Operation System (OS) Authentication is possible in Oracle as long as you created the correct settings:

$useradd -g oinstall julien

$password julien
New Unix password: 
Retype New Unix Password:

$sqlplus / as sysdba

SQL> create user ops$julien identified externally;    <- Adding OPS is important, to indicate that this user will be authenticated by the OS, as long as he can log into the OS and he is part of the group, he can connect to the database.
User Created;


SQL> grant connect to ops$julien;
Grant succeeded

$ su - julien

julien$ export ORACLE_HOME=/u01/app/oracle/11.2.0/dbhome_1
julien$ export ORACLE_SID=orcl

julien$ cd $ORACLE_HOME
julien$ cd bin
julien$ ./sqlplus /

SQL*Plus: Release 11.2.0.4 Production on Thu Jan 18 13:36:26 2018

Copyright (c) 1982, 2016, Oracle.  All rights reserved.


Connected to:
Oracle Database 12c Standard Edition Release 11.2.0.4 - 64bit Production

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