# shutdown /?
/sbin/openrc-shutdown --single /?
 * openrc-shutdown: invalid time /?
Usage: openrc-shutdown -c | --cancel
   or: openrc-shutdown -R | --reexec
   or: openrc-shutdown -w | --write-only
   or: openrc-shutdown -H | --halt time
   or: openrc-shutdown -K | --kexec time
   or: openrc-shutdown -p | --poweroff time
   or: openrc-shutdown -r | --reboot time
   or: openrc-shutdown -s | --single time

Options: [ cdDfFHKpRrswChqVv ]
  -c, --cancel                      cancel a pending shutdown
  -d, --no-write                    do not write wtmp record
  -D, --dry-run                     print actions instead of executing them
  -H, --halt                        halt the system
  -K, --kexec                       reboot the system using kexec
  -p, --poweroff                    power off the system
  -R, --reexec                      re-execute init (use after upgrading)
  -r, --reboot                      reboot the system
  -s, --single                      single user mode
  -w, --write-only                  write wtmp boot record and exit
  -h, --help                        Display this help output
  -C, --nocolor                     Disable color output
  -V, --version                     Display software version
  -v, --verbose                     Run verbosely
  -q, --quiet                       Run quietly (repeat to suppress errors)


# shutdown -P 
The -P flag requires the -h flag