inicializando para GUI após uma mudança de unidade para gnome 3

Question

meu Ubuntu 16.04 estava rodando o Unity até que eu decidi recentemente mudar para o Gnome 3. Agora quando eu inicializo eu acabo no modo multi-usuário e tenho que logar no console e digitar starx para iniciar o GUI. Eu li vários posts sobre o assunto, mas estou intrigado com a minha configuração:

• eu tenho GRUB_CMDLINE_LINUX_DEFAULT="quiet splash radeon.dpm=1 radeon.modeset=1 i915.modeset=1" em /etc/default/grub
• também tenho env DEFAULT_RUNLEVEL=2 em /etc/init/rc-sysinit.conf
• Execução de systemctl get-default returns graphical.target

Lendo as postagens Espero que a última destas três informações de configuração seja a que é exercida no meu sistema, mas não parece ser o caso. Alguma idéia?

pós-edição para adicionar a saída de systemctl status display-manager.service :

 ● gdm.service - GNOME Display Manager  
    Loaded: loaded (/lib/systemd/system/gdm.service; static; vendor preset: enabled)  
   Drop-In: /lib/systemd/system/display-manager.service.d  
            └─xdiagnose.conf  
    Active: active (running) since mar. 2018-03-06 20:11:25 CET; 1 day 19h ago  
   Process: 2141 ExecStartPre=/usr/share/gdm/generate-config (code=exited,  status=0/SUCCESS)  
   Process: 2126 ExecStartPre=/bin/sh -c [ "$(cat /etc/X11/default-display- manager 2>/dev/null)" = "/usr/sbin/gdm3" ] (code=exited, status=0/SUCCESS)  
 Main PID: 2151 (gdm3)  
     Tasks: 3  
    Memory: 4.4M  
       CPU: 600ms  
    CGroup: /system.slice/gdm.service  
            └─2151 /usr/sbin/gdm3  
 mars 07 17:10:11 port-jct gdm-password][22146]: pam_succeed_if(gdm- password:auth): requirement "user ingroup nopasswdlogin" not met by user "cohen"  
 mars 07 18:44:44 port-jct gdm-password][26575]: pam_succeed_if(gdm-password:auth): requirement "user ingroup nopasswdlogin" not met by user  "cohen"  
 mars 07 19:39:53 port-jct gdm-password][29033]: pam_succeed_if(gdm-password:auth): requirement "user ingroup nopasswdlogin" not met by user "cohen"  
 mars 07 19:39:53 port-jct gdm-password][29033]: pam_unix(gdm-password:auth): conversation failed  
 mars 07 19:39:53 port-jct gdm-password][29033]: pam_unix(gdm-password:auth): auth could not identify password for [cohen]  
 mars 07 19:39:54 port-jct gdm-password][29038]: pam_succeed_if(gdm- password:auth): requirement "user ingroup nopasswdlogin" not met by user  "cohen"  
 mars 07 21:14:57 port-jct gdm-password][953]: pam_succeed_if(gdm-password:auth): requirement "user ingroup nopasswdlogin" not met by user "cohen"  
 mars 08 07:48:09 port-jct gdm-password][6299]: pam_succeed_if(gdm-password:auth): requirement "user ingroup nopasswdlogin" not met by user "cohen"  
 mars 08 08:50:11 port-jct gdm-password][9472]: pam_succeed_if(gdm-password:auth): requirement "user ingroup nopasswdlogin" not met by user "cohen"  
 mars 08 13:35:07 port-jct gdm-password][19396]: pam_succeed_if(gdm-password:auth): requirement "user ingroup nopasswdlogin" not met by user "cohen"