Default username and password for SQL*Plus in Ubuntu 14.04?

Question

I followed the instructions mentioned to install SQL*Plus from Oracle Instant Client and How to Install SQLPlus.

SQL*Plus is successfully installed on my system but I cannot login and use it. There is a similar question here and here, but it is does not solve my problem.

On googling, most sources said that we enter a password upon installation, but I was neither prompted nor displayed any password. (I can attach terminal screen shots if it is required)

Is there any way I can login and start using SQL*Plus? Is there any default username or password?

I am stuck here: sqlplus username/password@//dbhost:1521/SID

I need a valid username and password. scott/tiger was of no help.

sqlplus / as sysdba gives this -> ERROR: ORA-12162: TNS:net service name is incorrectly specified and prompts me to enter username and password which I don't have.

I originally asked this question on AskUbuntu feeling its more appropriate there. If this question does not belong here, please comment and I will remove it.

EDIT:

I executed these statements after reading from here:

ORACLE_HOME=/u01/oracle; export ORACLE_HOME

ORACLE_SID=asdb; export ORACLE_SID

Now, On executing sqlplus / as sysdba I get the error message ERROR: ORA-12545: Connect failed because target host or object does not exist

On executing sqlplus64 scott/tiger@//dbhost:1521/SID I get the error message ERROR: ORA-12154: TNS:could not resolve the connect identifier specified

Answer 1

It does not have anything to do with Ubuntu. When you enter sqlplus / as sysdba sqlplus tries to connect to the local database, which sid and oracle home should be specified by the environment variables ORACLE_SID and ORACLE_HOME. You, obviously, have not defined these variables.

All you need is to get the username, password, host name, where your database is located, port for the listener (the default port is 1521) and the Oracle SID. Then connect with sqlplus username/password@//dbhost:1521/SID. If you know the password for SYS user and have orapwSID file in the $ORACLE_HOME/dbs directory on the server side, you can connect with sys with the following command: sqlplus sys/password@//dbhost:1521/SID as sysdba.

Answer 2

moving everything into instant_client_11_* directory worked for me.