Mint Display Manager (MDM) login problem

Tested on: Linux Mint 17.3 Rosa

Symptom: Cannot login to Mint Display Manager (MDM)

Login to a terminal by selecting CTRL - ALT - F1. OK then, it is not that you forgot your credentials.

Preparation:

It is essential that you carry out this to select the correct desktop.

aptitude search mint-meta

i   mint-meta-cinnamon          - Set of packages installed by default in the Cinnamon edition of Linux Mint
p   mint-meta-codecs            - All the packages required for multimedia support in Linux Mint
p   mint-meta-codecs:i386       - All the packages required for multimedia support in Linux Mint
p   mint-meta-codecs-kde        - All the packages installed by default in the KDE Edition of Linux Mint
p   mint-meta-codecs-kde:i386   - All the packages installed by default in the KDE Edition of Linux Mint
i   mint-meta-core              - Core Linux Mint packages
p   mint-meta-kde               - All the packages installed by default in the KDE Edition of Linux Mint
p   mint-meta-mate              - Set of packages required to run MATE
p   mint-meta-xfce              - Set of packages required to run Xfce       

There will be the letter i for installed beside mint-meta-core and a desktop like mint-meta-cinnamon, mint-meta-kde, mint-meta-mate or mint-meta-xfce corresponding to the Linux Mint Desktop types Cinnamon, KDE, MATE or XFCE.

IMPORTANT: only carry out the solution below for the installed desktop.

Solution:

sudo apt-get install --reinstall mint-meta-<desktop name>

or

sudo aptitude reinstall mint-meta-<desktop name>

where <desktop name> is: cinnamon || kde || mate || xfce corresponding to the i as determined in the preparation section above.