Sample listener.ora file for Linux

Oracle Version: oracle 11g
Oracle SID: orcl
OS Version:- RHEL 6
Hostname:- server1.example.com
Server IP: 192.168.72.120


$ vi /u01/app/oracle/product/11.2.0/db_1/network/admin/listener.ora

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

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (GLOBAL_DBNAME = orcl)
      (ORACLE_HOME = /u01/app/oracle/product/11.2.0/db_1)
      (SID_NAME = orcl)
    )
  )

LISTENER =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = server1.example.com)(PORT = 1521))
  )

ADR_BASE_LISTENER = /u01/app/oracle