Prepares the system, terminates all processes, and then reboots the operating system. During preparation, all filesystem caches are flushed and running processes are sent a
SIGTERM followed by
Don't log the halt via syslog (i.e., mach_kernel, syncing disks, etc.).
Don't flush filesystem caches. Should not be used indiscriminately.
The filesystem caches are flushed but the system is otherwise halted ungracefully. Should not be used indiscriminately.