Contributed by Jordan K. Hubbard
<jkh@FreeBSD.ORG>.
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 Anonymous CVS, CVSup and CTM.
Anonymous CVS and CVSup use the pull
model of updating sources. In the case of CVSup, the user
(or a cron script) invokes the cvsup program and it
interacts with a cvsupd 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. Anonymous CVS is
quite a bit more simplistic than CVSup in that it's just
an extention to cvs(1) which allows it to pull changes directly
from a remote CVS repository. CVSup can do this far more
efficiently, but anoncvs is easier to use.
CTM, on the other hand, does not interactively compare the sources you have with those on the master archive or otherwise pull changes across. Instead, a script which identifies changes in files since its previous run is executed several times a day on the master CTM machine, any detected changes being compressed, stamped with a sequence-number and encoded for transmission over email (in 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 or Anonymous CVS, and places less strain on our server resources since it is a push rather than a pull model.
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 anoncvs is probably more likely to become seriously confused than anything else. 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 with CTM or, with anoncvs, simply delete the bad bits and re-sync.
For more information on Anonymous CVS, CTM and CVSup, please see one of the following sections:
CTM?CTM?CTM for the first timeCTM in your daily lifeCTM