I am experiencing some strange problems in Ubuntu 17.10. At the login screen I am missing the small icon that allows changing between X and Wayland. In fact, the default installation is running X and not Wayland (verified by running echo $XDG_SESSION_TYPE in terminal, which outputs x11).
I also have duplicated processes running, for example two Xorg processes, two gnome-shell processes etc.., one from my user and the other from gdm user, which doubles the memory usage on startup. In order to see the duplicated processes I had to check "All Processes" in System Monitor so that it shows the processes of all users. Screen shots of System Monitor:
I did this because I found it strange that Ubuntu 17.10 was using 1.2 Gb ram at startup of 4 Gb total. Even Ubuntu 16.04 with Unity only used 800 Mb.
By exploring the virtual terminals with Ctrl+Alt+F1-7 I can see that there is always a gdm session at TTY1. My session is on TTY2. TTY7 outputs some kernel message like this "/dev/sda: clean files blocks", where in previous Ubuntu versions it was supposed to go back to my session.
This is a follow up of this Reddit post where I explain that the Ubuntu 17.10 install was a clean install and that I didn't install any Nvidia driver. Previously I was running Ubuntu 16.04.
Best Answer
I just encountered a similar issue to this (gdm3 was unable to launch wayland on my ubuntu 17.10 system) - I resolved it by switching to lightdm.
I was not seeing the duplicate process issues you report, but maybe that will help.