How do I reset Unity default shortcuts?

How do I reset the default value of Unity shortcut?

In: "System Settings -▸ Keyboard -▸ Shortcuts ..."

For instances:

• I can't put the default Alt L for the HUD.
• I can't put the default Alt+Print to capture the active window.

Simply typing it doesn't work.

Solving this in CLI is preferable.

Through GUI:

1. Install dconf-editor

   sudo apt-get install dconf-editor
   

2. Follow paths one by one, Click Set Default button on bottom right edge.

   /org/compiz/integrated/show-hud
   /org/gnome/settings-daemon/plugins/media-keys/window-screenshot
   

Using CLI:

dconf reset /org/compiz/integrated/show-hud
dconf reset /org/gnome/settings-daemon/plugins/media-keys/window-screenshot

References:

• man dconf
• A hint to get where any shortcut is stored, use dconf watch / Then try changing them from System Settings → Keyboard → Shortcuts

• Use -f option to reset a path or directory at once, example:

  dconf reset -f /org/gnome/settings-daemon/plugins/media-keys/
  

BTW, for HUD the default shortcut is Alt L, which is the Left Alt, not Alt+L.