Subtitles of the Movie

In this video we look at controlling and monitoring processes. When you run the ps command from a regular console you don't see much, just a couple of processes, bash shell and the ps command itself. Now try something different ps aux, whoa, just about every process currently running on your system. Look at some of these columns, the column on the left is the owner of the process, the second column cites the process identifier often referred to by its acronym PID. The column with the S's means the process is currently sleeping. But don't worry about that if you're currently running the Apache web server for example you'll see that sleeping. But you can beat that will go into life if someone requests a webpage from you. Naturally the process you just ran is running or at least as running at the moment you ran that process. Specifically the ps aux command. Now let's take a second view, look at the top command, a lot of this should look familiar. You have the process identifier, the user who owns the process and the command question. There's more useful information here to. You have the CPU being used by a process as well as the percentage of memory being used by a process. If a process ever gets stuck you may see it taking high percentages of your CPU and RAM memory. And there's more information available from top. This is your currently available RAM memory in this case 512 mb. Most of it is currently being used, a little bit is free and there's a listing for swap space. There's about a gig of swap space none of it is used. So all of it is still free. What happens when a process gets stuck? It usually is using a lot of CPU and or RAM memory in that case you may want to kill it. For example if you've identified a problem with process number 1111 you can kill the process. 1111 is the pid and that command should kill the process, but it doesn't in this case because there is no process with that PID on my system. But let's do something else, I started a ping command and I go to another console and I want to kill that process. The process identifier is 2820, so let's see what happens when I run kill 2820. I go back to the other console and see that process has been terminated. Sometimes stronger measures are required. If the process wasn't killed you might have to run a command like kill 9 2820. This shuts down the process uncleanly which made leave some RAM unusable at least until the next time you reboot your system. But on most Linux systems that's a small price to pay to keep your system running for your users. Thank you and on to the next video.