bug#54666: Installation without non-root user accounts

[Ludovic Courtès]

Hello!

Using the installer, it’s possible to create a system config without any
non-root user accounts.  That’s a problem because then users end up
creating their account manually with ‘useradd’, which gets things wrong,
and things go awry.

To reproduce the issue, in the user page of the installer, add an
account for user “root”.  That’s enough to fool this check:

     (when (null? users)
       (run-error-page (G_ "Please create at least one user.")
                       (G_ "No user"))
       (run users))

This “root” account is then ignored:

  (define (users->configuration users)
    ;; …
    `((users (cons*
              ,@(filter-map (lambda (user)
                              ;; Do not emit a 'user-account' form for "root".
                              (and (not (string=? (user-name user) "root"))
                                   (user->sexp user)))
                            users)
              %base-user-accounts))))

… and that’s how you end up with a config without normal user accounts.

To address that, maybe ‘run-user-add-page’ should explicitly reject
“root”?

Ludo’.