hostname issues

I am still fighting with Portal Express installation. Now, I have changed my strategy and trying to install as silent with responsefile.

-silent
-G licenseAccepted="true"
-W setupTypePanel.selectedSetupTypeId="full"
-W globalInstall.location="/opt/IBM/WebSphere"
-W wasPanel.installChoice="install"

################################################################################
#
# EXISTING WEBSPHERE APPLICATION SERVER INSTALLATION LOCATION
#
# Description: This is the value of the existing WebSphere Application Server
# if you selected to install on an existing instance.
#
# Be sure to follow the convention for specifying path information on your
# platform. For example,
#
# Windows: C:\WebSphere\AppServer
# AIX: /usr/WebSphere/AppServer
# Linux: /opt/WebSphere/AppServer
# Solaris: /opt/WebSphere/AppServer
# iSeries ND: /QIBM/ProdData/WebSphere/AppServer/V7/ND
# iSeries Base: /QIBM/ProdData/WebSphere/AppServer/V7/Base
################################################################################

# -W wasListPanel.existingWasLocation=""

################################################################################
#
# OPTIONAL:
# UNDETECTED WEBSPHERE APPLICATION SERVER INSTALLATION LOCATION (NON-ISERIES)
#
# Description: Sometimes the Portal install program cannot detect an existing
# WebSphere Application Server(WAS). You cannot know this until install runtime
# when the silent install fails because the value of the above parameter
# wasListPanel.existingWasLocation cannot be validated.
#
# When this error occurs, and you are certain that there is a valid WAS at the
# location specified above, uncomment this parameter and enter the same value
# specified above.
#
# Be sure to follow the convention for specifying path information on your
# platform. For example,
#
# Windows: C:\WebSphere\AppServer
# AIX: /usr/WebSphere/AppServer
# Linux: /opt/WebSphere/AppServer
# Solaris: /opt/WebSphere/AppServer
#
################################################################################

# -W was.undetectedWas="/opt/IBM/WebSphere/AppServer"

and so on.
Now, as the responsefile expected, I have installed AppServer. I just wanted run and check, so called startServer.sh server1, to my surprise, it failed.
Stacktrace -
SystemErr R com.ibm.ws.exception.ConfigurationError:javax.naming.ConfigurationException: Cannot get canonical host name for server.

serverindex.xnl has hostname="null".
This is because -
Portal Server expected localhost.localdomain.com as hostname to localhost.localdomain.

I reverted /etc/hosts back to localhost.localdomain
and I have typed in hostname="localhost" in serverindex.xml.
Server started successfully.

Now, to kick start the PortalExpress, I am a kinda stuck, because, portal expects hostname as localhost.localdomain.com.
Portal cannot work with hostname as "localhost.localdomain.com", AppServer cannot run with host name *localhost.localdomain.com*. What a DEADLOCK!!!!!