Subject: Sup, FFS and checksums.
To: Michael L. Hitch <>
From: Shyeah right. What am I gonna do with a gun rack? <>
List: current-users
Date: 10/13/1995 09:28:23
I don't suppose there would be a way to implement a recursive checksumming
and byte-count procedure for the tree such that sup could just do a compare
between the master tree sumlist and the receiving host's sumlist and just
grab what appeared to be different?  Probably not atomic enough or some

On a related tangent (I seem to be going off on these lately...),
is there still an unused field in the inode of a FFS?  I can't help but
wonder that if there were perhaps a 'sum' flag on a file or collection of
files that when a close() or fsync() were effected, the file in question
would be checksummed and the value stored in some handy place if one
still exists.

It's probably too much to ask for, and it would definitely be a performance
hit which may not be acceptable for most people, but it would be nice to
be able to do this for a select set of files.  It would make sup's work
a bit easier in grabbing files which were truly different, to be sure.

[Does sup have a flag for doing a content comparison instead of just
 checking ctimes?  I appear to have blown away my manual page and, indeed,
 the sources for sup :-(]

Sun could have remained quite profitable by staying with BSD-based OSs, and
they wouldn't have pissed off NEARLY as many customers.