Hello friends,
I installed Oracle 10g R2 on CentOS 5.0. Now I was having problem starting the listener:

[oracle@nebuchadnezzar admin]$ lsnrctl start

LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 17-JUL-2007 00:14:52

Copyright (c) 1991, 2005, Oracle. All rights reserved.

Starting /mnt/work/oracle/product/10.2.0/db_1/bin/tnslsnr: please wait...

TNSLSNR for Linux: Version 10.2.0.1.0 - Production
System parameter file is /mnt/work/oracle/product/10.2.0/db_1/network/admin/listener.ora
Log messages written to /mnt/work/oracle/product/10.2.0/db_1/network/log/listener.log
Error listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC1)))
TNS-12555: TNSermission denied
TNS-12560: TNSrotocol adapter error
TNS-00525: Insufficient privilege for operation
Linux Error: 1: Operation not permitted

Listener failed to start. See the error message(s) above...

----------------------------------------------------------------------

As somebody suggested to me, I commented out the IPC line from my listener.ora and got the following result:

[oracle@nebuchadnezzar admin]$ lsnrctl start

LSNRCTL for Linux: Version 10.2.0.1.0 - Production on 17-JUL-2007 00:17:26

Copyright (c) 1991, 2005, Oracle. All rights reserved.

Starting /mnt/work/oracle/product/10.2.0/db_1/bin/tnslsnr: please wait...

TNSLSNR for Linux: Version 10.2.0.1.0 - Production
System parameter file is /mnt/work/oracle/product/10.2.0/db_1/network/admin/listener.ora
Log messages written to /mnt/work/oracle/product/10.2.0/db_1/network/log/listener.log
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=nebuchadnezzar)(PORT=1521)))

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=nebuchadnezzar)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 10.2.0.1.0 - Production
Start Date 17-JUL-2007 00:17:26
Uptime 0 days 0 hr. 0 min. 0 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /mnt/work/oracle/product/10.2.0/db_1/network/admin/listener.ora
Listener Log File /mnt/work/oracle/product/10.2.0/db_1/network/log/listener.log
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=nebuchadnezzar)(PORT=1521)))
Services Summary...
Service "PLSExtProc" has 1 instance(s).
Instance "PLSExtProc", status UNKNOWN, has 1 handler(s) for this service...
The command completed successfully
[oracle@nebuchadnezzar admin]$ dbstart
[oracle@nebuchadnezzar admin]$ sqlplus

SQL*Plus: Release 10.2.0.1.0 - Production on Tue Jul 17 00:18:00 2007

Copyright (c) 1982, 2005, Oracle. All rights reserved.

Enter user-name: scott/tiger
ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Linux Error: 2: No such file or directory

-------------------------------------------------------------------------------

My ORACLE_HOME and ORACLE_SID environment variables are set correctly.

I am stuck on this problem from many days, please help me out. I am posting my listener.ora, sqlnet.ora, tnsnames.ora and /etc/hosts files......

-----------------------------------------------
listener.ora:

SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(SID_NAME = PLSExtProc)
(ORACLE_HOME = /mnt/work/oracle/product/10.2.0/db_1)
(PROGRAM = extproc)
)
)

LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
# (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
(ADDRESS = (PROTOCOL = TCP)(HOST = nebuchadnezzar)(PORT = 1521))
)
)


sqlnet.ora:

NAMES.DIRECTORY_PATH= (TNSNAMES, EZCONNECT)


tnsnames.ora:

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

EXTPROC_CONNECTION_DATA =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
)
(CONNECT_DATA =
(SID = PLSExtProc)
(PRESENTATION = RO)
)
)


/etc/hosts:

127.0.0.1 nebuchadnezzar
-----------------------------------------------

Any help would be appreciated...

-Riz