"no ums support in radeon module" error when booting to the Ubuntu 16.04.1 installer with nomodeset on 2011 MacBook Pro

Question

The only way of successfully booting past the GRUB menu was to use nomodeset on this old machine, but now I've gotten the error mentioned in the title. Does anyone know what else I can do to get this first boot to work?

Solution

BIOS provides VESA graphics support but this is low resolution. When an OS loads it switches to User-space Mode Setting to provide better graphics. (UMS) But 10 years ago it was decided that Kernel Mode Setting (KMS) was preferable to UMS. It took a lot of work to do but but all modern hardware (like Nvidia and AMD/ATI cards) now support ONLY KMS. An older machine can still do UMS but only with legacy drivers. I don't know if your macbook GPU has UMS or KMS (but I would guess it is KMS.) See this link: http://www.phoronix.com/scan.php?page=news_item&px=MTI2ODA

The Linux kernel got more aggressive and now does KMS for Grub (so that the splash screen can have high res graphics!) Sometimes this causes problems. Using the nomodeset boot option prevents loading of KMS until after Grub hands off control to the main kernel.

I have a newly built quality machine. It boots many different distros but won't do Ubuntu 16.04. I get the 'black screen'. I edited the boot options to eliminate all options EXCEPT ro and added nomodeset. (At a minimum, eliminate splash.) Now it boots fine. But I do see the "no UMS support in Radeon module warning" in my boot log. I think this is a bug in the kernel used by Grub. Try booting with only the ro and nomodeset boot option. (And, if that works, you will have to edit your grub file again after Ubuntu is installed to make the change permanent.)