Add IP address on login prompt

Adding information about the IP address of a linux machine to the login prompt

Things to know

Getting the IP address

The IP address for the current machine can be obtained entering the following command:

hostname -I

Startup scripts

There are some default scripts run after particular events.

The one I want (after startup) it’s located in /etc/rc.local

Login prompt message

The login message it’s handled by the agetty command and documentation about it can be found using man agetty.

The agetty command displays and interprets the content of the /etc/issue file.

Mixing all this togheter

At startup I need to get the IP address of the machine and append it to the issue file to be printed out at the login screen.

First thing to do is to create a copy of the /etc/issue file.

This can be done with the command:

sudo cp /etc/issue /etc/issue.base

The next thing to do is to edit the /etc/rc.local file to:

• gather the  current IP address
• copy /etc/issue.base back to /etc/issue
• append to /etc/issue a new line with a string like IP address: xxx.xxx.xxx.xxx

This can be done editing the original /etc/rc.local that should look like this:

	#!/bin/sh -e
	#
	# rc.local
	#
	# This script is executed at the end of each multiuser runlevel.
	# Make sure that the script will "exit 0" on success or any other
	# value on error.
	#
	# In order to enable or disable this script just change the execution
	# bits.
	#
	# By default this script does nothing.
	exit 0

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rc.local

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To look like this:

	#!/bin/sh -e
	#
	# rc.local
	#
	# This script is executed at the end of each multiuser runlevel.
	# Make sure that the script will "exit 0" on success or any other
	# value on error.
	#
	# In order to enable or disable this script just change the execution
	# bits.
	#
	# By default this script does nothing.
	BASE_ISSUE_FILE="/etc/issue.base"
	CURRENT_ISSUE_FILE="/etc/issue"
	CURRENT_IP_ADDRESS=$(hostname -I)
	cat $BASE_ISSUE_FILE > $CURRENT_ISSUE_FILE
	echo "IP Address:" $CURRENT_IP_ADDRESS >> $CURRENT_ISSUE_FILE
	exit 0

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rc.local

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After a reboot the login prompt should look like this:

Ubuntu 16.04.1 LTS ubuntu-base-vm tty1

IP Address: 192.168.1.5
ubuntu-base-vm login: