Command to check services in linux

How to check running process in Linux using command line

I am a new system administrator for the Linux operating system. How do I check running process in Linux using the command line option?

Tutorial details
Difficulty level	Easy
Root privileges	Yes
Requirements	Linux terminal
Est. reading time	4 mintues

One can use the Linux command line or terminal app to display a running process, change their priorities level, delete process and more. This page shows how to use various commands to list, kill and manage process on Linux.

Check running process in Linux

The procedure to monitor the running process in Linux using the command line is as follows:

1. Open the terminal window on Linux
2. For remote Linux server use the ssh command for log in purpose
3. Type the ps aux command to see all running process in Linux
4. Alternatively, you can issue the top command or htop command to view running process in Linux

Let us see some example and usage in details.

Please note that vivek@nixcraft:

$ is my shell prompt. You need to type commands after the $ prompt.

How to manage processes from the Linux terminal

The ps command is a traditional Linux command to lists running processes. The following command shows all processes running on your Linux based server or system:
vivek@nixcraft:

$ ps -aux
vivek@nixcraft:

1. root – User name
2. 1 – PID (Linux process ID)
3. 19:10 – Process start time
4. /sbin/init splash – Actual process or command

There may be too many processes. Hence, it uses the following less command/more command as pipe to display process one screen at a time:
vivek@nixcraft:

$ ps -aux | more
vivek@nixcraft:

$ sudo ps -aux | less
Press q to exit from above Linux pagers. You can search for a particular Linux process using grep command/egrep command:
vivek@nixcraft:

$ ps aux | grep firefox
vivek@nixcraft:

$ sudo ps aux | grep vim
vivek@nixcraft:

$ sudo ps -aux | egrep ‘sshd|openvpn|nginx’

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Linux pgrep command

Many variants of Linux comes with the pgrep command to search/find process. The syntax is:
vivek@nixcraft:

$ sudo pgrep sshd
vivek@nixcraft:

$ pgrep vim
vivek@nixcraft:

$ pgrep firefox
vivek@nixcraft:

Linux top command

The top command is another highly recommended method to see your Linux servers resource usage. One can see a list of top process that using the most memory or CPU or disk.
vivek@nixcraft:

$ sudo top
vivek@nixcraft:

Linux htop command to check running process in Linux

The htop command is an interactive process viewer and recommended method for Linux users. One can see a list of top process that using the most memory or CPU or disk and more:
vivek@nixcraft:

$ sudo htop
vivek@nixcraft:

Linux kill command

Want to kill a process? Try kill command. The syntax is:
vivek@nixcraft:

$ kill pid
vivek@nixcraft:

$ kill -signal pid
Find PID using ps, pgrep or top commands. Say you want to kill a PID # 16750, run:
vivek@nixcraft:

$ kill 16750
For some reason if the process can not be killed, try forceful killing:
vivek@nixcraft:

$ kill -9 16750
OR
vivek@nixcraft:

$ kill -KILL 16750

Linux pkill command

If you wish to kill a process by name, try pkill command. The syntax is:
vivek@nixcraft:

$ pkill processName
vivek@nixcraft:

$ pkill vim
vivek@nixcraft:

$ pkill firefox
vivek@nixcraft:

$ pkill -9 emacs
vivek@nixcraft:

$ sudo pkill -KILL php7-fpm

Linux killall command

The killall command kills processes by name, as opposed to the selection by PID as done by kill command:
vivek@nixcraft:

$ killall vim
vivek@nixcraft:

$ killall -9 emacs

Linux nice and renice command

The primary purpose of the nice command is to run a process/command at a lower or higher priority. Use the renice command to alter the nice value of one or more running Linux processes. The nice value can range from -20 to 19, with 19 being the lowest priority. Say, you want to compile software on a busy Linux server. You can set a very low priority, enter:
vivek@nixcraft:

$ nice -n 13 cc -c *.c &
Set a very high priority for a kernel update. Before rebooting Linux server, run:

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Command to check services in linux

Last updated on: 2019-12-20

Authored by: Rackspace Support

When you need to troubleshoot a network service, the first step is to ensure that the service is running.

If the service has an initialization (init) script installed, you can use the service command to start, stop, and check the status of the service. This command references a service by using its init script, which is stored in the /etc/init.d directory for Debian®-based distributions and the etc/rc.d/init.d directory for Red Hat®-based distributions.

If you don’t know the name that the system uses for a service, check either of the preceding directories by using the ls command followed by the directory name. Some names vary depending on your distribution. For example, Apache® is httpd on CentOS® and apache2 on the Ubuntu® operating system.

Note: Many newer Linux® distributions use systemd instead of netstat to check services. If you’re using systemd , replace all service commands with systemct1 . For more information about systemct1 commands, see the Fedora™ SysVinit to Systemd Cheatsheet.

Check the service status

A service can have any of the following statuses:

• start : The service has started.
• stop : The service has stopped running.
• restart : The service is rebooting and will start after the process is complete.

