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 is the new kid on the block, it does everything that sup did and more, doing it also far more efficiently in terms of its demands on server disk space and network resources. Because of this, CVSup has largely replaced in the FreeBSD Project. Like sup, it also operates on a pull synchronization model.

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's a push rather than a pull model.

There are other trade-offs, of course. With CVSup, you can also inadvertently wipe out portions of your archive and 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, CVSup or the now largely-obsolete sup, please see one of the following sections: &ctm; &cvsup; ⊃