/ must be on a partition or LV that will be formatted. Reusing an existing / is not allowed.

[Stijn Hoop]

On Wed, 19 Oct 2011 07:51:40 -0400 (EDT)
Kamil Paral <kparal at redhat.com> wrote:
> > > I imagine this could be very inconvenient for me when switching
> > > distributions. I always have / and /home on the same partition. If
> > > I
> > > want hypothetically to go from let's say Ubuntu to Fedora, I
> > > delete all files except /home and then select that partition
> > > for /. If you force me to format that partition then I can't
> > > easily switch to Fedora, because my /home is huge and I have no
> > > external space to back
> > > it up.
> > 
> > Why not have /home as a separate partition? This is the classic
> > reason
> > for doing so. I mean, what you're doing in the above is basically
> > 'faking' a /home partition.
> > --
> > Adam Williamson
> 
> Because I never saw reason to do so. Having / and /home on the same
> partition saves you from problems with insufficient disk space in one
> place and too much space in the second place.

FWIW, this was exactly our reason too, especially a few years back when
disk space was relatively expensive compared to a Fedora install (ie 20
GB harddrives with 5 GB fedora -> 25%).

Nowadays there is much less reason not to have separate filesystems wrt
space, agreed. But it will cause some migration pain as we have a nice
system in place to preserve local user data. We will manage, but I just
wanted to state that there was a "valid" use case.

Regards,

--Stijn