How to add special user into system

Hi there
I want to run custom application on my vyos which needs special user like -s/usr/sbin/nologin -d/etc/unbound. I found there is a way to run adduser everytime when I boot my instance. Is there some way I can add it into system when I build the iso? Thanks

Why don’t you run applications with containers? Currently LTS release VyOS 1.3.3 or VyOS 1.4 support containers already. You can give it a try.