The ORA-12541 error is telling you that the listener is not running. You can configure, create, and start/stop the listener all through Oracle's GUI tool, the Net Manager. On Linux, this utility is in $ORACLE_HOME/bin/netmgr.
Dig Deeper on Oracle database design and architecture
Have a question for an expert?
Please add a title for your question
Get answers from a TechTarget expert on whatever's puzzling you.