Slackware systems often run hundreds or thousands of programs, each of which is refered to as a process. Managing these processes is an important part of system administration. So how exactly do we handle all of these seperate processes?

The first step in managing processes is figuring out what processes are currently running. The most popular and powerful tool for this is ps(1). Without any arguments, ps won't tell you much information. By default, it only tells you what processes are running in your currently active shell. If we want more information, we'll need to look deeper. darkstar:~$ ps PID TTY TIME CMD 12220 pts/4 00:00:00 bash 12236 pts/4 00:00:00 ps Here you can see what processes you are running in your currently active shell or terminal and only some information is included. The PID is the "Process ID"; every process is assigned a unique number. The TTY tells you what terminal device the process is attached to. Naturally, CMD is the command that was run. You might be a little confused by TIME though, since it seems to move so slowly. This isn't the amount of real time the process has been running, but rather the amount of CPU time the process has consumed. An idle process uses virtually no CPU time, so this value may not increase quickly. Viewing only our own processes isn't very much fun, so let's take a look at all the processes on the system with the -e argument. darkstar:~$ ps -e PID TTY TIME CMD 1 ? 00:00:00 init 2 ? 00:00:00 kthreadd 3 ? 00:00:00 migration/0 4 ? 00:00:00 ksoftirqd/0 7 ? 00:00:11 events/0 9 ? 00:00:01 work_on_cpu/0 11 ? 00:00:00 khelper 102 ? 00:00:02 kblockd/0 105 ? 00:01:19 kacpid 106 ? 00:00:01 kacpi_notify ... many more lines ommitted ... The above example uses the standard ps syntax, but much more information can be discovered if we use BSD syntax. In order to do so, we must use the aux argument. This is distinct from the -aux argument, but in most cases the two arguments are equivilant. This is a decades-old relic. For more information, see the man page for ps. darkstar:~$ ps aux USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1 0.0 0.0 3928 632 ? Ss Apr05 0:00 init [3] root 2 0.0 0.0 0 0 ? S< Apr05 0:00 [kthreadd] root 3 0.0 0.0 0 0 ? S< Apr05 0:00 [migration/0] root 4 0.0 0.0 0 0 ? S< Apr05 0:00 [ksoftirqd/0] root 7 0.0 0.0 0 0 ? S< Apr05 0:11 [events/0] root 9 0.0 0.0 0 0 ? S< Apr05 0:01 [work_on_cpu/0] root 11 0.0 0.0 0 0 ? S< Apr05 0:00 [khelper] ... many more lines ommitted .... As you can see, BSD syntax offers much more information, including what user controls the process and what percentage of RAM and CPU the process is consuming when ps is run. Finally, ps can also create a process tree. This shows you which processes have children processes. Ending the parent of a child process also ends the child. We do this with the -ejH argument. darkstar:~$ ps -ejH ... many lines ommitted ... 3660 3660 3660 tty1 00:00:00 bash 29947 29947 3660 tty1 00:00:00 startx 29963 29947 3660 tty1 00:00:00 xinit 29964 29964 29964 tty7 00:27:11 X 29972 29972 3660 tty1 00:00:00 sh 29977 29972 3660 tty1 00:00:05 xscreensaver 29988 29972 3660 tty1 00:00:04 xfce4-session 29997 29972 3660 tty1 00:00:16 xfwm4 29999 29972 3660 tty1 00:00:02 Thunar ... many more lines ommitted ... As you can see, ps is an incredibly powerful tool for determining not only what processes are currently active on your system, but also for learning lots of important information about them.

Managing processes isn't only about knowing which ones are running, but also about communicating with them to change their behavior. The most common way of managing a program is to terminate it. Thus, the tool for the job is named kill(1). Despite the name, kill doesn't actually terminate processes, but sends signals to them. The most common signal is a SIGTERM, which tells the process to finish up what it is doing and terminate. There are a variety of other signals that can be sent, but the three most common are SIGTERM, SIGHUP, and SIGKILL.