Run python script on raspberry pi 4 on startup/reboot

Dear People of Stackoverflow!

I am struggling to find a way to execute my python script on my Raspberry Pi4 on startup and reboot.

This would be a really basic Flask based API written in Python for manipulating a JSON Database with Post/Get HTTP requests.

I've already tried using crontab...

• The path to my API.py script is: /home/apiadmin/Deploy/API.py
• To the crontab file I've added the single line: @reboot python3 /home/apiadmin/API.py &

apiadmin supposed to be the root user

I can successfully safe the crontab file, upon rebooting and checking with crontab -l, the line is there.
However upon rebooting the Raspberry Pi the API is not reachable/script is not running

When I run it from PuTTY with the command: python3 /home/apiadmin/Deploy/API.py the script runs fine, and the API is on line, and every request works fine

Also I've tried using a launcher.sh, turning it to an executable but that fails saying it can't cd into the directory (same path) because it doesn't exist.

Also tried with a 30 second sleep to begin with... Didn't solve the problem.

Thank you in advance!

Lets use the systemd system and service manager, first we create a new service in /etc/systemd/system, something like sudo nano /etc/systemd/system/api.service

Then paste this inside, it contain the information about your API:

[Unit]
Description=My API Service
After=network.target

[Service]
ExecStart=/usr/bin/python3 /home/apiadmin/Deploy/API.py
WorkingDirectory=/home/apiadmin/Deploy
StandardOutput=inherit
StandardError=inherit
Restart=always
User=apiadmin

[Install]
WantedBy=multi-user.target

THen we save and give it the proper permissions sudo chmod 644 /etc/systemd/system/api.service.

Now if you want to start it just do sudo systemctl start api.service and if you want to start it it on boot sudo systemctl enable api.service