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<sect><heading>Synchronizing Source Trees over the Internet<label id="synching"></heading>

<p><em>Contributed by &a.jkh;.</em>

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Last updated: $Date: 1997-08-18 00:03:59 $

This document tries to describe the various ways in which a user may
use the internet to keep development sources in synch.
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<p>There are various ways of using an Internet (or email) connection
to stay up-to-date with any given area of the FreeBSD project sources,
or all areas, depending on what interests you.  The primary
services we offer are CVSup and CTM.

<p><bf>CVSup</bf> uses the <em>pull</em> model of updating.  The
user (or a cron script) invokes the <tt>cvsup</tt> program, and it
interacts with a <tt>cvsupd</tt> server somewhere to bring your files
up to date.  The updates you receive are up-to-the-minute and you get
them when, and only when, you want them.  You can easily restrict your
updates to the specific files or directories that are of interest to
you.  Updates are generated on the fly by the server, according to
what you have and what you want to have.

<p><bf>CTM</bf>, on the other hand, does not interactively compare
the sources you have with those on the master archive.  Instead, a script
which identifies changes in files since its previous run is executed several
times a day on the master archive, any detected changes being compressed,
stamped with a sequence-number and encoded for transmission over email
(printable ASCII only).  Once received, these "CTM deltas" can then be
handed to the ctm_rmail(1) utility which will automatically decode, verify
and apply the changes to the user's copy of the sources.  This process is
far more efficient than CVSup, and places less strain on our server resources
since it is a <em>push</em> rather than a <em>pull</em> model.

<p>There are other trade-offs, of course.  If you
inadvertently wipe out portions of your archive, CVSup will detect
and rebuild the damaged portions for you.  CTM won't do this, and if
you wipe some portion of your source tree out (and don't have it backed
up) then you will have to start from scratch (from the most recent CVS
"base delta") and rebuild it all.

For more information on CTM and CVSup, please
see one of the following sections:

   &ctm;
   &cvsup;
