There are other users experiencing the same kernel panic issue when booting unraid on Mac Pro 4.1/5.1 or Mac Mini 2009. I'm hoping unraid team can help to identify and solve this problem.
In order to boot unraid on a Mac Pro, you must use the UEFI Boot with unraid. To isolate the issue, I have removed all the hard drives from the machine in later tests.
I used a capture card to get a clear output of the kernel panic screenshot attached. I've tried 6.8, 6.8-rc8, 6.8-rc9, they all showed the same kernel panic.
Kernel Panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) -6
My Mac Pro was able to boot 6.8-rc6/7, as it has a different kernel (5.7) and it gave a slightly different kernel panic output generally removed the register section. I've also tried different USB drives and different USB ports (Mac Pro only has USB 2.0), none of them worked.
Then I tried to append root=/dev/sda1. A little progress lead to a new kernel panic, now it has two error pieces:
devtmpfs: error mounting -2
Kernel panic - not syncing: No working init found. Try passing init= option to kernel.
Then I booted unraid in VirtualBox and verified that only /sbin/init exists, so I added init=/sbin/init to the kernel parameters. Then it showed a new kernel panic:
Kernel panic - not syncing: Requested init /sbin/init failed (error-2)
I don't feel confident with this error message, so I booted the USB drive in VirtualBox again and it started without a problem.
This is where I'm stuck, could anyone please point where I should go?