Thursday, 5 April 2007

PHP4 Running on RedHat Enterprise Linux 5

Stuart Herbert shows you how to get PHP4 running on RedHat Enterprise Linux 5. He informs you that RedHat’s newly released Enterprise Linux 5, which comes with version PHP 5.1.6. He had replaced this version with a copy of PHP4 built from source. He gives you the list of trials and errors that he had to face while installing PHP4.

After installing PHP4 he tried to start up Apache but it failed and showed an error. He says, the error has been triggered because the PHP runtime code contains text relocations, a situation where the code inside has to be writable in memory. He gives you a command to solve this issue.

But he found out that this command has its share of problems too. The first one is that it disables one of the protections that SELinux provides. It makes your server more vulnerable to security exploits targeted at the PHP runtime itself. The second problem is that your server uses more memory per Apache process, because each Apache process ends up with its own copy of PHP.

He gives two fixes to solve these problems. The first fix he suggests is to recompile your copy of PHP 4 using the ‘–with-pic’ configure option. This produces a copy of PHP that doesn’t contain text relocations. A second way to avoid text relocations is to use the prelink tool instead. This tool, run from the command-line, works out the text relocations once, and then writes the data back to the binaries and libraries, he initiates.