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Chapter 23. Creating Oracle User Accounts

To create the oracle account and groups, execute the following commands: 
su - root
groupadd dba          # group of users to be granted SYSDBA system privilege
groupadd oinstall     # group owner of Oracle files
useradd -c "Oracle software owner" -g oinstall -G dba oracle
passwd oracle
For more information on the "oinstall" group account, see when to use "OINSTALL" group during install of oracle.