General Information

This page covers the Network Services objectives, specifically for SMTP.

Network Services Objectives

• Install the packages needed to provide the service
• Configure SELinux to support the service
• Use SELinux port labeling to allow services to use non-standard ports
• Configure the service to start when the system is booted
• Configure the service for basic operation
• Configure host-based and user-based security for the service

The following virtual machines will be used:

• server1.example.com (192.168.1.150) → Configure SMTP null client (on the exam)
• server2.example.com (192.168.1.151) → Configure central mail server for client testing (NOT on the exam)

Install the service

yum install postfix

• Service agnostic → Ensure SELinux is running and enabled (RHCSA objective).

Configuring the <service-name> with a non standard port and allowing port access with selinux.

NOTE: “man semanage-port” has examples for allowing non-standard ports!

Check Current Service Status

systemctl status postfix

• Also displays if the service is enabled or disabled

Enabling a service to start on boot

systemctl enable postfix

Enable and Start the service

systemctl enable postfix
systemctl start postfix

Allow access through the firewall

firewall-cmd --permanent --add-service=smtp
firewall-cmd --reload