MacPorts 2.3.2 and "port provides"

[Jan Stary]

On Oct 18 19:22:43, ryandesign at macports.org wrote:
> MacPorts should be in /opt/local, not /private/opt/local.
> Is it possible that /opt is a symlink to /private/opt? Ancient versions of the Cisco VPN installer were known to have moved /opt to /private/opt, then placed a symlink at /opt.

The /private thing seems to be a more general MacOS thing.
Sorry for the OT, but can someone please elaborate?

For example,

  $ vi /tmp/foo

creates "/tmp/foo" (obviously), but once I save it (:w),
it gets saved as "/private/tmp/foo"; at that moment,
there are two hardlinks for the same inode:

  $ ls -li /tmp/foo /private/tmp/foo 
  15307909 -rw-r--r--  1 hans  wheel  6 Mar  5 12:55 /private/tmp/foo
  15307909 -rw-r--r--  1 hans  wheel  6 Mar  5 12:55 /tmp/foo

Even after I finish editing it and exit vi (:wq),
these two names for the inode exist.

This is the system vi, which is /usr/bin/vi, on 10.5.8.
What is this /private directory for?

	Jan