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I tried the combination CTRL+ALT+L or L but it is not working. But if I select the menu item LockScreen from setting drop down it works.

Any thoughts on how to fix keyboard shortcut?


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you will find a fast workaround here "go to System Settings > Keyboard and on the "Shortcuts" tab, under "System", change the "Lock screen" keyboard shortcut from CTRL + ALT + L to something else, then under "Custom Shortcuts", click the "+" button to add a new custom shortcut, under "Name" enter "Xscreensaver" and under "Command" enter "/usr/bin/xscreensaver-command", then click "Apply"." – Marius Balaban Apr 28 '12 at 7:29
Thanks @Marius Balaban. That helped.I cleared the shortcut and re-entered the CTRL+ALT+L combination and it worked. I tried to put it as solution but can't do that due to less reputation. – CppLearner Apr 28 '12 at 7:39
In my instance it was because my notebook keyboard implements a numeric keypad if the Num Lock is on. So my [Ctrl]-[ALt]-L was really [Ctrl]-[Alt]-3. Once I hit the Num Lock again to turn it off [Ctrl]-[Alt]-L worked again. – Stephen Gornick May 10 '13 at 0:35
up vote 21 down vote accepted

In the top panel right corner choose System Settings to select Keyboard in the Hardware section, or type "key.." in the Dash then select Keyboard:

enter image description here

In the Shortcuts tab all key combinations are listed. You may change them there or add your own custom shortcut. To have the poweroff shortcut back add it with a custom shortcut for the following command:

gnome-session-quit --power-off

Note: to be able to add a custom shortcut we may have to clear an already existing shortcut if this uses the same keys.

The GNOME lock screen feature depends on the gnome-screensaver Install gnome-screensaver. In case you have removed it or did not install it in a custom environment you will have to install it first.

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I changed the combination to Super+L but it is not working. Any thoughts? – CppLearner Apr 28 '12 at 8:09
thanks for your edit. I changed the key to CTRL+ALT+G and that worked. But changing it to Super+L is still not working. On Windows I am used to Windows+L hence same would be helpful on Ubuntu. Thanks – CppLearner Apr 28 '12 at 8:20
FYI: These instructions work for CentOS 7 as well (and probably any other GNOME 3 install). Super+L works for me. I also set Super+R for "run", like Windows. – Jonathon Reinhart Jan 3 '15 at 3:53
Strange. It was already set to Ctrl+Alt+L. This was what I always used, but all of a sudden it stopped working. But after resetting the shortcut to Ctrl+Alt+L, it started working again. Why did this glitch occur in the first place? I did change switch keyboard layouts back and forth once; could this be the reason? – Ébe Isaac Jun 13 at 5:31

This seems to have been improved in 12.10.

If you go into System Settings > Keyboard > Shortcuts, System,

then left-click once on 'Lock screen',

the Ctrl+Alt+L on the right changes to 'New accelerator...[something]', at which point you can hold Super [Windows key] and press L.

The keyboard shortcut will then show as 'Super+L' and works immediately.

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For my debian based crunchbag Distro the Window_Logo_Key+L is the shortcut for locking the screen but you of course change it as mentioned above

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