CTRL + ALT + F7 (and start light-locker & again in terminal.
    – dmgl
    Mar 5, 2021 at 10:08

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