No Title Bar button to close window Ubuntu 18.04

Since upgrading to Ubuntu 18.04 from Ubuntu 16.04, the titlebar buttons on the upper left corner of the window for closing, minimizing and maximizing windows have vanished.

Then I went to GNOME Tweaks (GUI menu) --> Windows --> Titlebar
and set the options to add maximize and minimize buttons to the title-bar. However there was no option for Window close button there:

Things I have tried to correct this

1. I installed gconf-editor and tried this gconf-editor solution
2. I did not understand the solution (if any) provided here

Output of the command

gsettings get org.gnome.desktop.wm.preferences button-layout

Output: 'minimize,maximize'

Solution 1:

Your window-control button layout doesn't look right. Run the following command in Terminal to reset it

gsettings reset org.gnome.desktop.wm.preferences button-layout

This should fix the problem. If it doesn't work, then set a suitable button layout manually. For example run the following command

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

to get the minimize, maximize, close buttons (in this order) at the right end of the title-bar.

Alternatively to get the close, minimize, maximize buttons (in this order) at the left end of the title-bar, run

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

and so on.

Solution 2:

Things have evolved since then. The solution will likely be a modification of the solution using gconf-editor you referred to. The key nowadays lives in a different place.

Install dconf-editor. Navigate to the key org.gnome.desktop.wm.preferences button-layout. Switch the "Use default value" toggle to "On". The value should become :appmenu,close. If your default would be different (since you upgraded rather than performing a fresh install), then manually enter the value :appmenu,close.