Comment 12 for bug 156177

As the description for this bug shows, there is no way to determine a size for /home and a size for / that will suitable for all users and will not cause problems for a large subset of users down the road.

The manner in which we've implemented the ubiquity-preserve-home specification does not involve creating a separate home partition. Instead, when the user chooses to install Ubuntu on a partition without formatting it, we remove all of the system files that will be replaced during installation (so everything but /home, /opt, etc), then proceed with a regular install. This is a much safer approach, and one that does not trouble many users with concepts like partitioning that they already find confusing.

Because we have purposefully chosen to not implement a separate /home partition option for the reasons stated above, I'm marking this bug invalid. Again, I'd just like to stress that the functionality exists, just not implemented in the manner that has been suggested here.

Thanks.