Comment 1 for bug 59547

It is quite hard to make sure that there is enough space, since the user could use several different mount points for his file system and we don't know how much space the installed packages requires in each directory.

The problem is that the packages are downloaded as root. And root is allowed to fill up the file system completely. We could only check if the package could be downloaded safely.

I will take a look at mvo's code in the dist-upgrade tool.