“guix system container” script must run as root

[Ricardo Wurmus]

Hi Guix,

I see that the container script generated by “guix system container”
must be run as root.  Looking at “initialize-user-namespace” in (gnu
build linux-container) there is conditional code to be executed only
when running as an unprivileged user, namely writing to
/proc/pid/setgroups.  This makes me think that this was originally meant
to be usable without root privileges.

Without root privileges write access to /proc/pid/* is denied.  The
child process here is the result of issuing a clone syscall.

Why can’t the parent process write to the child’s /proc/pid/* files?
Why does the parent process need to do this at all?  Can’t the child
process take care of writing its /proc/self/uid_map?

-- 
Ricardo