I installed Debian Wheezy with the GNOME GUI, and then upgraded to Jessie using the terminal. After the upgrade was done, I tried logging out and logging back in, but it booted straight to command line view with no GUI. When I logged in and entered the startx command as root, all I got was a black screen. Do I need to manually update GNOME somehow, or is there another way to get to the GUI desktop? How do I change the boot parameters to boot to GUI by default?
You can check your runlevel (dictating whether you boot to console or gui) in /etc/inittab. A line like
id:2:initdefault: means you're set to boot to gui by default.
You might be having a X problem. Check your /var/log/Xorg.0.log specifically looking for lines with (EE) which would indicate problems to investigate.
I had the very same problem today while installing Debian Jessie via debootstrap.
The solution was: Xorg was apparently missing a .xinitrc configuration file in my homedir. Try the sample given in https://wiki.debian.org/Xinitrc
The most important lines are at the end of the file, where a windowmanager or DE is started via "exec"
Then again try "startx". Xorg should show up now without problems.