We use to run java OpenJDK 6 on our servers, but the new version OpenJDK 7 is more secure and some of our customers have start requesting, so here are the instructions for installing and setting the correct variables.
For the previous post on installing OpenJDK 6 please see red5 installation.
Please note that it is possible to have on the same server both version OpenJDK 6 and OpenJDK 7.
First command, let us install OpenJDK:
yum install java-1.7.0-openjdk-devel
Linux Centos servers include a utility called
alternatives, which lets you change the default version for applications which allow multiple versions to be installed. OpenJDK is one such application.
alternativescommand is not installed by default, but may already be installed on your system. If not, install the
alternativespackage by running the following command:
# yum install alternatives
Issue the following command:
# /usr/sbin/alternatives --config java
the output could be something like:
# alternatives --config java There are 2 programs which provide 'java'. Selection Command ----------------------------------------------- 1 /usr/lib/jvm/jre-1.6.0-openjdk/bin/java 2 /usr/lib/jvm/jre-1.7.0-openjdk/bin/java Enter to keep the current selection[+], or type selection number: 2
if you type 2 the you selecting the OpenJDK 7.
and you can confirm by entering the command:
# java -version
the output should be something like:
[root@live ~]# java -version
java version “1.7.0_51”
OpenJDK Runtime Environment (rhel-220.127.116.11.el6_5-i386 u51-b02)
OpenJDK Client VM (build 24.45-b08, mixed mode, sharing)
Setup Environment Variables
Most of java based application’s uses environment variables to work. Use following commands to setup it.
# export JAVA_HOME=/usr/lib/jvm/jre-1.7.0-openjdk/bin/java
# export CLASSPATH=.:$JAVA_HOME/lib/classes.zip
Also export these variables in /etc/bashrc to become available for every user login or for any terminal opens.
# echo export JAVA_HOME=/usr/lib/jvm/jre-1.7.0-openjdk/bin/java >> /etc/bashrc
# echo export CLASSPATH=.:$JAVA_HOME/lib/classes.zip >> /etc/bashrc
Check if the variables are correct:
output should be:
[root@live ~]# echo $JAVA_HOME