1. Install RHEL or CentOS . (on completion of installation dont forget to disable Firewall & SE linux)
2. Complete the prerequisites for 11G installation with Public OL yum repository as per following link.
http://www.oracle.com/technetwork/articles/servers-storage-admin/ginnydbinstallonlinux-488779.html
3. Edit /etc/hosts and add a fully qualified name for server like follows.
<IP-address> <fully-qualified-machine-name> <machine-name>
192.168.1.10 oratest.mydomain.com oratest
4. Set environment variable for bash shell like follows.
ORACLE_BASE=/oratest/app/oracle; export ORACLE_BASE
ORACLE_HOME=$ORACLE_BASE/product/11.2.0/dbhome_1; export ORACLE_HOME
ORACLE_SID=DBtest; export ORACLE_SID
PATH=/usr/sbin:$PATH; export PATH
PATH=$ORACLE_HOME/bin:$PATH; export PATH
LD_LIBRARY_PATH=$ORACLE_HOME/lib:/lib:/usr/lib; export LD_LIBRARY_PATH
CLASSPATH=$ORACLE_HOME/jlib:$ORACLE_HOME/rdbms/jlib; export CLASSPATH
5. Set the DISPLAY environment. DISPLAY=<machine-name>:0.0; export DISPLAY
6. Download RDBMS software from following link
http://www.oracle.com/technetwork/database/enterprise-edition/downloads/index.html
7. Once download complete unzip the files by unzip<filename>.zip
8. Goto OraDB11g/database (Extracted folder)
9. Make Directory for oracle software installation and give permission for same.
mkdir -p /disk1/DB
cd /disk1
chown -R oracle:oinstall /DB
This will start the installation.