Disclaimer: Everything described here is a moving target and is subject to change.
It is assumed that for each user ${USER} there is a realm ${USER} located at /ix/realm/${USER}.
It is also assumed that this realm contains all the programs needed to operate and log in to the system.
An example of what you might find in a user realm: https://github.com/stal-ix/ix/blob/main/pkgs/set/pg/user/ix.sh