With moving onto Ubuntu 22.04LTS, WCE triage needed to not use aufs anymore. Aufs is a union file system and it is around quite sometime, but apparently deprecated from 22.04.
I wrote a rather annoying script to do the file system overlay for 18.04, and continued to use it in 20.04. Here is the script.
So learning that aufs not available anymore, I was ready to rewrite it with overlayfs. After poking around with a lot of googling and reading man pages, I ran into overlayroot package.
I did not know I was solving a problem that I did not need to solve. It is already solved and all I have to do was to install this package and use it. Reading it, lt looks like it has been around quite sometime.
Sometimes, instead of solving the problem, the best way is to ask the right (google) question. Damn. I spent too much time on this.