useradd -u 200 -d /export/home/oracle -g oinstall -G dbadmin -m -s /bin/bash -c “RDBMS install user” oracle
Now, what does it mean?
-u = userid (it is convenient to keep this the same on multiple systems)
-d = home directory
-m = make the home directory if it doesn’t exist (believe me, it’s quite frustrating if you don’t (know) use this one.)
-s = which shell to use
-c = comment about the user
and at the end the user’s username.
source https://docs.sun.com/
UPDATE::
I noticed that the order in which the flags are given are important on version 11.2:
/usr/sbin/useradd -u 54321 -m -d /export/home/oracle -g oinstall -G dba,asmdba,backupdba,dgdba,kmdba -s /bin/bash -c “RDBMS install user” oracle
/usr/sbin/useradd -u 54322 -m -d /export/home/grid -g oinstall -G asmadmin,asmdba,dba -s /bin/bash -c “INFRASTRUCTURE install user” grid