How to switch window controls to the left (Gnome Shell)?

For Ubuntu 12.04 and newer

You will need dconf-editor, which is part of the dconf-tools package. Install it first:

dconf-tools

Start dconf-editor:

Alt+F2 → dconf-editor

Go to org → gnome → shell → overrides → button layout. Change it to close,minimize,maximize:

No need to restart the shell.

Note: This also changes the cancel button in the overlay mode.

For 13.10 and higher

As per a few users, it may require a shell restart. Thank you all for pointing that out.

For 15.10 and higher

The schema is now org.gnome.desktop.wm.preferences as per this comment.

While technically not gnome-shell, if you're using gnome-flashback or gnome-flashback-no-effects the key is located at:

org -> gnome -> desktop -> wm -> preferences -> button-layout  

Changing it to:

close,minimize,maximize:  

should give you what you want.

You can use the command:

gsettings set  org.gnome.desktop.wm.preferences button-layout 'close,minimize,maximize:'

to get this done quicker.

For 10.10

The more simple way to do that is: Alt+F2 → gconf-editor

Navigate to apps → metacity → general, and double click on the entry: button_layout, then enter close,minimize,maximize:. You can also use spacer at some point to add a space.

For 11.04 and 11.10

Alt+F2 → gconf-editor

Navigate to desktop → gnome → shell → windows, and double click on the entry: button_layout, then enter close,minimize,maximize:. You can also use spacer at some point to add a space.