Hello I always use the command to kill the process kill -9 pid(process ID) . Today on my Red Hat 7.3 box accidently typed kill -9 -1 .. The monitor start blinking and everything freezed. My questions is : What is the purpose of these commands: kill -9 -1 kill -9 Thanks
First, I'd caution against casually using "kill -9". This is the harshest form of "kill" and cannot be stopped. It's almost always better to try one of the other signals (typically using just "kill" rather than "kill -9") in the first instance, and only use SIGKILL (9) if you can't shut the errant process doen more cleanly (see "man kill" for more details). Naturally, I don't want to try this on my system, but my guess is that the kill command parsed the -9 as the signal to send, then the following -1 as the process to kill. It may have stripped off the '-' and killed process 1. Process 1 is usually the "init" process which started all the other processes when the system booted up, and is a very bad thing to "kill".
Man page for kill sez -1 All processes with pid larger than 1 will be signaled. That includes just about everything. Wheee! Kerflump! Bzzzt! If you did this as root, it'd kill the works (a bad thing). If you were a normal user, I think it would only kill the processes you owned. Still not a good thing, but would leave the system intact. Try not to do that again