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orainstRoot.sh

The orainstRoot.sh script must be run as root as second last step of an Oracle installation.
This script is found in the ora inventory directory.
As far as I can tell, in a Linux environment, the following performed by this script 
#  /u01/app/oraInventory/orainstRoot.sh
Changing permissions of /u01/app/oraInventory.
Adding read,write permissions for group.
Removing read,write,execute permissions for world.

Changing groupname of /u01/app/oraInventory to oinstall.
The execution of the script is complete.
After running the script, the newest file in /etc is oraInst.loc: 
# ls -lt /etc/ | sed -n 2p
-rw-r--r--  1 root root     56 Dec 27 15:43 oraInst.loc
No differences: 
# diff /u01/app/oraInventory/oraInst.loc /etc/oraInst.loc
After running orainstRoot.sh, $ORACLE_HOME/root.sh must be run.

See also

MOS Note 1493121.1 (which indicates that the behavior of the script differs on a Solaris, HP or Linux Itanium environment)

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