Cleaning some differences after upgrading UM 16.04 to 18.04


I recently upgraded my old Acer netbook (32 bits :cry:) from 16.04 to 18.04 and I found some differences in the boot process compared to a fresh 18.04 installation:

  • the grub2 theme: Ubuntu Mate 18.04 no longer uses a theme
  • an old lightdm greeter that can’t be configured from the Control Center

The grub theme issue can be solved deleting the folder /boot/grub/themes running:
sudo rm -r /boot/grub/themes

The lightdm greeter issue can be solved uninstalling lightdm-gtk-greeter packages:
sudo apt purge lightdm-gtk-greeter lightdm-gtk-greeter-settings ubuntu-mate-lightdm-theme

I also run sudo dpkg-reconfigure lightdm (just in case, but I think it’s not necessary).

Note that 18.04 uses slick-greeter.

To check that all the required packages are installed, run:
export LC_ALL=C; apt search lightdm | grep installed

you must get:

liblightdm-gobject-1-0/bionic,now 1.26.0-0ubuntu1 amd64 [installed]
lightdm/bionic,now 1.26.0-0ubuntu1 amd64 [installed]
lightdm-settings/bionic,bionic,now 1.1.4-0ubuntu1 all [installed]
slick-greeter/bionic,now 1.1.4-1 amd64 [installed]


The gnome-screensaver package was replaced by the mate-screensaver package but the update process does not remove it (this causes the screen to lock after suspension even when it is disabled).

This can be solved running:
sudo apt purge gnome-screensaver gnome-power-manager

Also reported here: