Install Oracle 10.2 64bit on CentOS 5 64bit

I'm installing Oracle on 64 bit CentOS in silent mode. After the installation, it says:

WARNING:The following configuration scripts /opt/oracle/product/10.2.0/root.s开发者_如何转开发h need to be executed as root for configuring the system.

But, when i execute root.sh as root, there're some errors. I found in the script it uses variables instead of plain command:

 if [ ! -d /var/tmp/.oracle ]
then
  **$MKDIR** -p /var/tmp/.oracle;
fi

**$CHMOD** 01777 /var/tmp/.oracle
**$CHOWN** root  /var/tmp/.oracle

and these variables are not defined. I don't know why it uses variables instead of the command itself.

You are aware that oracle is not certified/supported on centos?