![]() They have a numeric value of 15 and 9 respectively. Although there are many different types of signals, we mostly deal with the “SIGTERM” and “SIGKILL” signals. ![]() In Linux, when a process is killed, a “terminating signal” is delivered to the process. You can either add sudo before any command to run it as root, or obtain a root shell by typing su, and then execute the command. However, a root user can kill all processes. With ps aux, the first column contains the username. In the case of top, the second column contains the username. Both top and ps show the user under which a process is running. If you are a normal user, you can kill your own processes, but not those that belong to other users. Now that we have located the process, it is time to kill it. However, before we learn how to do so, there are a few things you need to know. ![]() The output of top and ps contain additional information that help you determine if you can really kill a process. As we shall see in the next section, there are some circumstances in which you can’t kill a process. The pidof and pkill commands give you far less information. For our system, notice that we get all the PIDs that belonged to “nginx” in the above screenshot. This will match processes with the exact name of “nginx”, as well as any other process that matches the same criteria. As an example, to search for all processes that contain “ngin” somewhere in their name, run: pgrep ngin If you don’t know the full name, you can use pgrep instead of pidof. If there are none, you will get nothing as the output. If there are processes with the exact name of “nginx”, you will get a list of PIDs, as shown below. To get the PIDs of a process with the exact name of “nginx”, use: pidof nginx On the other hand, if you know the exact name of a process, you can use pidof to find its PID. The top and ps/ grep combination allows us to search for processes. So, even though we got a result, there are no processes that are of interest to us. Thus, even when there are no “vnstat” related processes running, we would get one entry showing the grep process: Since we were searching for all instances of the term “vnstat”, and we were also running grep with “vnstat” as its argument, we got grep as well in the results. Here, we got two results - the vnstatd process, as well as the grep process. For example, to find a process associated with the term “vnstat”, you can use: ps aux | grep -i vnstat The advantage of using ps is that you can easily filter this list with the grep command. The PID is available in second column from the left, and the process name is available on the rightmost column. The output of the command is similar to that of top. (Without this, ps won’t show processes running in a GUI environment.) u: Display the user who is using the process.In the above command, we have used the flags aux which have the following meanings: Locating the process with ps and grep commandsĪnother way to get a list of process is by running: ps aux As an example, in the above screenshot we have the vnstatd process running with a process ID of 263. The leftmost column contains the PID of the process, and the right side contains the program name. Additionally, the top command also has ways to filter processes by CPU usage, user and process names, which you can read about in this guide. To browse through this list, you can use the up/down keys. You can browse through this list to find the name or the PID of the process you want to kill. You will get an interactive interface, as shown below. Locating the process with the top command On the other hand, killing by the process name is useful when you want to kill all running instances of a particular program. Killing by the process ID is useful when you want to kill only a specific process. The PID is a number that uniquely identifies a process. ![]() Depending upon the situation, you can use one of these commands for this purpose.Īs we will see later in this article, you can kill a process by its name or its process ID (PID). You can do this through three commands - top, ps, pidof and pgrep. In order to kill a process, you should first locate the details of the process. In this article, we will look at various tools you can use to kill processes on a Linux system. In this situation, you would want to manually “kill” the process. However, sometimes a process can hang up or consume a lot of CPU or RAM. Usually, a process terminates on its own when they’re done with their task, or when you ask them to quit by pressing a keyboard shortcut or clicking on the “Close” button. Such programs which are running on the system are called “processes”. In an operating system, there are many programs, which may be either run by an user or by the OS itself (such as system services).
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