These instructions are for Ubuntu 12.04 running the Unity desktop on which the lxde-core window manager was installed using either the Ubuntu Software Center or sudo apt-get on the command line.

The instructions may be the same for other versions of Ubuntu, but no guarantee is made.

When the Lxde Core window manager is installed in Ubuntu 12.04, it installs several packages and libraries it requires. Not all these packages and libraries are uninstalled when you uninstall Lxde Core. Several packages (like xscreensaver) do not get uninstalled.

If you are not sure if you installed lxde-core or lxde, I recommend following the uninstallation instructions on this page.

Even if you decide to opt for the quick uninstall method, at least you will know which flavour of Lxde was installed.

Of course, it doesn’t really matter much. If you uninstall lxde-core when you had installed lxde, then you end up leaving some files behind (but still fewer than if you had uninstalled the normal way). If you uninstall lxde when you had installed lxde-core, then everything will be removed – it is safe to remove / uninstall files that were never installed because they are simply ignored.

Quick Uninstall

This is not recommended because it will remove all packages normally installed with Lxde Core. This may include packages you previously installed (like xscreensaver) or were installed as necessary dependencies for other programs.

Note: this uninstall command assumes Lxde Core was installed on a fresh Ubuntu 12.04.

1) Open a terminal (instructions can be found here).

2) Enter the following command (it is very long and a single line):

sudo apt-get purge --auto-remove  libfm-data libfm-gtk-data libfm-gtk1 libfm1 libglade2-0 libid3tag0 libimlib2  libjpeg-progs libjpeg-turbo-progs libmenu-cache1 libobrender27 libobt0  lxde-common lxde-core lxmenu-data lxpanel lxsession lxshortcut obconf openbox  openbox-themes pcmanfm xscreensaver xscreensaver-data

It is easiest to copy the line and paste it into the terminal (right-click on the terminal and select Paste from the popup menu).

Preferred Uninstall

The better way to uninstall it is to follow the directions on this page.

This will show you on how to uninstall only the packages that were installed when Lxde Core was installed. The instructions are generic and work for any installed package.

It involves:

identifying which packages were installed and
creating a command to uninstall only those packages

It leaves intact any packages you may have installed (like xscreensaver) or that were installed as necessary dependencies for other programs instead of blindly assuming that they were installed along with Lxde Core.