How to Install OpenJDK 11 on CentOS 8

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What is OpenJDK?

openjdk logo

OpenJDk or Open Java Development Kit is a free, open-source framework of the Java Platform, Standard Edition (or Java SE). It contains the virtual machine, the Java Class Library, and the Java compiler. The difference between the Oracle OpenJDK and Oracle JDK is that OpenJDK is a source code reference point for the open-source model. Simultaneously, the Oracle JDK is a continuation or advanced model of the OpenJDK, which is not open source and requires a license to use.

In this article, we will be installing OpenJDK on Centos 8.


  • A Liquid Web core managed server running CentOS 8.
  • An account with root privileges
  • A root password set up on our system.
  • Access to a terminal window or an SSH command-line interface
[root@host2 ~]# cat /etc/redhat-release
CentOS Linux release 8.2.2004 (Core)
[root@host2 ~]#

Install OpenJDK 11

First, we want to locate the available versions of OpenJDK listed in the CentOS 8 repository using the following command.

[root@host2 ~]# dnf search jdk
Last metadata expiration check: 0:02:37 ago on Fri Aug 21 15:09:18 2020.
========== Name & Summary Matched: jdk ==========
java-11-openjdk-demo.x86_64 : OpenJDK Demos 11
java-1.8.0-openjdk-demo.x86_64 : OpenJDK Demos 8
java-11-openjdk-jmods.x86_64 : JMods for OpenJDK 11
java-11-openjdk-src.x86_64 : OpenJDK Source Bundle 11
java-1.8.0-openjdk-src.x86_64 : OpenJDK Source Bundle 8
java-11-openjdk.x86_64 : OpenJDK Runtime Environment 11
copy-jdk-configs.noarch : JDKs configuration files copier
java-1.8.0-openjdk.x86_64 : OpenJDK Runtime Environment 8
java-11-openjdk-javadoc.x86_64 : OpenJDK 11 API documentation
java-1.8.0-openjdk-javadoc.noarch : OpenJDK 8 API documentation
>>>java-11-openjdk-devel.x86_64 : OpenJDK Development Environment 11
java-1.8.0-openjdk-devel.x86_64 : OpenJDK Development Environment 8
java-11-openjdk-headless.x86_64 : OpenJDK Headless Runtime Environment 11
java-1.8.0-openjdk-accessibility.x86_64 : OpenJDK 8 accessibility connector
java-1.8.0-openjdk-headless.x86_64 : OpenJDK Headless Runtime Environment 8
java-11-openjdk-javadoc-zip.x86_64 : OpenJDK 11 API documentation compressed in single archive
java-1.8.0-openjdk-javadoc-zip.noarch : OpenJDK 8 API documentation compressed in single archive
========== Summary Matched: jdk ==========
jmc-core.noarch : Core API for JDK Mission Control
jmc.x86_64 : JDK Mission Control is a profiling and diagnostics tool
icedtea-web.noarch : Additional Java components for OpenJDK - Java browser plug-in and Web Start implementation
[root@host2 ~]#  
While we can run Java apps directly using the JRE, our apps will have to be compiled each time they are executed, which tends to be slower than running apps that have already been compiled. This would not be desirable if we plan to execute apps multiple times.

As you can see above, the version we want to install is:
java-11-openjdk-devel.x86_64 : OpenJDK Development Environment 11

To install this version, run the following command.

[root@host2 ~]# dnf install java-11-openjdk-devel.x86_64
Last metadata expiration check: 0:09:28 ago on Fri Aug 21 15:19:11 2020.
Dependencies resolved.
 Package Architecture Version Repository Size
 Java-11-openjdk-devel x86_64 1: system-AppStream 3.4 M

Installing dependencies:
Enabling module streams:
 javapackages-runtime 201801

Transaction Summary
Install 63 Packages

Total download size: 68 M
Installed size: 246 M
Is this ok [y/N]:   
Downloading Packages:
(1/63): cups-libs-2.2.6-33.el8.x86_64.rpm 15 MB/s | 432 kB 00:00
(2/63): glib-networking-2.56.1-1.1.el8.x86_64.rpm 9.9 MB/s | 155 kB 00:00
(3/63): gdk-pixbuf2-2.36.12-5.el8.x86_64.rpm 8.9 MB/s | 467 kB 00:00
Total 73 MB/s | 68 MB 00:00
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Running scriptlet: copy-jdk-configs-3.7-1.el8.noarch 1/1
  Running scriptlet: java-11-openjdk-headless-1: 1/1
Verifying : tzdata-java-2020a-1.el8.noarch 61/63
Verifying : xorg-x11-font-utils-1:7.5-40.el8.x86_64 62/63
Verifying : xorg-x11-fonts-Type1-7.5-19.el8.noarch 63/63
java-11-openjdk-1: java-11-openjdk-devel-1:
java-11-openjdk-headless-1: javapackages-filesystem-5.3.0-1.module_el8.0.0+11+5b8c10bd.noarch

[root@host2 ~]#

Verify Installation

Once the installation is completed, you can verify the installed Java version by running the following command.

