On Tue, 2013-12-17 at 19:10 -0800, W. Trevor King wrote:
> On Tue, Dec 17, 2013 at 05:07:26PM -0800, Brian Dolbec wrote:
> >  		if "SNAPCACHE" in self.settings:
> > -			self.mounts=["/proc","/dev","/usr/portage","/usr/portage/distfiles","/var/tmp/portage"]
> > -			self.mountmap={"/proc":"/proc","/dev":"/dev","devpts":"/dev/pts",
> > -				"/usr/portage":self.settings["snapshot_cache_path"]+"/portage",\
> > -				"/usr/portage/distfiles":self.settings["distdir"],"/var/tmp/portage":"tmpfs"}
> > +			self.mounts=["proc", "dev", "portdir", "distdir", "port_tmpdir"]
> > +			self.mountmap={"proc":"/proc", "dev":"/dev", "devpts":"/dev/pts",
> > +				"portdir":self.settings["snapshot_cache_path"]+"/portage",\
> > +				"distdir":self.settings["distdir"],"port_tmpdir":"tmpfs"}
> >  		else:
> >  			self.mounts = ["proc", "dev", "distdir", "port_tmpdir"]
> >  			self.mountmap = {"proc":"/proc", "dev":"/dev", "devpts":"/dev/pts",
> 
> Where does /usr/portage come from if SNAPCACHE is not enabled?  Is it
> just bind-mounted from the host's /usr/portage?
> 
> Cheers,
> Trevor
> 

It comes from the snapshot tarball created during a snapshot run.
SnapCache just keeps an unpacked copy ready to reuse.  That way it can
skip the unpack stage.