Felix Miata wrote on Fri, 31 Mar 2017 02:22:10 -0400 <lots of helpful stuff, thanks>
>Your goal is to boot without Plymouth and without framebuffer, in >80x25 mode, to give Xorg the best possible chance to work as expect. >If Plymouth is installed, purge it. > >To proceed, hit the e key when the Grub menu appears, then remove any >line that says "load_video", and from any line that includes "video=" >or "vesa" or "vga=" or "quiet" or "splash", remove each whole such >string. Optionally, if the string "text" appears, remove it too. > >If all the above doesn't help, repeat it, but append "iomem=relaxed" to the >line >that included video and/or vesa and/or vga. OK, I did all that. More strictly I edited grub.cfg (I do have a rescue CD, so not a disaster if I broke grub.cfg) to comment out two calls of load_video, one in the menu entry for the boot and one in the preamble. The grub dialogue duly came up in 80x25 mode, encouragingly, but even with "iomem=relaxed" on the "linux" line I still had no joy when it came to starting X, alas. >Are you using a greeter, or logging in on a vtty and using startx or >equivalent? For this investigation I am using the latter, but normally I use lightdm and its greeter. I dispensed with lightdm here to simplify while trying to sort out what was going on. >What are the permissions on your /usr/bin/Xorg? -rwxr-xr-x >Doing something like 'journalctl -b -1 | grep -i failed' might be >useful. There is an awful lot of stuff making particular points of >interest hard to identify in the journal. It certainly is hard to find the needle in the haystack, even when as in my case much of it is gobbledegook. I've tried the suggestion but it didn't throw up anything very startling. One thing I have found is that although ctrl-alt-Fn has no observable effect when the xserver has jammed, ctrl-alt-del does provoke reboot, and the shutdown is reasonably orderly, as seen later in journalctl, so the underlying system is still flying. Thanks for all the other helpful instruction, even if it hasn't solved the problem. >It may be time for you to ask for help from the devs, using the >debian-devel mailing list or one of the freedesktop.org Xorg mailing >lists, or by filing a Debian bug. Yes, perhaps, if I can pluck up enough courage... Tony