How to Customize Your MOTD: A Complete Guide

Introduction

Ever logged into a server and been greeted by a message? That’s the MOTD, or Message of the Day. It’s a simple yet powerful tool to provide information, welcome users, or display important system alerts. But the default MOTD is often bland. This guide will teach you exactly how do I change my motd and transform it into something more informative and personalized. We’ll explore different methods, catering to various Linux systems and skill levels. Whether you want to add a personal touch, display critical system statistics, or strengthen security awareness, this article will provide you with the knowledge to customize your MOTD effectively.

Understanding the Fundamentals of MOTD

The Message of the Day isn’t just a random blurb; it’s a purposeful communication tool. Think of it as a digital welcome mat, providing essential information as soon as someone logs into a system. It appears upon a successful login, typically through SSH or a local terminal.

The heart of the MOTD lies in specific files. One of the most common is /etc/motd. This file holds a static message, meaning its content remains constant unless manually changed. However, modern systems often utilize a directory called /etc/motd.d/. Within this directory, individual script files reside. These scripts, when executed, generate dynamic content that’s concatenated to form the complete MOTD.

To modify the MOTD, you’ll typically need root privileges or a user account with sudo access. These elevated permissions are necessary because you’re altering system-level configuration files. Without them, you won’t be able to save changes to /etc/motd or /etc/motd.d/.

Distinguishing between static and dynamic MOTDs is crucial. A static MOTD, controlled by /etc/motd, is simple to manage. You simply edit the file’s content. A dynamic MOTD, driven by scripts in /etc/motd.d/, allows for more complex and informative displays, pulling real-time system information. The choice depends on your needs and technical comfort level.

Changing the Static MOTD

The most straightforward way to customize your MOTD is by editing the /etc/motd file. This method is perfect for displaying simple, unchanging messages. Here’s a step-by-step guide:

First, open the /etc/motd file using a text editor. Popular choices include nano, vim, or emacs. Because this is a system file, you will need to use sudo before the command. For instance, to use nano, you’d type sudo nano /etc/motd in your terminal.

Next, once the file is open, carefully delete the existing content. The default MOTD is often generic, so feel free to erase it completely.

Then, type your new message. This could be a simple welcome, a company motto, or a security reminder. Be mindful of the terminal width and avoid overly long lines.

Finally, save the file. In nano, you can typically press Ctrl+X, then Y to confirm saving, and then Enter. In vim, press Esc, then type :wq and press Enter.

When formatting your message, keep it concise and easy to read. While you can experiment with ASCII art, consider its accessibility. Some users may have terminal settings that don’t display it correctly. Color codes can add visual flair, but ensure they are compatible with most terminals. Not all terminal emulators support color, leading to garbled output if you overdo it.

Here are a few examples of static MOTD messages:

A simple welcome


Welcome to the Server!


Basic system information


System: Ubuntu Server
Contact: admin@example.com


Security warning


Unauthorized access is prohibited.
All activity is logged.


Working with Dynamic MOTD

For a more informative and dynamic MOTD, leverage the /etc/motd.d/ directory. This approach allows you to display real-time system statistics, making the MOTD a valuable source of up-to-date information.

The way /etc/motd.d/ works is quite clever. Each file within the directory is treated as an executable script. When a user logs in, these scripts are executed in alphabetical order. The output of each script is then concatenated (joined together) to create the final MOTD displayed to the user.

To create a new dynamic MOTD script, follow these steps:

First, create a new file in the /etc/motd.d/ directory. Choose a descriptive filename, such as 00-uptime or 10-cpu-usage. The numbers at the beginning help control the execution order. Again, use sudo to create these files.

Then, make the file executable. This is essential for the script to run. In the terminal, use the command sudo chmod +x /etc/motd.d/your-script-name.

Next, write the script. Bash scripting is commonly used. Here’s a simple example that displays system uptime:


#!/bin/bash
echo "System Uptime: $(uptime | awk '{print $3, $4, $5}')"


Finally, test the script. Before relying on it, execute it directly from the command line to ensure it produces the desired output. For example: sudo /etc/motd.d/00-uptime.

