Sandybridge/Ivybridge/Haswell boxes take upwards of 10 minutes to just GET TO THE BOOT LOADER now. When I want to get a box into single user, and not miss the loader prompt when using FreeBSD:
nextboot -o “-s” -k kernel
ZFS based systems will emit a terrifying warning of:
WARNING: loader(8) has only R/O support for ZFS
nextboot.conf will NOT be reset in case of kernel boot failure
Which means you need to pay attention if your system panics on restart.