Oracle 11g R2 on CentOS 6.3, and Net Configuration Assistant This is my first time installing Oracle 11g R2 on Linux. I followed all the instructions in the Oracle documentation, but in the installation process, the Net Configuration Manager is failed. I continued the process, and after it finished, I couldn't connect to sqlplus.

tnsnames.ora

# tnsnames.ora Network Configuration File: /Oracle/u01/app/oracle/product/11.2.0/db_1/network/admin/tnsnames.ora
# Generated by Oracle configuration tools.

ORCL =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = localhost.localdomain)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = orcl.localhost)
    )


listener.ora

# listener.ora Network Configuration File: /Oracle/u01/app/oracle/product/11.2.0/db_1/network/admin/listener.ora
# Generated by Oracle configuration tools.

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = localhost.localdomain)(PORT = 1521))
    )
  )

ADR_BASE_LISTENER = /Oracle/u01/app/oracle


Output of lsnrctl status

LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 29-MAR-2013 02:35:48

Copyright (c) 1991, 2009, Oracle.  All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=localhost.localdomain)(PORT=1521)))
TNS-12541: TNS:no listener
 TNS-12560: TNS:protocol adapter error
  TNS-00511: No listener
   Linux Error: 111: Connection refused


I used ./netca to reconfigure the listener, but the program told me that the port is in use. I deleted it and added a new one, but the same warning that port is in use. When I kill the process that uses this port (1521). and reconfigure the listener, the same message appears that the port is used.

When I run lsnrctl status, I get:


  Services Summary...
  Service "orcl.localhost" has 1 instance(s).
    Instance "orcl", status READY, has 1 handler(s) for this service...
  Service "orclXDB.localhost" has 1 instance(s).
    Instance "orcl", status READY, has 1 handler(s) for this service...  


But when I use sqlplus and enter user-name SYSTEM and its password, I get: 


  ERROR: ORA-12541: TNS:no listener
Community Wiki answer containing the solution originally added to the question by the author.

Finally I found the solution: I didn't change permission to be owned by the oracle user and oinstall group for the database dir in which the Oracle software is. I think there are some scripts or programs related to listener and the oracle user could not run it.