In general, does a user have to log in to run a process and become its owner (ruid, or euid)? Does this apply to any user or any non-root user? For example:
In the boot sequence of Linux, the kernel starts the init system as the first process, and then the init process runs
loginso that each user can login. The init process is owned by
root, and does the user
roothave to log in before starting the
initprocess? See Why is there a `systemd` process owned by each user that is logged in?
sshto run a command without starting an interactive shell, do we have to log in first or not to run the command?