When upgrading from Application Server 8.2 to 9.1 with the IFR installer on Linux platforms, selecting the Install JDK option, but after successful completion of the installation, most of the JES components stop working.
This issue only affects IFR installation of Application Server 9.1 in Linux platforms, and only when the Install JDK option is selected. To work around this issue, immediately after installation manually link /usr/jdk/entsys-j2se to the /usr/java/jdk1.5.0_12 directory.