I prepared short installation HOWTO for Redhat and it's clones (Oracle Enterprise Linux and Centos). Installation on first two of them was fine without significant problems but Centos needs couple of workarounds which are the reason why I created this article. In fact there is not problem with Centos as it is same as RHEL and OEL but as Centos is not certified operating system OUI and some scripts makes complications during installation process. You might say "Use certified distribution", but there are lot of Centos users which don't want to use other distribution (for example because of missing free updates) or they don't use some of Virtual machines for Oracle. But in fact some of certified distributions aren't fully supported by the new Database release. In case You are the Centos 5 user here are the fixes for successful installation of 11gR2:
1. Old good /etc/redhat-release and /etc/issue (Optional)
Solution which I posted years ago for 10gR1 release does not solve everything. Also modification of oraparam.ini (which was far better solution) does not solve anything. But to be sure apply this settings (backup /etc/redhat-release and /etc/issue before) change existing value to
Red Hat Enterprise Linux Server release 5 (Tikanga)
2. Install fake redhat-release RPM file
OUI checks for presence of redhat-release package and if it is missing then it will skip the prerequisites verification process. Unfortunatelly there is centos-release package installed on system (Don't uninstall it!). I created fake centos-fake.noarch.rpm RPM package to solve this issue. If you don't trust to my packages (I fully understand this) You can build your own package using this .spec file. Install downloaded (built) package:
rpm -i centos-fake.noarch.rpm
Don't worry about package name, after installation it will appear as "redhat-release" in RPM database.
3. Solve the "ADVM/ACFS is not supported" issue
This workaround solves Oracle Database 11g Release 2 Grid Infrastructure installation (neccessary for ASM or RAC). In fact ASMFS is not needed for for ASM but in case you want to test this new feature this workaround will help you. ASMFS feature is available only on Redhat and Oracle Enterprise Linux distribuion. So SUSE (SLES) is out of play at this moment (I won't speculate wh y it so but modules are provided for RH and OEL kernel only) so as You can see not all certified distributions are supported equally. During root.sh execution or ohasd initiation You could see one of these messages:
ADVM/ACFS is not supported on centos-release-5-4.el5.centos
ADVM/ACFS is not supported on centos-release-5-3.el5.centos
ADVM/ACFS is not supported on centos-release-5-2.el5.centos
ADVM/ACFS is not supported on centos-release-5-1.el5.centos
To workaround use this simple fix (I suggest to do it before GRID installation):
echo "redhat-release-5Server-5" > /tmp/.linux_release
To prevent deletion or modification of .linux_release file I suggest to set immunitable flag:
chattr +i /tmp/.linux_release
Note!: This workaround is working for Redhat clones (OEL, Centos) only! It will be not working on other distros.
Now your Centos will appear for Oracle 11g R2 as certified distribution. Full installation paper for all three distributions (including workarounds for Centos) You can find here or in menu of this page.