Package installs... If slim wont accept your password::

That is it simply keeps resetting to the login prompt.

Check system dbus is running::

 service dbus status     

(or whatever your using)

Check you have not slipped around a dependency which may happen if you have "extra" (non devuan repositories)

**  * cough*  *debian*   *ubuntu*  **

Certainly this could catch you if you use experimental or unstable (ceres) / you know that those names are no accident

 $ sudo apt-get update 
 $ apt-get install slim  --reinstall    

(optionally -t ascii or testing)

If slim is built with dbus you have to have dbus AND consolekit.

  $ apt-cache depends slim

     slim
    Depends: libc6
    Depends: libck-connector0
   Depends: libdbus-1-3
   Depends: libfontconfig1
   Depends: libfreetype6
   Depends: libgcc1
   Depends: libjpeg62-turbo
   Depends: libpam0g
   Depends: libpng12-0
   Depends: libstdc++6
   Depends: libx11-6
  Depends: libxext6
  Depends: libxft2
  Depends: libxmu6
  Depends: libxrandr2
  Depends: libxrender1
  Depends: zlib1g
  |    Depends: debconf
  Depends: <debconf-2.0>
    cdebconf
    debconf
   Depends: dbus
   Depends: consolekit
  Recommends: xterm
  Suggests: scrot
  Suggests: xauth