Network Services Overview SMTP
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
Lab Setup
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 packages needed to provide the service
Install the service
yum install postfix
Configure SELinux to support the service
- Service agnostic → Ensure SELinux is running and enabled (RHCSA objective).
Use SELinux port labeling to allow services to use non-standard ports
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!
Configure the service to start when the system is booted
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
Configure the service for basic operation
Enable and Start the service
systemctl enable postfix
systemctl start postfix
Configure host-based and user-based security for the service
Firewall
Allow access through the firewall
firewall-cmd --permanent --add-service=smtp firewall-cmd --reload