To display the IP address on the lo.txt

To display the IP address on the login screen using /etc/issue on Debian 11, you can modify the contents of the file and use a script to dynamically insert the IP address.

Here are the steps to modify /etc/issue and create the script:

Create a backup copy of the /etc/issue file before modifying it:
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sudo cp /etc/issue /etc/issue.bak
Edit the /etc/issue file with a text editor:
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sudo nano /etc/issue
Add the following line to the file:
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IP Address: \4
This line specifies that the IP address should be inserted using the \4 escape sequence.

Save the changes and exit the text editor.

Create a script that retrieves the IP address and inserts it into /etc/issue. Create a file called /usr/local/bin/insert-ip.sh with the following contents:

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#!/bin/bash

ip=$(ip addr show | grep -w inet | awk '{print $2}' | awk -F/ '{print $1}')
sed -i "s/\\\4/$ip/" /etc/issue
This script retrieves the IP address and replaces the \4 escape sequence in /etc/issue with the actual IP address.

Make the script executable:
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sudo chmod +x /usr/local/bin/insert-ip.sh
Edit the /etc/rc.local file to execute the script at boot:
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sudo nano /etc/rc.local
Add the following line before the exit 0 line:
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/usr/local/bin/insert-ip.sh
This line specifies that the insert-ip.sh script should be executed at boot.

Save the changes and exit the text editor.
That's it! The next time the workstation boots, the IP address should be displayed on the login screen. Note that this method modifies the /etc/issue file, which is used by many other system utilities, so be careful when modifying its contents. Also, note that modifying /etc/rc.local is not the recommended method to execute scripts at boot time. For a more modern approach, you can create a systemd service as described in my previous answer.