You need to access Oracle database server from your linux machine, installed the Oracle client and you get the message above. Actually this is not the full message that you get, the full stuff is something like that:
$ /ora/fs0000/app/oracle/product/11.2/bin/sqlplus Error 6 initializing SQL*Plus SP2-0667: Message file sp1
.msb not found SP2-0750: You may need to set ORACLE_HOME to your Oracle software directory
So you start browsing the internet and people is asking you to check the msb files are actually there, that you got rights to read, some people will tell you that write rights are needed as well in some folders, etc.
This is not what is needed, after trying a lot of possible scenarios, the solution is as below:
1. You don't need any rights other than execute and read from the installed folders. That you have already.
2. Indeed the ORACLE_HOME must be set as follows
My fully qualified sqlplus path is /ora/fs0000/app/oracle/product/11.2/bin/sqlplus
For this to work you need to set the ORACLE_HOME as follows:
Before somebody told me to do so, I had tried already with other incorrect values. As soon as done as above, worked:
$ sqlplus SQL*Plus: Release 18.104.22.168.0 Production on Tue Apr 28 13:30:15 2015 Copyright (c) 1982, 2009, Oracle. All rights reserved. Enter user-name: