Bug 219185

Created attachment 306763 [details]
Output of dmesg

Hi! I'm setting up a Linux machine for my daughter using a 2015 iMac that we have laying around.

So far, everything works great except from one problem: The system reboots when we try to shutdown or put it in sleep. Therefore, the only way to shut it down is to use the power button.

The machine is an iMac, 21.5-inch, Late 2015, model A1418.

Operating system: Linux Mint 22 Cinnamon

Since Linux Mint uses a kernel that is not suitable for bug reporting here, I installed kernel 6.10.6-061006-generic and the problem persists. 

I also previously tried current versions of Fedora, Ubuntu and Debian (which has kernel 6.1.27).

This seems to be a long standing issue also affecting other people as shown on this post that started on May 8, 2022: 

[Linux on iMac reboots instead of shutdown | Linux.org](https://www.linux.org/threads/linux-on-imac-reboots-instead-of-shutdown.40266/)

I tried to boot with passing acpi=off to the kernel in grub but that has the effect of hanging the machine when we try to shut it down. 

I verified that my kernel is not tainted: `cat /proc/sys/kernel/tainted` returns 0.

I attach the output of dmesg in case that's useful. 

I will be happy to provide further information and testing.

Thank you!