Tech Tutorial: Deploy, Configure, and Maintain Systems - Managing Services on RHEL #

Introduction #

In this tutorial, we will focus on a critical aspect of managing Red Hat Enterprise Linux (RHEL) systems, particularly starting, stopping, and configuring services to start automatically at boot. This skill is essential for system administrators as services control how the Linux system behaves at runtime and ensures necessary applications and functions are available when the system is in use.

What are Services? #

In Linux, a service (or daemon) is a background process that is designed to run independently of user sessions. These services include web servers, database servers, and system services like logging, scheduling, and printing.

Systemd and systemctl #

RHEL 7 and later versions use systemd as the init system, which provides a system and service manager that runs as PID 1 and starts the rest of the system. systemd uses a command called systemctl to control the state of systemd services.

Step-by-Step Guide #

1. Checking the Status of a Service #

To check the status of a service on RHEL, you can use the systemctl status command. For instance, to check the status of the HTTPD (Apache web server), you would use:

sudo systemctl status httpd

This command provides detailed output including whether the service is active, loaded, enabled, and any recent log entries.

2. Starting and Stopping Services #

To start a service immediately, use the systemctl start command:

sudo systemctl start httpd

Stopping a service is just as straightforward:

sudo systemctl stop httpd

3. Enabling and Disabling Services at Boot #

To ensure a service starts automatically at boot, you must enable it:

sudo systemctl enable httpd

This command creates a symbolic link from the service’s script in /etc/systemd/system/ to the appropriate directory under /etc/systemd/system/. If you decide that you don’t want the service to start at boot anymore, you can disable it:

sudo systemctl disable httpd

This removes the symbolic link.

4. Restarting and Reloading Services #

If you need to restart a service (stop and then start), you can use:

sudo systemctl restart httpd

If the service supports reloading configuration files without interrupting active processes, you can use:

sudo systemctl reload httpd

Detailed Code Examples #

Let’s go through a real-world scenario where we configure a new RHEL system to run a web server that needs to start automatically at boot.

1. Install the HTTPD Service:

   First, we need to install the Apache HTTP Server:

   sudo yum install httpd
   

2. Start and Enable HTTPD Service:

   sudo systemctl start httpd
   sudo systemctl enable httpd
   

3. Verify the Service is Running and Enabled:

   sudo systemctl status httpd
   

   Look for active (running) in the output and enabled to confirm that it’s set to start at boot.

4. Configure HTTPD to Serve a Custom Website:

   Edit the configuration file and add your website details. Usually, you might edit /etc/httpd/conf/httpd.conf or add files under /etc/httpd/conf.d/.

5. Reload the HTTPD Configuration:

   After making configuration changes, reload the service to apply them without stopping the service:

   sudo systemctl reload httpd
   

Conclusion #

Managing services effectively on RHEL using systemctl is a foundational skill for any system administrator. This tutorial covered how to start, stop, enable, disable, restart, and reload services. Mastery of these commands ensures you can keep essential services running smoothly and respond effectively to changes in system configuration or requirements. Remember, careful management of services is critical to maintaining the reliability and security of your Linux environment.