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This article mainly explains "What commands are used to manage processes on Linux", interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let Xiaobian take you to learn "What commands to use to manage processes on Linux"!

In Linux, every program and daemon is a "process." Most processes represent a running program. Other programs can spawn other processes, such as listening for certain events and responding to them. And each process requires a certain amount of memory and processing power. The more processes you run, the more memory and CPU cycles you need. On older computers (like my seven-year-old laptop) or lightweight computers (like the Raspberry Pi), you can get the most out of your system if you pay attention to processes running in the background.

You can use ps command to see what processes are running. You usually use ps arguments to display more output. I like to use the-e parameter to see each running process, and the-f parameter to get full details about each process. Here are some examples:

$ ps PID TTY TIME CMD 88000 pts/0 00:00:00 bash 88052 pts/0 00:00:00 ps 88053 pts/0 00:00:00 head$ ps -e | head PID TTY TIME CMD 1 ? 00:00:50 systemd 2 ? 00:00:00 kthreadd 3 ? 00:00:00 rcu_gp 4 ? 00:00:00 rcu_par_gp 6 ? 00:00:02 kworker/0:0H-events_highpri 9 ? 00:00:00 mm_percpu_wq 10 ? 00:00:01 ksoftirqd/0 11 ? 00:00:12 rcu_sched 12 ? 00:00:00 migration/0$ ps -ef | headUID PID PPID C STIME TTY TIME CMDroot 1 0 0 13:51 ? 00:00:50 /usr/lib/systemd/systemd --switched-root --system --deserialize 36root 2 0 0 13:51 ? 00:00:00 [kthreadd]root 3 2 0 13:51 ? 00:00:00 [rcu_gp]root 4 2 0 13:51 ? 00:00:00 [rcu_par_gp]root 6 2 0 13:51 ? 00:00:02 [kworker/0:0H-kblockd]root 9 2 0 13:51 ? 00:00:00 [mm_percpu_wq]root 10 2 0 13:51 ? 00:00:01 [ksoftirqd/0]root 11 2 0 13:51 ? 00:00:12 [rcu_sched]root 12 2 0 13:51 ? 00:00:00 [migration/0]

The last example shows the most detail. On each line, the UID (User ID) shows the owner of the process. PID (Process ID) represents the numeric ID of each process, while PPID (Parent Process ID) represents the numeric ID of its parent process. In any Unix system, processes are numbered from 1 and are the first process to run after the kernel starts. In this case, systemd is the first process that spawned kthread, which in turn created other processes, including rcu_gp, rcu_par_gp, and so on.

Use the kill command to manage processes

The system handles most background processes, so you don't need to worry about them. You only need to focus on the processes created by the apps you run. While many apps run only one process at a time (such as music players, terminal emulators, or games), others may create background processes. Some of these apps may still be running in the background after you quit, so they can be launched quickly the next time you use them.

When I run Chromium (the open source project on which Google Chrome is based), process management becomes a problem. Chromium worked very hard on my laptop and generated a lot of extra processes. Now I can open just five tabs and see these Chromium processes:

$ ps -ef | fgrep chromiumjhall 66221 [...] /usr/lib64/chromium-browser/chromium-browser [...] jhall 66230 [...] /usr/lib64/chromium-browser/chromium-browser [...] [...] jhall 66861 [...] /usr/lib64/chromium-browser/chromium-browser [...] jhall 67329 65132 0 15:45 pts/0 00:00:00 grep -F chromium

I've omitted a few lines where there are 20 Chromium processes and one grep process searching for the "chromium" character.

$ ps -ef | fgrep chromium | wc -l21

But after I quit Chromium, these processes were still running. How do I shut them down and reclaim the memory and CPU these processes consume?

The kill command allows you to terminate a process. In the simplest case, you tell the kill command to terminate the PID of the process you want to terminate. For example, to terminate these processes, I need to execute the kill command on all 20 Chromium process IDs. One method is to get Chromium's PID using the command line, while the other method runs kill against the list:

$ ps -ef | fgrep /usr/lib64/chromium-browser/chromium-browser | awk '{print $2}'662216623066239662576626266283662846628566324663376636066370663866640266503665396659566734668486686169702 $ ps -ef | fgrep /usr/lib64/chromium-browser/chromium-browser | awk '{print $2}' > /tmp/pids$ kill $(cat /tmp/pids)

The last two lines are key. The first command line generates a list of process IDs for Chromium browsers. The second command line runs the kill command against the list of process IDs.

Introducing the killall command

An easier way to kill multiple processes at once is to use the killall command. As you might guess from the name, killall will kill all processes matching that name. This means that we can use this command to stop all rogue Chromium processes. It's simple:

$ killall /usr/lib64/chromium-browser/chromium-browser

But be careful with killall. This command terminates all processes that match the name you give them. That's why I like to use ps -ef to check what process I'm running first, and then run killall for the exact path of the command to stop.

You can also use the-i or--interactive parameter to have killkill prompt you before stopping each process.

killall also supports using the-o or--older-than parameter to find processes older than a specific time. For example, if you find a malicious set of processes that have been running for several days, this will be helpful. Alternatively, you can look for processes that are older than a certain time, such as the runaway process you started recently. Use the-y or--young-than parameters to find these processes.

At this point, I believe that everyone has a deeper understanding of "what commands are used to manage processes on Linux", so let's actually operate it! Here is the website, more related content can enter the relevant channels for inquiry, pay attention to us, continue to learn!

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