Comment 4 for bug 9217

We could add some Ubuntu-specific marker to an essential package for this
purpose...that seems like the only way to provide for completely reliable
autodetection, since anything else could be removed by the admin.

Adding lsb-release to base seems reasonable enough, though. It's a tiny package
with one script, one config file, and no dependencies. We wouldn't be able to
detect highly stripped-down systems, but they don't tend to dual-boot, either.