Here are my questions: is it possible to disable the fglrx Linux driver or do anything to suppress functionality (e.g. 3D acceleration) that is not cross-hardware compatible via a grub configuration? If so, how would this be done?
Specifically, I set up my preferred software dev environment on an SSD that I use in multiple machines, only some of which have discrete Radeon GPUs -- the others have Intel's iGPUs. On the machines with Radeon GPUs, gmd needs the fglrx drivers to run smoothly (3D acceleration is particularly janky without them). I need to be able to create/select boot options in grub that allow me to boot on an Intel device using the iGPU or an AMD device with Radeon GPUs.
All information I have found about modifying grub's boot menu is outdated, so I have turned to SU for clarification.
I have a dual boot set up on my PC: Windows 7 on one SSD and Ubuntu Gnome 14.04 on another (I use Ubuntu mostly for software development). I recently upgraded my PC from a couple of Radeon HD 7700s to an AMD R9 280, at which point the radeon drivers stopped working for 3D acceleration, causing everything to stutter. I then switched to fglrx, and all of the issues ceased. All was well in the electronic microcosm of my desktop.
The only issue is that I transfer this Ubuntu SSD from machine to machine as I hop between offices, houses, and cities. Not all machines have Radeon GPUs, which can cause issues with the fglrx drivers. Just today, for example, I went into an office and put my SSD in the computer I have been given there; it has an Intel CPU and has no discrete GPU. Grub would show my boot options as normal, but my attempts to start Ubuntu (even in "failsafe" graphics mode) would fail. I was fortunate enough to have a live USB stick with me, so booted the live distro, mounted/chrooted into the SSD, removed/purged fglrx, then rebooted.
This is not really an optimal solution. The ideal solution is to create a grub menu option to boot without fglrx-specific 3D acceleration.
Some More Specifics
root@toor:/$ grub-install --version grub-install (GRUB) 2.02~beta2-9ubuntu1.3 root@toor:/$ uname -orvp 3.16.0-50-generic #67~14.04.1-Ubuntu SMP Fri Oct 2 22:07:51 UTC 2015 x86_64 GNU/Linux
While the fglrx drivers are installed, booting on an Intel machine results in a rather annoying phenomenon: the screen will have green lettering saying something like "Starting web server apache...", which will then return constantly no matter what virtual terminal is selected. It took about 5 minutes to log in and
sudo reboot because the screen with green text kept taking over every 2-10 seconds (wildly varying and unpredictable timing). Hitting ctrl+alt+del would occasionally not cause the machine to reboot, or sometimes it would just lag for half a minute or so before responding. However, when it did respond, the gdm splash screen would very briefly appear before it rebooted.