using tnsnames.ora and sqlplus client without installing oracle 11g server on linux client
tnsnames.ora doesn't "come with" anything.  The key is not that file, as it is nothing but a names resolution file. And sqlplus is nothing but a CLI application. If you want to connect to an Oracle database (or ANY database) you must have, at a minimum, the client software for that particular database product. For oracle you need to download and install the Oracle client. The easiest would be the "instant client", which you can download from here: http://www.oracle.com/technetwork/database/features/instant-client/index-097480.html.  If you want the full "Admin" or "Runtime" client, download from edelivery.com and select just the client software. Pay attention to the license terms.