killall5 is the SystemV killall command. It sends a signal to all
processes except kernel threads and the processes in its own session, so it
won't kill the shell that is running the script it was called from. Its
primary (only) use is in the rc scripts found in the /etc/init.d
directory.
The program return zero if it killed processes. It return 2 if no process were
killed, and 1 if it was unable to find any processes (/proc/ is missing).