PsyncX is designed to let you effortlessly backup whichever folders or hard drives are important to you. To that end we work our hearts out to make sure that your expectations don't get disappointed.

PsyncX is a wrapper program for psync and crontab. That means that PsyncX uses an existing free Unix application written by Dan Kogai, psync and the ability to schedule jobs (known as cron in Unix) to allow you to schedule backups whenever you want. Hence the name PsyncX (yes, I know it isn't very original, but I thought it would be fairly easy to understand the connection :-)

Well, the easiest way to find out is to read the man page (Unix speak for manual) for psync:

man psync

But seeing as you are trying to figure out whether to install this or not, here is the gist of the man page:
psync does an update copy. It compares source directory and target directory at first, then erases items that are nonexistent on source directory if specified and finally copies everything on source directory. Items with the same modification date and (data fork) size remain untouched, saving time on operation.

What this means is that psync will do an entire copy of whatever you specify the first time. From then on, if you specify the same source directory and same target directory, it will only backup the files that have changed. Finally, unalike most Unix applications, psync will keep all resource forks and other Mac specific attributes for files (if you don't know what this means, don't worry about it, it is a GOOD thing :-)

This text is taken straight from Dan Kogai's website Go there for more info.

There are two methods to install this module. CPAN is easier and more recommended.

1. Install the Developer Tools if you have not done so already. This is needed to compile the perl module below. (Binary distribution may be available in future)
2. invoke CPAN shell via
   sudo perl -MCPAN -e shell
3. If this is your first time using CPAN module, It will ask you several questions, mainly about network. Answer them.
4. type
   

   install MacOSX::File

   And CPAN module will download, compile, test and install the module all for you.

If you have a problem using CPAN, you can still install it as follows.

tar zxvf MacOSX-File-x.xx.tar.gz
cd MacOSX-File-x.xx
perl Makefile.PL
make
make test
sudo make install
NOTE: the instructions above currently do NOT work for 10.3 "Panther". The easiest way to get psync installed on your system is to install PsyncX 2.1.1