CVSup 15.4 is now available

John Polstra jdp at
Tue Apr 28 16:27:04 PDT 1998

                     Announcing CVSup 15.4
Release 15.4 of CVSup, the CVS-aware network distribution system, is now

Where to Get CVSup
CVSup is free software.  It is available from:

and from all of the many FreeBSD FTP mirrors.  You can find a complete
list of them in the FreeBSD Handbook at:

CVSup is also available from the author's FTP server:

Please avoid this server if possible.  It has a rather slow link to
the Internet.

Full sources as well as FreeBSD binaries are available:

  cvsup-bin-15.4.tar.gz		FreeBSD static binaries for the client + GUI
  cvsup.nogui-bin-15.4.tar.gz	FreeBSD static binaries for the client (no GUI)
  cvsupd-bin-15.4.tar.gz	FreeBSD static binaries for the server
  cvsup-15.4.tar.gz		Sources **

The MD5 file signatures for these files are:

  MD5 (cvsup-bin-15.4.tar.gz) = aa4159387da988097ab5e7b5a164a93a
  MD5 (cvsup.nogui-bin-15.4.tar.gz) = 03b9f5013097437a34070b0abe8f3ba9
  MD5 (cvsupd-bin-15.4.tar.gz) = 5643802465ec683c3929d006bc95b5e9
  MD5 (cvsup-15.4.tar.gz) = 195b4b1cfb7db6d1fefbb4a9c9c27991

An updated port will appear in the FreeBSD ports and packages
collections soon:


  For FreeBSD-current:

  For FreeBSD-2.2:

If you want SOCKS support, you must also install the "modula-3-socks"
port or package:



SOCKS is supported only under FreeBSD, and only with dynamically linked
executables.  The static binary distributions do not support SOCKS.

** If you wish to build CVSup from the sources, be sure to read the
discussion further on in this announcement.

Why a New Release So Soon??
You may have noticed that this release comes rather soon after the
release of CVSup 15.3.  Unfortunately, around the same time that I
released 15.3, the maintainers of CVS released a new version of their
own software.  The new version of CVS introduced some unfortunate
changes in the whitespace conventions for the RCS files that it
generates.  CVSup updates RCS files by disassembling them on the
server, and putting the pieces back together again on the client.
The whitespace changes caused by the new version of CVS meant that
CVSup's reconstructed RCS files no longer matched the originals
exactly.  Logically, they were identical in every way; but differences
in the whitespace caused their MD5 checksums to disagree.  This led to
"fixups," which slowed down updates considerably.

To solve this problem once and for all, I have introduced a new
"loose" checksum in the current version.  It is used only for RCS
files.  It is essentially still an MD5 checksum of the file.  But it
carefully canonicalizes the white space, such that harmless white
space differences (an only the harmless ones) do not affect the
checksum.  Thus it checksums the meaning of the RCS file, rather than
the particular rendition of it.

For those who truly want their RCS files to be byte-for-byte identical
to those on the server, I have also added a couple of new supfile
keywords to help accomplish that, at some cost in update times.  See
the list of changes below and the man pages for details.

Compatibility with Previous Releases
This version is believed to interoperate properly with all earlier
public releases of CVSup.

What Has Changed Since the Previous Release?
  Implemented a "loose" checksumming algorithm for verifying updated
  RCS files.  The algorithm is still basically MD5, but it carefully
  ignores harmless differences (and only harmless differences) in
  white space.  Thus two RCS files which are logically the same will
  have identical checksums, even if they have meaningless differences
  in white space.  This change was made necessary by recent new
  versions of CVS, which introduced some gratuitous changes in the
  white space conventions for RCS files.  Since CVSup updates RCS
  files by disassembling them on the server and putting them together
  again on the client, the changes in the conventions for white space
  led to spurious checksum mismatches under the old, strict checksum.
  Note: Loose checksums require both the client and server to be at
  version 15.4 or later.  If either is older, then strict checksums
  are still used.

  Added a "strictrcs" supfile keyword, for those who don't trust the
  loose checksums.  It causes strict byte-by-byte checksums to be
  used for RCS files, as was the default in older versions of CVSup.

  Implemented a "nocheckrcs" keyword for client supfiles and server
  "releases" files, to suppress the comparison of MD5 checksums for
  updated RCS files entirely.  Given the new loose checksumming
  algorithm, this option is probably not very useful.

  Implemented a "norcs" keyword for client supfiles and server
  "releases" files, to disable the usual algorithm for updating RCS
  files.  If this keyword is specified, RCS files are treated the same
  as other kinds of files.  You can use this to force RCS files to be
  updated using the rsync algorithm, for instance.

  Fixed things up so that file names containing white space or other
  obnoxious characters no longer cause problems.  Also, when a release
  15.4 or later server or client is connected to an older peer, it is
  careful not to mention any files whose names contain white space.

What Is CVSup?
CVSup is a software package for distributing and updating collections
of files across a network.  CVSup is specifically tailored to
distributing CVS repositories.  By taking advantage of the special
properties of the files contained in CVS repositories, CVSup is
able to perform updates much faster than traditional systems.  It is
especially valuable for people with slow Internet connections.

