Silent Installation of FIx Pack for IBM HTTP Server Failing

I am trying to install Fix Pack 11 for IBM HTTP Server 8.5.5 on Linux. I am using a silent install. As a template, I used a response file that I had used on Windows. For some reason, Installation Manager thinks I'm trying to install IHS, instead of installing a Fix Pack for IHS:

stgpccggww3n01:/opt/IBM/InstallationManager/eclipse/tools# ./imcl -acceptLicense -showProgress input /home/devopsadm/WLP_IHS/update_WAS85_IHS_response.xml -log /home/devopsadm/WLP_IHS/update_WAS85_IHS.log
CRIMA1174E ERROR: The following errors were generated while installing.
CRIMA1174E ERROR:   There is already a package installed at "/opt/IBM/HTTPServer" in the "IBM HTTP Server V8.5" package group. The installation directory for the new "IBM HTTP Server for WebSphere Application Server V8.5" package group must not be the same as a previously used installation directory.

Here is my response file:

<?xml version="1.0" encoding="UTF-8"?>
<agent-input clean="false" temporary="true">
    <server>
        <repository location='/home/devopsadm/WLP_IHS/8.5.5-WS-WASSupplements-FP011'/>
    </server>
    <install modify='false'>
        <offering id='com.ibm.websphere.IHS.v85' 
                  profile='IBM HTTP Server for WebSphere Application Server V8.5' 
                  features='core.feature,arch.64bit'
                  installFixes='none'/>
    </install>
    <profile id='IBM HTTP Server for WebSphere Application Server V8.5' 
             installLocation='/opt/IBM/HTTPServer'>
        <data key='eclipseLocation' value='/opt/IBM/HTTPServer'/>
        <data key='user.import.profile' value='false'/>
        <data key='user.ihs.httpPort' value='80'/>
        <data key='user.ihs.http.server.service.name'
              value='IBM HTTP Server for WebSphere Application Server V8.5'/>
        <data key='user.ihs.installHttpService' value='false'/>
        <data key='user.ihs.http.server.service.name.key'
              value='IBMHTTPServerforWebSphereApplicationServerV8.5'/>
        <data key='user.ihs.win.serverServiceLogOnAsLocalSystem' value='false'/>
        <data key='user.ihs.win.serverServiceStartType' value='demand'/>
        <data key='user.ihs.win.serverServiceUser' value='Administrator'/>
        <data key='user.ihs.win.serverServicePassword' value='rvCInLaXB5kefhKxXzr3Jg=='/>
        <data key='cic.selector.nl' value='en'/>
    </profile>
</agent-input>

Does anyone have any idea why IIM thinks I'm installing a new version, as opposed to installing a fix pack?

Your input file's package group doesn't match the installed package group in the error message. Copy the one from the error message into the input file.

medium/long term I'd ditch the response file method and just use pure command-line. It's so much simpler.

I'd suggest playing with this under bash -x to see the very brief commands actually used to install or update.

https://github.com/covener/ihs-tools/blob/master/iminstallhelper.sh

This nets to the following after stashing a password in ~/iim.password:

# Show repo contents /opt/IM/eclipse/tools/imcl listAvailablePackages -repositories http://www.ibm.com/software/repositorymanager/V9WASSupplements -secureStorageFile $HOME/iim.storage -masterPasswordFile $HOME/iim.password -prompt

# Install IHS 9.0.0.0 + java (yes, space separated) /opt/IM/eclipse/tools/imcl install com.ibm.websphere.IHS.v90_9.0.0.20160526_1854 com.ibm.java.jdk.v8_8.0.4060.20170608_0739 -repositories http://www.ibm.com/software/repositorymanager/V9WASSupplements -installationDirectory /tmp/ihs9 -acceptLicense -secureStorageFile $HOME/iim.storage -masterPasswordFile $HOME/iim.password -showProgress

# Apply 9004 /opt/IM/eclipse/tools/imcl install com.ibm.websphere.IHS.v90_9.0.4.20170523_1327 -repositories http://www.ibm.com/software/repositorymanager/V9WASSupplements -installationDirectory /tmp/ihs9/ -acceptLicense -secureStorageFile $HOME/iim.storage -masterPasswordFile $HOME/iim.password