The following example shows how to check the status of httpd on CentOS by using the service command:

Start the service

If a service isn’t running, you can use the service command to start it. The following example starts the httpd service:

If the application can’t be started, the system reports the failure and usually displays a message that indicates the cause of the problem.

Use netstat to find port conflicts

In the preceding example, httpd can’t be started because something is already listening on the port. To find out what’s listening, you can run the netstat command.

Run the following command to display a list of listening programs and the ports that they’re using:

The output shows that the nc program (which appears in the Program name column) is listening on port 80 (which appears in the Local Address column). Stopping this program should enable httpd to be started.

Note: For more information about the netstat command, see Check listening ports with netstat.

Check xinetd status

If the service isn’t running, it might be because a super-server such as an Extended Internet Service Daemon ( xinetd ) is being used to launch the program when a connection is received. If this is the case, starting the service might have resolved the issue. Run the following command to verify that the issue is resolved:

Check logs

If you can’t start your service, review your logs to see if they contain information about the issue.

Next steps

After you’re sure that the application is running, check the server resources to verify how much your application is consuming.

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Red Hat / CentOS Check and List Running Services Linux Command

H ow do I list all currently running services in Fedora / RHEL / CentOS Linux server? How can I check the status of a service using systemd based CentOS/RHEL 7.x and RHEL/CentOS 8.x?

There are various ways and tools to find and list all running services under a Fedora / RHEL / CentOS Linux systems.

Tutorial details
Difficulty level	Easy
Root privileges	Yes
Requirements	RHEL or CentOS Linux
Est. reading time	6 minutes

Red Hat / CentOS Check and List Running Services Command

Please note that systemd based system such as CentOS/RHEL 7.x/8.x and latest version of fedora use the systemctl command to list running services

List running services using service command on a CentOS/RHEL 6.x or older

The syntax is as follows for CentOS/RHEL 6.x and older (pre systemd systems) :
service —status-all
service —status-all | more
service —status-all | grep ntpd
service —status-all | less

Print the status of any service

To print the status of apache (httpd) service:
service httpd status
Display status of sshd service:
service sshd status

List all known services (configured via SysV)

List service and their open ports

Turn on / off service

ntsysv
chkconfig service off
chkconfig service on
chkconfig httpd off
chkconfig ntpd on
ntsysv is a simple interface for configuring runlevel services which are also configurable through chkconfig. By default, it configures the current runlevel. Just type ntsysv and select service you want to run.

Red Hat / CentOS List Running Services using systemctl ( RHEL/CentOS 7.x/8.x )

If you are using systemd based Linux distros such as Fedora Linux v22/23/24/26/27/28/29/30/31 or RHEL/CentOS Linux 7.x/8.x. Try the following command to list running services using the systemctl command. It control the systemd system and service manager.

To list systemd services on CentOS/RHEL 7.x+ use

The syntax is:
systemctl
systemctl | more
systemctl | grep httpd
systemctl list-units —type service
systemctl list-units —type mount
To list all services:
systemctl list-unit-files
Sample outputs:

Fig.01: List all units installed on the CentOS /RHEL 7 systemd based system, along with their current states

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How to List Services in Linux

In this article, I will show you how to list all running services on Linux. We will also check how to check the status of a service on a systemd system.

Let’s learn different commands used to list services on Centos/RHEL 7.x.

Check and Listing linux services (systemd on Centos/RHEL 7.x)

To list systemd services we will use systemctl command as below

Sample Output

To list active systemd services run

Sample Output

Another command you can use is

Sample Output

You can pipe the output to grep to search a more specific service as shown below

Output

Listing services using Netstat Command

Nestat command is a tool used for examining active network connections, interface statistics as well as the routing table. It’s available in all Linux distributions and here we will check how to list services using netstat command.

To check the services alongside the ports they are listening.

Output

Viewing /etc/services file

The /etc/services is an ASCII file that contains information about numerous services that client applications might use on the computer. Within the file is the service name, port number and protocol it uses, and any applicable aliases. ITO put t indicates whether a service is TCP or UDP and the name it goes by according to IANA. This information is helpful especially if you are unsure which service is running on which port by default.

To get a clearer picture, view the /etc/services file using a text editor of your choice.

Output

Systemd services status check

In newer versions of Linux, Systemd init is present. To check if a service is running, use the syntax below

Syntax

For example, to check if OpenSSH is running on your system, run

Output

Alternatively, you can use the syntax below to check if the service is active

In this case, to check if OpenSSH is active, execute

Output

Also, you can use the command below to check if a service is enabled

To check if OpenSSH is enabled, run

Output

Checking the status of services in older systems (Centos/Rhel 6.x)

For systems running SysV Init, you can check the status of services by running

For example, to check the status of OpenSSH, run

Output

You can also check all services by running

Output

We hope you found this article useful. Feel free to try out some of the systemd commands listed here.

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