export ALT_BOOTDIR="$JAVA_HOME": This var sets location of the bootstrap JDK. export ALT_MOZILLA_PATH=$PWD: This sets the variable that points to where you unzipped the Mozilla headers. export ALT_DEVTOOLS_PATH="/usr/bin": This changes the location where the build finds the needed executables. export BUILD_NUMBER="blfs-`date +%s`": This will help you identify this compiled version of the runtime environment and virtual machine by appending this information to the version in the output to java -version. export DEV_ONLY=true: This command eliminates compiling the documentation and eliminates a dependency for rpm. unset JAVA_HOME: This clears the JAVA_HOME variable as recommended by the build instructions. unset CLASSPATH: This clears the CLASSPATH variable as per the recommendations in the build instructions. unset CFLAGS...: These flags cause miscompilation of the build. Never set these. export INSANE=true: Unless you specify that you are insane the build will not proceed. The certified platform for the build is Redhat 6.1. The above variable ensures that all the errors related to compiling on a non-certified platform will be converted to warnings. export MAKE_VERBOSE=true: Allows the current compilation command to be displayed on the console. export ALT_CACERTS_FILE...: Specifies the certificate file to use.