IP Checker

Requirements

Script tested on Ubuntu server 22.04 LTS for ARM on a Raspberry PI 4. The mail was sent using a gmail account. You must install the ssmtp package with the following commands :

sudo apt update
sudo apt install ssmtp 

Then you must set up an account in /etc/ssmtp/ssmtp.conf

sudo nano /etc/ssmtp/ssmtp.conf

With a Google account, since May 30, 2022, you can not use the standard password and must set up an App Password, click here for more details.

How the script works

1. The script ipChecker.sh first take the last know IP store in the ipHistory file.
2. It then pings the openDNS server to know which public IP address is assigned to the device.
   • If the two IPs are identical, nothing happen.
   • If the two IPs are different, the script send an email using the SMTP user configured in /etc/ssmtp/ssmtp.conf
3. The script will then store a timestamp and the new IP in the ipHistory file for logging purpose

Script setup

1. Edit the destination mail (line 11) the script will send the message to.
2. Edit the mail message (lines 25 to 30) the script will send. %s will be replaced by the new detected IP.
3. Change the ipHistory file location (line 10) if you want to give it another name or store it in another folder. The location can be relative to the script or an absolute path.

Additional steps

ipHistory

The ipHistory file must follow this format :

12-07-2022T13:20:02
1.2.3.4

The script will take the IP stored in the last line. For now, there is no limit to the space the file can take, so be careful.

Crontab

You can use crontab to launch the script regularly using :

crontab -e

For exemple, to launch the script every 15 minutes I use */15 * * * *, use crontab.guru to easily find the best setting for your usage.

TODO

• Limit the size of the ipHistory file by erasing older data