This reverts part of cacf9b6e34 (but also adds a "bind" option to the
remount command, as documented in mount(8)).
Apparently, doing "mount -o bind,ro" doesn't work. It outputs:
mount: warning: chroot/root/config seems to be mounted read-write.
and mounts read-write instead of read-only. This behaviour is
documented in mount(8). Newer kernels do seem to allow
combining bind with the read-only option (see mount(2)), but this does
not seem to work (possibly because mount is trying to be smart).
58209e8bd8