Master Linux System Services: List, Check, and Manage with systemd & netstat

Linux system services (daemons) start automatically at boot and stop on shutdown. This article shows how to list all running services and check their status on CentOS/RHEL 7.x and older SysV init systems using systemd, netstat, and the /etc/services file.

Viewing systemd services on CentOS/RHEL 7.x

CentOS 7 uses systemd, replacing traditional daemon commands with systemctl. To list unit files:

systemctl list-unit-files

To list all active services:

systemctl | more

To list only services:

systemctl list-units --type service

You can pipe the output to grep to search for a specific service, e.g.:

systemctl | grep "apache2"

Using netstat to view services and listening ports

The netstat command displays active network connections, interface statistics, and routing tables. To show services and their listening ports:

netstat -pnltu

Inspecting the /etc/services file

The file /etc/services is an ASCII list of service names, port numbers, protocols, and aliases. You can view it with any text editor, for example:

vim /etc/services

Checking the status of a specific systemd service

Use systemctl status <service_name> to see detailed status. Example for OpenSSH:

systemctl status sshd

To test whether a service is active:

systemctl is-active sshd

To check if a service is enabled at boot:

systemctl is-enabled sshd

Viewing service status on older SysV init systems

On systems still using SysV init, the service command reports status. Example for OpenSSH:

service sshd status

To list all services and their statuses, you can use:

chkconfig --list