Today I expanded my root hammer fs by a second device. The expand went
flawless and except for some bogus numbers in df everything was fine.
Problems began when I rebooted the machine: I ended up in a unusable
system. I could not get mountroot to use the multi device hammer fs.
So we should either have (sorted by ascending coolness):
1) have a FAT warning in hammer man page to not expand the root file system
2) have hammer expand check and refuse to expand the root file system
3) have a mountroot that can handle multi device hammer fs roots.
Jan