ar51an / raspberrypi-motd

Dynamic Message Of The Day (MOTD) For Raspberry Pi

MOTD

Customized dynamic message of the day (motd) for Raspberry Pi

              

Preview

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Intro

Many folks use Raspberry Pi as headless. If you use SSH more often to connect Raspberry Pi and interested in changing the MOTD (message of the day), keep on reading. The goal is to create simple, swift and useful motd.

Lack of available update count in RaspiOS motd is the triggering point to develop this motd. Traditionally apt-check utility in update-notifier-common package was used to fetch the available update count. This package is no longer available from buster onwards, its functionality is merged into unattended-upgrades add-on package. I used apt-get to parse the required information.

The process used for the motd is the same as RaspiOS or Ubuntu uses to show the motd dynamically. There is no additional package or third party tool used. It is written in bash and executes using the same mechanism as the default motd. There are multiple commands for retrieving the same information. I tested various commands for each info and used that took the least amount of time. This dynamic motd takes approximately 1 sec after authentication. This is the fastest you can get with all the information it is displaying.

Specs:

HW	OS
Raspberry Pi 4 Model B	raspios-bookworm-arm64-lite

Steps

❯ Remove Default MOTD

• Delete /etc/motd. This file contains the static text about Debian GNU/Linux liability. Alternatively you can keep a backup of this file at some place.

  sudo rm /etc/motd

• Delete /etc/update-motd.d/10-uname. This file prints the OS version dynamically to the default message. New motd will print a trimmed down version of OS.

  sudo rm /etc/update-motd.d/10-uname

• Modify /etc/ssh/sshd_config. This file prints last login timestamp and location. New motd will print last login timestamp and location.

  sudo nano /etc/ssh/sshd_config
  Add: PrintLastLog no
  Save & Exit
  Restart sshd: sudo systemctl restart sshd

NOTE:
Default motd is completely removed. Reconnect ssh session and if you followed the steps correctly you will not see any motd.

❯ Implement New MOTD

• Copy 10-welcome, 15-system and 20-update scripts from the latest release under update-motd.d dir to /etc/update-motd.d dir. Make sure scripts are under the ownership of root and are executable.

  Change ownership [If needed]:
  sudo chown root:root /etc/update-motd.d/<script-name>

  Make scripts executable [If needed]:
  sudo chmod +x /etc/update-motd.d/<script-name>

  

NOTE:
If you noticed all the scripts have names starting with a number. Dynamic contents of the motd are created by PAM (Pluggable Authentication Module) running bash scripts from /etc/update-motd.d dir. Scripts are read in numeric order and do not need a file extension. In the default motd it was executing 10-uname script to show the OS version which we deleted earlier.

• Create static contents of new motd. This is not entirely static, PAM will execute static script. Static script is created from dynamic script once a day with systemd timer. It minimizes startup delay. Keeping it completely dynamic increases startup delay to 3-4 seconds after authentication.

  • Create dir /etc/update-motd-static.d

    sudo mkdir /etc/update-motd-static.d/

  • Copy 20-update script from the latest release under update-motd-static.d dir to this newly created dir /etc/update-motd-static.d. Make sure script is under the ownership of root and it is executable.

    Change ownership [If needed]:
    sudo chown root:root /etc/update-motd-static.d/20-update

    Make script executable [If needed]:
    sudo chmod +x /etc/update-motd-static.d/20-update

    

  • Run dynamic script to update the static script /etc/update-motd.d/20-update with pending update count (if any). We will automate this process through systemd timer.

    Run script:
    sudo run-parts /etc/update-motd-static.d

NOTE:
New motd is implemented, pending few automations. Let's test new motd to verify that everything is working properly. Either reconnect ssh session or run the new motd from the same shell. If steps were followed correctly you will see new motd, something similar to the preview.

Run motd from the same shell:
sudo run-parts /etc/update-motd.d

❯ Automation

• We need to automate the process of finding pending OS update count. It is scheduled to run once a day at 8:00pm. You can change the time and frequency based on your preference.

  • Systemd Timer
    Copy motd-update.timer and motd-update.service from the latest release under systemd-timer dir to /etc/systemd/system. Make sure files are under the ownership of root. Enable and start timer.

    Change ownership [If needed]:
    sudo chown root:root /etc/systemd/system/motd-update.timer
sudo chown root:root /etc/systemd/system/motd-update.service
    Enable timer:
    sudo systemctl enable motd-update.timer
    Start timer:
    sudo systemctl start motd-update.timer
    List all timers [If needed]:
    systemctl list-timers

• Last step. We need to reset the pending update count in motd as soon as we update the OS, otherwise count will be updated at the next run of systemd timer. Suppose you update system with commands sudo apt update & sudo apt full-upgrade. You need to run command sudo run-parts /etc/update-motd-static.d at the end. It will reset the update count in motd after OS update. Whatever your preferred way to update the OS, run this command at the very end.

  • I update OS with a bash script update.sh after seeing pending updates in motd. It takes care of everything that includes update OS, cleanup and update motd count. update.sh is available in the latest release under update-os dir. Execution screenshot is shown in the repo under update-os dir. Script is well documented. Open and check the commands once before execution.
    You can add switch -y to sudo apt full-upgrade command to bypass the yes/no prompt. I prefer not to have it as a last chance to review. Script does cleanup as well using sudo apt --purge autoremove & sudo apt clean, you can remove them if you prefer not to run these after OS update.

NOTE:
If you are not seeing the exact colors in your motd as in the preview, check the Putty section below for color scheme.

Scripts Info

❯ /etc/update-motd.d/10-welcome

Displays the raspberry model, welcome user message, current timestamp and kernel version.

❯ /etc/update-motd.d/15-system

Shows various details of the system. It includes temperature, memory, running processes and others. Few labels are trimmed down, like Procs for Processes, Temp for Temperature, Last for Last Login. You can use full labels according to your preference and arrange them accordingly.

❯ /etc/update-motd.d/20-update

This static script displays available update count. It is generated by /etc/update-motd-static.d/20-update.

❯ /etc/update-motd-static.d/20-update

Calculates available update count and generates the static script for motd display. It can be expanded to show the security update count separately like Ubuntu.

PuTTY

I use slight modification of Liquid Carbon PuTTY theme from AlexAkulov. Modified theme Liquid Carbon Mod.reg is available under this repo folder putty along with screenshots of PuTTY settings.