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I have the following setup (on multiple machines with RHEL7):


$ which java 
/usr/bin/java

$ ls -ltr /usr/bin/java 
/usr/bin/java -> /etc/alternatives/java

$ ls -ltr /etc/alternatives/java
/etc/alternatives/java -> /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.242b08-1.e17.x86_64/jre/bin/java

$ echo $JAVA_HOME
/etc/alternatives/jre_1.8.0_openjdk

$ ls -ltr /etc/alternatives/jre_1.8.0_openjdk
/etc/alternatives/jre_1.8.0_openjdk -> /usr/lib/jvm/jre-1.8.0-openjdk-1.8.0.242-1.e17.x86_64

I need to update to version 251 so I took the corresponding .tar.gz from artifactory , extract it in /usr/lib/jvm/jre-1.8.0-openjdk-1.8.0.251 and now I need to update all the simlink in order to use the latest java version.

Using the man pages of alternatives I did:

alternatives --install /usr/bin/java java /usr/lib/jvm/jre-1.8.0-openjdk-1.8.0.251/bin/java

Which modified /etc/alternatives/java but due to the fact that $JAVA_HOME=/etc/alternatives/jre_1.8.0_openjdk I need to modify/update /etc/alternatives/jre_1.8.0_openjdk .

I am not sure what to put as the <link> in alternatives --install <link> <name> <path> <priority> in order to update /etc/alternatives/jre_1.8.0_openjdk.

I'm not even sure that this is the correct approach towards updating java version . Thx

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  • You don't need to create any symlinks. All you need to do is prepend /usr/lib/jvm/jre-1.8.0-openjdk-1.8.0.251/bin to your PATH and /usr/lib/jvm/jre-1.8.0-openjdk-1.8.0.251/lib to your LD_LIBRARY_PATH and then set the JAVA_HOME` as /usr/lib/jvm/jre-1.8.0-openjdk-1.8.0.251. Commented Jul 14, 2020 at 2:21
  • You could also upgrade your RHEL systems, the current version of OpenJDK 8 in RHEL 7 is 262. Commented Jul 14, 2020 at 7:08

1 Answer 1

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This is the correct approach to hand-inserting an alternative in the alternatives system.

Your alternatives tool is a port of the original Debian update-alternatives tool. With that tool, and your port, there is 

update-alternatives --display jre_1.8.0_openjdk

which should tell you the "generic name" to use with --install. The vanilla Debian tool also has 

update-alternatives --query jre_1.8.0_openjdk
for a machine-readable form that can be used in pipelines, which your system does not have, however.

However: On RHEL, Java installations are installed with the --slave option to --install so that the JRE is switched in lockstep with the java program. In fact, there are between 20 and 50 --slave options that the install scripts for the packages set up. Witness the likes of this post-install script template for OpenJDK from AdoptOpenJDK (which isn't even setting up a JRE alternative, notice) for example.

Really this isn't something that you are going to be able to construct, error-free, longhand, to match what you already have. Don't download and install from raw TAR archives. Use the packages.

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