Even in 2011, some of our internal applications still work on Oracle 9i.

I took liberty to attach a document prepared by Howard Rogers which gives detailed step-by-step instructions on installing oracle 9i on centos.

Eventhough the document is quite old ( written in 2006 )., it still holds good for CentOS 4.8.

Update: Feb 7th, 2011. For x86_64 based installs, the following additional steps have to be done.

1) Apart from the initial list of packages, install ‘glibc-devel.i386′. ( i.e., both glibc-devel.i386 and glibc-devel.x86-64 should be installed. ). Other compat packages to be installed are compat-gcc-32 compat-gcc-32-c++ compat-libgcc-296 compat-libstdc++-296.

2) Remove ‘compat-oracle-rhel4′ if it causes relinking issues.

source: http://forums.oracle.com/forums/thread.jspa?threadID=434407