Bug#241472: gdm doesn't install /etc/init.d/gdm file :(
   
    Brian Sipos
     
    Brian Sipos <bjs5075@rit.edu>, 241472@bugs.debian.org
       
    Thu, 01 Apr 2004 18:09:16 -0500
    
    
  
You must first purge the GDM install. This means running the following command 
before reinstalling:
apt-get --purge remove gdm