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Linux Startup Script

Create a shell script that runs on startup

This is especially important for setting / resetting the permissions on devices such as GPS receivers

With the updated instructions of adding the web user www-data to the dialout group, this section is now moot for the purposed described above.

inspired by https://transang.me/create-startup-scripts-in-ubuntu/

1. Create a bash script file. In this example I will use it to reset permissions on a serial port. sudo nano /usr/local/bin/startup.sh

   #!/bin/bash
   FILE=/dev/ttyUSB0
   if [ -e "$FILE" ]; then
       echo "$FILE exists. GPS permissions will be set to 666"
       sudo chmod 666 /dev/ttyUSB0
   else
    echo -e "\e[1;41mWARNING: $FILE does not exist !!\e[1;m"
   fi
   

2. Set the permissions for this file to be executable: sudo chmod 744 /usr/local/bin/startup.sh.
3. test the script file: sudo startup.sh
4. create a .service file: sudo nano /etc/systemd/system/startup.service
5. add the following lines inside the file:

   [Unit]
   Description=Execute a script on system start
   After=network.target
      
   [Service]
   ExecStart=/usr/local/bin/startup.sh start
      
   [Install]
   WantedBy=multi-user.target
   

6. start and enable the daemon and check the status:

   sudo systemctl daemon-reload
   # then
   sudo systemctl enable startup.service
   sudo systemctl start startup.service