I've try to get Ubuntu on my IMac working, but get some trouble with graphic cards. I'm using an late 2009 iMac 27". Has an i5 CPU, 16G Ram and Radeon 4850.
Actual it's working with 'nomodeset' but I want got get GPU working. I've already found a solution but it's not working ( rEFInd & Linux kernel EFISTUB booting at Apple hardware, how to implement it? ).
I still get the 'No UMS Support' message on startup, done the following steps:
- Add additional flash disk to USB (won't damage MAC OS until Ubuntu works fine)
- Boot Ubuntu Mate 21.10 from USB stick (add 'nomodeset' on start to get screen working)
- Install Ubuntu Mate 21.10 on flash disk
- Attach 2nd monitor to display port and restart (external monitor is working fine at this point)
- Add 'nomodeset' to grub parameter and reboot
- Now I'm able to start ubuntu using internal display (pressing ALT on stat is still necessary)
- Install rEFInd
- Reboot, now I'm able to start ubuntu using rEFInd
- copy actual kernel to /boot/efi/EFI/ubuntu/vmlinuz
- add 2nd copy to /boot/efi/EFI/ubuntu/vmlinz.efi
- copy actual ramdisk to /boot/efi/EFI/ubuntu/initrd.img
- add entry to efi bootmanager using command " efibootmgr -c -d /dev/sda -p 1 -L "Ubuntu (efistub)" -l /EFI/ubuntu/vmlinuz.efi -u "root=UUID=1501fa7a-f266-4a92-908b-5f27f20d8cd1 rw initrd=/EFI/ubuntu/initrd.img quiet splash nomodeset" " (the UUID is my flash drive, first I used /dev/sdb1 but from time to time the flash disc is mounted at /dev/sdc1)
After reboot I still get the 'no UMS support' message. I've set the efistub entry in boot sequence at first place so I don't waste time during rEFInd startup. efibootmgr list 5s timeout, but I won't change this value actual.
I'm not sure if I missing some step, so if someone can give me hint what to try next I'll be happy.
