It is documented in the 12.04 release notes, and the installer has been adding this line automatically for years whenever static networking is selected at install time.
It's probably reasonable to also have it documented in interfaces(5), or at least a link provided to the resolvconf manpage, although I think it's unlikely that users will look there first when trying to debug why their nameserver entries have disappeared. That manpage belongs to the ifupdown package, so reassigning.
It is documented in the 12.04 release notes, and the installer has been adding this line automatically for years whenever static networking is selected at install time.
It's probably reasonable to also have it documented in interfaces(5), or at least a link provided to the resolvconf manpage, although I think it's unlikely that users will look there first when trying to debug why their nameserver entries have disappeared. That manpage belongs to the ifupdown package, so reassigning.