Missing HDD spindown when halting recent Linux

Recent Linux kernel versions no longer spin down the disk by default when the system is halted. This behaviour appeared somewhere between the 5.8.3 and 6.10.5 kernel versions.

The reason is that several new sysfs variables were added in order to control disk spindown on system stop with better granularity. Unfortunately the defaults for these new variables lead to different behaviour when halting.

Note that only halting the system is affected (e.g. by doing /sbin/halt); powering off the system (by doing /sbin/poweroff) is not affected and does spin down the disk.

To restore the spindown-on-halt behaviour, set sysfs variables /sys/class/scsi_disk/*/manage_shutdown, /sys/class/scsi_disk/*/manage_system_start_stop and /sys/class/scsi_disk/*/manage_runtime_start_stop to 1.