Here are more examples of dynamic MOTD scripts:

Displaying CPU usage


#!/bin/bash
echo "CPU Usage: $(top -bn1 | grep "Cpu(s)" | sed "s/.*, *\([0-9.]*\)%* id.*/\1/" | awk '{print 100 - $1}')%"


Displaying disk space


#!/bin/bash
echo "Disk Space:"
df -h | grep '^/dev/' | awk '{printf "%-15s %8s %8s %8s %5s%% %s\n", $6, $2, $3, $4, $5, $1}'


Displaying the number of logged-in users


#!/bin/bash
echo "Logged-in Users: $(who | wc -l)"


When working with dynamic MOTD, be mindful of script execution time. Avoid complex or slow scripts that could delay the login process. Also, consider the security implications of running scripts, especially if they come from untrusted sources. Carefully review the script’s content before deploying it.

Considerations for Advanced Customization

While /etc/motd and /etc/motd.d/ are the primary methods, some systems offer more advanced customization options.

On Debian and Ubuntu-based systems, you might encounter the update-motd system. This system provides a framework for managing dynamic MOTD scripts. You can enable or disable specific scripts using the update-motd command. Check your distribution’s documentation for specific usage instructions.

Pluggable Authentication Modules, or PAM, offer another layer of customization. PAM is a system for managing authentication in Linux. The pam_motd module allows you to configure the MOTD based on various factors, such as user groups or login methods. However, PAM configuration can be complex and requires a deeper understanding of system administration.

It’s also possible to customize the MOTD based on user roles using bash scripting. This involves checking the user’s group membership and displaying different messages accordingly. While more intricate, this approach allows for tailored information based on user privileges.

Troubleshooting Common MOTD Issues

Sometimes, the MOTD doesn’t display correctly, or at all. Here’s a troubleshooting guide to address common issues:

If the MOTD isn’t showing up, first check the permissions on /etc/motd and the files within /etc/motd.d/. They should be readable and, in the case of scripts, executable. Use the ls -l command to verify permissions.

Also, check the SSH configuration file, typically located at /etc/ssh/sshd_config. Ensure the PrintMotd option is set to yes. If it’s commented out or set to no, the MOTD will not be displayed during SSH logins.

If you’re using a dynamic MOTD, carefully check for errors in your scripts. Use the bash -x /etc/motd.d/your-script-name command to debug the script and identify any issues.

Incorrect character display is another common problem. This is often due to encoding issues. Ensure your terminal and the MOTD file are using the same encoding, preferably UTF-8. If you’re using special characters or symbols, test them across different terminals to ensure compatibility.

If the MOTD is showing old information, especially with dynamic scripts, it could be due to caching. Some systems cache the output of MOTD scripts to improve performance. You may need to clear the cache or modify the scripts to ensure they fetch the latest information.

Essential Security Considerations

While customizing your MOTD, it’s vital to keep security in mind. Avoid displaying sensitive information, such as internal IP addresses or exact software versions. This information could be valuable to attackers.

Exercise caution when using dynamic MOTD scripts from untrusted sources. These scripts could potentially contain malicious code that could compromise your system. Always review the script’s content before deploying it.

Finally, regularly review your MOTD for accuracy and security. Ensure the information is up-to-date and that no sensitive details are being inadvertently exposed.

Concluding Thoughts

Changing your MOTD is a straightforward way to add a personal touch and enhance the user experience on your system. Whether you opt for a simple static message or a dynamic display of system statistics, the possibilities are vast.

Now that you know how do I change my motd, don’t hesitate to experiment and tailor it to your specific needs. Customize it to provide helpful information, promote your brand, or simply add a touch of personality to your server.

For further learning and more in-depth information, explore the official documentation for your Linux distribution and the PAM modules. There are also numerous online tutorials and communities dedicated to Linux system administration where you can find inspiration and support. Happy customizing!