been searcing everywhere , i wanna know how to instaall, apache prefork module.or any documentation?

The prefork MPM should be enabled by default on unix / unix-like systems.

You can follow the compile and install instructions or install a package via the mechanism provided by whatever distro it is you are using...

thanks for answering, but I still dont understand what you mean,I read the page but dont understand, could you give an example plz.

Thanks

http://httpd.apache.org/docs/2.2/pro...iondirectories
" --with-mpm=MPM
Choose the process model for your server. You have to select exactly one
Multi-Processing Module. Otherwise the default MPM for your operating system
will be taken. Possible MPMs are beos, mpmt_os2, prefork, and worker. "
... > > --with-mpm=prefork
.....
http://httpd.apache.org/docs/2.0/mod/prefork.html
.....

http://packages.debian.org/lenny/apache2-mpm-prefork
" Apache HTTP Server - traditional non-threaded model

Each Apache Multi-Processing Module provides a different "flavor" of web server binary,
compiled with a different processing model.

The prefork MPM provides a non-threaded, pre-forking implementation that handles
requests in a manner similar to Apache 1.3. It is not as fast as threaded models,
but is considered to be more stable. It is appropriate for sites that need to maintain
compatibility with non-thread-safe libraries, and is the best MPM for isolating each
request, so that a problem with a single request will not affect any other. "
.....

thanks got it now, makes more sense....but what if apache is already installed with default mpm, how do I change it to prefork mpm? I would have to install apache over again?

Post the output of: # httpd -l

(that is a lowercase "L", not a number 1)

The prefork MPM probably already is the default in your case.