kill is a command which is used in several popular operating systems to send signals to running processes. In Linux kill command is normally used to terminate running process. In this article we will cover basics of kill command so you will understand it and apply it in your environment.

Before killing or terminating any process we have to get its process ID (PID) or process name. We can use wo commands to find process ID’s, first is “ps” command and the second it “top” command. In this article we will use ps command to find a process ID and its name.

Locate process using ps command

ps command is used to see processes, following command to list all running processes.

ps aux

a: Show processes for all users
u: Display the user who is using the process
x: Show all processes. (it also show the processes running in a GUI environment)

List specific process ID

If you want to search any specific process so you can use any of following three methods.

Method 1:

ps -aux | grep process-name

e.g check for Apache process

ps -aux | grep httpd

You can see process id’s of Apache in above image.

Method 2: Use pidof command

pidof httpd

Sample outputs:

4372 4371 4370 4369 4368 4361

Method 3: Use pgrep command

pgrep httpd

All above methods will show process ID’s of httpd (Apache) process.

Kill Process

kill command is use to terminate or kill running processes.

Method 1: Kill process by its process ID

Now, I will kill one Apache process using its process ID.

kill -9 4372

Then, verify that PID is killed

pidof httpd

So you can see in above image that process 4372 is no more exist.

Method 2: Kill process by its name

If you want to kill all the processes of a service you can use this method.

kill -9 httpd

OR

pkill httpd

Now, verify process is killed.

pidof httpd

Then, you will see that all processes of httpd will no more exist.

Kill all processes of a User

You can use below command to show processes of a user.

ps -fu user-name

Now you will get process ID’s of that user. E.g I show process ID’s of user “osradar” in below image

Then, run below command to kill all processes of the user

kill -HUP process-ids

So, when you run again below command you will see no result.

ps -fu user-name

That’s it, You now know that how to kill running processes in Linux.

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Today we introduce you to HTOP, an interactive process viewer for Unix systems. It is a text-mode application (for console or X terminals) and requires ncurses. HTOP is also presented as a natural evolution of TOP (although its developments are totally independent), it has a better organization of information and thanks to its colors, we can easily observe every detail of the processes that are running at that time on our pc.

Installing HTOP in many  GNU/LINUX distributions

One of the biggest advantages of HTOP is that it is available through the official repositories for almost all GNU/LINUX distributions: it is only a single command away on the terminal to install it!! Although of course the command is defined by the distribution we are using.

Install HTOP on Debian, Ubuntu and ubuntu-based

Debian, Ubuntu and Ubuntu derivatives use apt as package manager, so the command to run with root privileges is as follows:

apt install htop

Or if the user has permission to use sudo, it can also be used:

sudo apt install htop

Install HTOP on Fedora

Fedora uses the dnf package manager and therefore the command to install HTOP is the following, I remind you that you must have root privileges:

dnf install htop

And after downloading, it will be installed.

Install HTOP on Gentoo

HTOP is also available from the Gentoo package manager called emerge. With root permissions we can use this command to install it:

emerge sys-process/htop

Install HTOP on CentOS 7

CentOS 7 a free alternative to Red Hat Linux Enterprise, the process is a little more complicated than previous distributions but it’s no big deal.

Once logged in as root user, we proceed to download the package containing the EPEL repository:

wget http://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm

Then we must install the downloaded.rpm package that will add the desired repository.

rpm -Uvh epel-release-latest-7.noarch.rpm

Later we verify that the repository is added correctly.

yum repolist

And if EPEL appears in the repository list, we did it correctly and it would already be added.

Now we proceed to install HTOP with the following command:

yum install htop

Now we have HTOP installed in our CentOS 7.

Using HTOP

HTOP as we saw it can be installed on various GNU/LINUX distributions but is also available for Unix and derivatives. For this article we will use HTOP installed on CentOS7.

The command that executes htop is htop 🙂 this command does not need to be executed as root user. Once the command is written and executed, htop will immediately appear in the open terminal session.

exit

htop

This is the screen that is displayed when you run htop. We can notice how it gives us information about CPU or ram memory usage, and the list of all processes running at the moment. However, if we are a little more observant, we will notice that, the HTOP command line interface can be divided into 3 big parts:

• The first shows CPU usage with percentages, RAM and swap memory. On the right side of the header, displays the active tasks and more.

• The second section or main header shows all the active processes of the system.

Each column represents an information or detail, in this header is where most of the HTOP possibilities take place. These are the columns with the information they show:

• PID: Displays the process identifier number.
• User: The user tells us that he has activated this process.
• PRI: It shows the priority with which the process is executed.
• NI: Shows the priority level
• VIRT: The number of virtual memory used by the process.
• RES: Used ram memory (Megabytes)
• SHR: Shared memory used
• S: Process status (Running, sleeping or zombie)
• CPU%: percentage of CPU used by the process
• MEM%: percentage of ram memory used by the process
• TIME+: Active life-time of the process
• Command: The command that executes the process.

As we can see, we have a lot of information available from HTOP.

The last “section” is intended for different actions that HTOP allows us to execute, for example, show help, kill processes, search, sort or exit.

Killing a process with HTOP

Of these options, we usually use more often that of killing a process. To kill a process we must first use the arrow keys to navigate from top to bottom to position ourselves in the process to be killed, then press the F9 key, and then move with the keyboard to option 9:

And by pressing the F5 key we can switch between the sorted or tree-shaped view:

Conclusively, HTOP is a great application executed on the terminal to monitor processes within our Unix-based operating system. Its installation process is quite simple and this is reflected in the large number of GNU/LINUX distributions that have it within their main repositories.

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The post HTOP: How to install it and use it? appeared first on Linux Windows and android Tutorials.