Novell LINUX ENTERPRISE SERVER 10 - INSTALLATION AND ADMINISTRATION 11-05-2007 Installation Manual page 744

WARNING: Risk of Data Loss
Before you start managing your data with a synchronization system, you should
be well acquainted with the program used and test its functionality. A backup
is indispensable for important files.
The time-consuming and error-prone task of manually synchronizing data can be
avoided by using one of the programs that use various methods to automate this job.
The following summaries are merely intended to convey a general understanding of
how these programs work and how they can be used. If you plan to use them, read the
program documentation.
39.1.1 CVS
CVS, which is mostly used for managing program source versions, offers the possibil-
ity to keep copies of the files on multiple computers. Accordingly, it is also suitable
for data synchronization. CVS maintains a central repository on the server in which the
files and changes to files are saved. Changes that are performed locally are committed
to the repository and can be retrieved from other computers by means of an update.
Both procedures must be initiated by the user.
CVS is very resilient to errors when changes occur on several computers. The changes
are merged and, if changes took place in the same lines, a conflict is reported. When a
conflict occurs, the database remains in a consistent state. The conflict is only visible
for resolution on the client host.
39.1.2 rsync
When no version control is needed but large directory structures need to be synchronized
over slow network connections, the tool rsync offers well-developed mechanisms for
transmitting only changes within files. This not only concerns text files, but also binary
files. To detect the differences between files, rsync subdivides the files into blocks and
computes checksums over them.
The effort put into the detection of the changes comes at a price. The systems to syn-
chronize should be scaled generously for the usage of rsync. RAM is especially impor-
tant.
726 Installation and Administration