CVSup parses and understands the RCS files making up a CVS repository.
When updates occur, CVSup extracts new deltas directly from the RCS
files on the server and edits them into the client's RCS files.
Likewise, CVSup notes the addition of new symbolic tags to the files
on the server and sends only the new tags to the client.

CVSup is able to merge new deltas and tags from the server with deltas
and tags added locally on the client machine.  This makes it possible
for the client to check local modifications into his repository
without their being obliterated by subsequent updates from the server.
Note: Although this feature is fully implemented in CVSup, it will
probably not be practical to use it until some small changes have been
made to CVS.

In addition to distributing the RCS files themselves, CVSup is able to
distribute specific checked-out versions.  The client can specify a
symbolic tag, a date, or both and CVSup will extract the appropriate
versions from the server's CVS repository.  Checked-out versions do
not need to be stored on the server since CVSup can extract any
version directly from the CVS repository.

If the client has an existing checked-out tree, CVSup will apply the
appropriate edits to update the tree or transform it into the
requested version.  Only the differences between the existing version
and the desired version are sent across the network.

To update non-RCS files, CVSup uses the highly efficient rsync
algorithm, developed by Andrew Tridgell and Paul Mackerras.

CVSup uses lightweight processes (threads) to implement a streaming
protocol across the network.  This completely eliminates the delays
associated with the lock-step, request-reply form of communication
used by many existing protocols, such as sup and NNTP.  Information
is transferred at the full available speed of the network in both
directions at once.  Network latency and server response delays
are rendered practically irrelevant.

CVSup uses the "zlib" compression package to optionally compress all
communications.  This provides an additional 65-75% compression, on
top of the diff-based compression already built into CVSup.

For efficiency, all processing is built into the CVSup package
itself.  Neither the client nor the server executes any other

For further information about how CVSup works, see the (somewhat out
of date) "Blurb" document in the CVSup distribution.

Using CVSup to Maintain FreeBSD Sources
CVSup servers are currently running at about 20 mirror sites around
the world.  For an up-to-date list of them, see:

Using CVSup, you can easily receive or update any of the standard
FreeBSD source releases, namely, "cvs", "current", and "stable".
The manual page for cvsup(1) describes how to do that.  For more detailed
instructions, see the section on CVSup in the FreeBSD Handbook:

Building CVSup from the Sources
CVSup is written in Modula-3, a modern, compiled, object-oriented
language.  Modula-3 integrates threads, exceptions, and garbage
collection, providing an ideal vehicle for this sort of application.
Without Modula-3, CVSup would almost certainly not exist today.

If you wish to build CVSup from the sources, you will first need
to install the free Modula-3 compiler and runtime libraries from
DEC SRC.  A port is available in the FreeBSD ports collection, in
"lang/modula-3".  The corresponding package is, of course, available
in the packages collection.

You will also need version 1.0.4 or later of the "zlib" library.
In FreeBSD-2.1.6 and later releases, this library has been incorporated
into the system sources, in "src/lib/libz".  Prior to that, a
FreeBSD port was available in "devel/libz" of the FreeBSD ports
collection.  For other sources of this library, see the "Install"
file.  Do not try to use versions earlier than 1.0.4.

To build the entire system from source under FreeBSD, simply type
"make" in the top-level directory.  (That's the directory that has
sub-directories named "client" and "server", among others.)  To
force the executables to be statically linked, set the environment
variable "M3FLAGS" to "-DSTATIC".  To build the client without the
GUI (e.g., if you don't have the X Window System installed on your
machine), set it to "-DNOGUI".  To do both of these things, set the
environment variable to "-DSTATIC -DNOGUI".

The Makefiles should work on any reasonable Unix system.  If you
have trouble with them, it is easy to build the components manually.
Simply chdir into each of the following subdirectories in the given
order and type "m3build":


To build statically linked executables, add "-DSTATIC" to each
"m3build" command.  To build the client without the GUI (e.g., if
you don't have the X Window System installed on your machine) add

Portability Issues
I intend for CVSup to be portable to most POSIX systems.  Earlier
releases have been run on a number of different platforms, including
FreeBSD, Linux, HP-UX, SunOS, Solaris, and DEC OSF/1 ALPHA.  In the
current release I have attempted to increase rather than decrease

Anybody who succeeds in porting CVSup to other systems is encouraged
to send his changes to <cvsup-bugs at>.  As long as the
changes are reasonably palatable, they will be incorporated into
future CVSup releases.

CVSup uses several POSIX-specific functions which may make it more
of an effort to port the package to non-POSIX systems such as Win32.
These functions include mmap, fork, syslog, stat, and chmod, among

Status of this Release
CVSup was first released publicly in August of 1996.  Since then
it has seen heavy use, and it has been quite stable.  Like all
software, though, it is not perfect.  Please be prepared to find
bugs -- without a doubt, there are some.  Please report bugs to
<cvsup-bugs at>.

John Polstra, <jdp at>

Copyright 1996-1998 John D. Polstra
$Id: Announce,v 1.37 1998/04/28 21:33:14 jdp Exp $

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