Start script on startup

Create your script

create your script with shebang on top

# myscript.sh
!#/bin/bash
echo "AAAAA"

Create service files

Create your myawesomeservice.service like /etc/systemd/system/myawesomeservice.service the .service and the end of file are required!

[Unit]
Description=Service desc.

[Service]
Type=simple
User=otheruser # not required just a note for me on how to run script as other user.
ExecStart=/bin/bash /path/to/my/script.sh

[Install]
WantedBy=multi-user.target

chmod and final command

chmod 644 /etc/systemd/system/myawesomeservice.service
systemctl enable myawesomeservice.service