How to Start an application during boot without login in Linux-Yocto?

I am currently trying to deploy a yocto based image (which I built using bitbake core-image-minimal) on my raspberry pi 3 that would allow me to run a simple “helloworld” application after boot. I want my board to display the helloworld text without me needing to login with root id. I am using “systemd” and have already tried solutions such as appending the “-a root” command in systemd/serial-getty@service file to try and auto login but it isn’t working. Can anyone provide a solution for this?

You do not need to login to autostart the application. the startup procedure and scripts are following Debian:
You can either modify one of the existing scripts or create your own in /etc/init.d with symbolic link in /etc/rc5.d
Look at what we do for an FTP server:
ls -la /etc/rc5.d/
S80vsftpd -> …/init.d/vsftpd