# installing the java jdk via .tar.gz from java.oracle.com to a RHEL / CentOS / Oracle Linux environment – similar on Debian / Ubuntu

You have two download options for Redhat and clones for Oracle’s JDK.  You can download RPM’s and use the RHEL rpm command to install the Java RPMs – or you can download a java-version.tar.gz based file – which is a combination of tar and gzip.

This blog addresses the .tar.gz installation.

Why choose this installation?  In my mind it gives you more control allows a higher level of customization – location management especially.  Read on.

So if you downloaded jdk-8u181-linux-x64.tar.gz here is how you can install it.

cd /root/Downloads
cp -p jdk-8u181-linux-x64.tar.gz /opt
cd /opt
tar xvzf jdk-8u181-linux-x64.tar.gz
mv jdk1.8.0_181 jdk8

# after the unzip you  don't need the gzip anymore
rm jdk-8u181-linux-x64.tar.gz
# are there any other version of java installed that uses "alternatives"? A previous RPM install automatically adds to "alternatives"
# what is "alternatives" - manages multiple versions of a software image - use "man alternatives" for more info.  There is also a update-alternatives command similar on Debian / Ubuntu.

alternatives --config java

# install the java version you just installed into "alternatives" /opt/jdk - by doing an alternatives --install as below
# (debian is something like update-alternatives)
alternatives --install /usr/bin/java java /opt/jdk8/bin/java 1

# now using the config option on alternates - make this the preferred version
[root@x360 ~]# alternatives --config java

There are 3 programs which provide 'java'.

Selection Command
-----------------------------------------------
1 java-1.7.0-openjdk.x86_64 (/usr/lib/jvm/java-1.7.0-openjdk-1.7.0.181-2.6.14.8.0.1.el7_5.x86_64/jre/bin/java)
* 2 java-1.8.0-openjdk.x86_64 (/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.171-8.b10.el7_5.x86_64/jre/bin/java)
+ 3 /opt/jdk8/bin/java

Enter to keep the current selection[+], or type selection number: 3
[root@x360 ~]#

java -version

# then in the hadoop user (or whatever user) add the following to your /home/hadoop/.bash_profile
# setting up java with java_home and path

export JAVA_HOME=$(readlink -f /usr/bin/java | sed "s:/bin/java::")
export PATH=$PATH:$JAVA_HOME/bin:$JAVA_HOME/jre/bin

# source ~/.bash_profile 
# to check what you have done...
[hadoop@x360 ~]$ echo $JAVA_HOME
/opt/jdk8
use "alternatives" command to show which installed version of java is being used - RHEL and clone compatible command
alternatives --config java

[hadoop@single-node sbin]$ alternatives --config java

There are 2 programs which provide 'java'.

Selection Command
-----------------------------------------------
1 java-1.7.0-openjdk.x86_64 (/usr/lib/jvm/java-1.7.0-openjdk-1.7.0.191-2.6.15.4.el7_5.x86_64/jre/bin/java)
*+ 2 java-1.8.0-openjdk.x86_64 (/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.181-3.b13.el7_5.x86_64/jre/bin/java)

Enter to keep the current selection[+], or type selection number:

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