Comment 13 for bug 587186

Actually, the proper way to refuse to upgrade would be to follow what Debian did when they bumped the minimal platform requirement on SPARC. IIRC there was a preinst maintainer script segment that checked the machine type and exited dpkg with an error. Doing this would be the only totally foolproof method, since it cannot be assumed that someone will be using update-manager to upgrade. Instead they could very well use apt-get, aptitude other other tools, so foolproofing at the preinst level is the only truly safe option.