Synchronizing Source Trees over the Internet

Contributed by &a.jkh;.

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.

CVSup uses the pull model of updating. 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.

CTM, 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 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 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;