[root@host2 ~]# java -version
openjdk version "11.0.8" 2020-07-14 LTS
OpenJDK Runtime Environment 18.9 (build 11.0.8+10-LTS)
OpenJDK 64-Bit Server VM 18.9 (build 11.0.8+10-LTS, mixed mode, sharing)
[root@host2 ~]# 

Since we have chosen the full installation of the OpenJDK development kit, we can check the compiler version as well.

[root@host2 ~]# javac -version
javac 11.0.8
[root@host2 ~]#

Install OpenJDK 8

Some Java apps only run on OpenJDK 8. If this is the case, we need to install OpenJDK 8. We can install OpenJDK 8 using the following command.

[root@host2 ~]# dnf install java-1.8.0-openjdk-devel.x86_64

Verify Installation

After installing this version of Java, we can check the version using the following command.

[root@host2 ~]# java -version
openjdk version "1.8.0_242"
OpenJDK Runtime Environment (build 1.8.0_242-b09)
OpenJDK 64-Bit Server VM (build 25.242-b09, mixed mode)
[root@host2 ~]#

Set Java Environment Variables

Now, we need to set the environmental variables for the new Java installations. This allows us to add both the JAVA_HOME and PATH settings, which will ensure that our Java applications can run without issue.

cat > /etc/profile.d/ <<EOF
export JAVA_HOME=\$(dirname \$(dirname \$(readlink \$(readlink \$(which javac)))))
export PATH=\$PATH:\$JAVA_HOME/bin
export CLASSPATH=.:\$JAVA_HOME/jre/lib:\$JAVA_HOME/lib:\$JAVA_HOME/lib/tools.jar

Next, we will source the file to begin using it without having to log out and log back in.

[root@host2 ~]# source /etc/profile.d/

To confirm the changes, run the following commands.

[root@host2 ~]# echo $JAVA_HOME

[root@host2 ~]# echo $PATH

If after installing both versions of Java by some chance show the following variables:

[root@host2 ~]# echo $JAVA_HOME

[root@host2 ~]# echo $PATH

and we wish to change the JAVA_HOME and PATH variables back to Java 11, run the following commands.

export JAVA_HOME=/usr/lib/jvm/java-11-openjdk-
export PATH=$PATH:$JRE_HOME/bin

We can also view the following folder location to see the full view of all the Java installations.

[root@host2 ~]# ll /usr/lib/jvm/
total 8
lrwxrwxrwx 1 root root 26 Aug 21 17:23 java -> /etc/alternatives/java_sdk
lrwxrwxrwx 1 root root 32 Aug 21 16:06 java-1.8.0 -> /etc/alternatives/java_sdk_1.8.0
lrwxrwxrwx 1 root root 40 Aug 21 16:06 java-1.8.0-openjdk -> /etc/alternatives/java_sdk_1.8.0_openjdk
drwxr-xr-x 7 root root 4096 Aug 21 16:06 java-1.8.0-openjdk-
lrwxrwxrwx 1 root root 29 Aug 21 15:49 java-11 -> /etc/alternatives/java_sdk_11
lrwxrwxrwx 1 root root 37 Aug 21 15:49 java-11-openjdk -> /etc/alternatives/java_sdk_11_openjdk
drwxr-xr-x 7 root root 4096 Aug 21 15:49 java-11-openjdk-
lrwxrwxrwx 1 root root 34 Aug 21 16:06 java-openjdk -> /etc/alternatives/java_sdk_openjdk
lrwxrwxrwx 1 root root 21 Aug 21 18:04 jre -> /etc/alternatives/jre
lrwxrwxrwx 1 root root 27 Aug 21 16:06 jre-1.8.0 -> /etc/alternatives/jre_1.8.0
lrwxrwxrwx 1 root root 35 Aug 21 16:06 jre-1.8.0-openjdk -> /etc/alternatives/jre_1.8.0_openjdk
lrwxrwxrwx 1 root root 51 Jul 16 11:10 jre-1.8.0-openjdk- -> java-1.8.0-openjdk-
lrwxrwxrwx 1 root root 24 Aug 21 15:49 jre-11 -> /etc/alternatives/jre_11
lrwxrwxrwx 1 root root 32 Aug 21 15:49 jre-11-openjdk -> /etc/alternatives/jre_11_openjdk
lrwxrwxrwx 1 root root 40 Jul 16 11:06 jre-11-openjdk- -> java-11-openjdk-
lrwxrwxrwx 1 root root 29 Aug 21 16:06 jre-openjdk -> /etc/alternatives/jre_openjdk
[root@host2 ~]# 

Change Java Versions

If we have several versions of Java installed, we can select an alternative if need be. To change versions, run the following command. 

[root@host2 ~]# alternatives --config java

There are 2 programs which provide 'java'.

  Selection Command
 + 1 java-11-openjdk.x86_64 (/usr/lib/jvm/java-11-openjdk-
* 2 java-1.8.0-openjdk.x86_64 (/usr/lib/jvm/java-1.8.0-openjdk-

Enter to keep the current selection[+], or type selection number: 1
[root@host2 ~]#   

In this case, we selected number 1, to keep the java-11-openjdk.x86_64 version. 


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Installing Tomcat 9 on Windows

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apache tomcat image
Apache Tomcat

What is Tomcat?

Apache Tomcat installs several Java Enterprise Edition specs including Java Servlet, JavaServer Pages, Java EL, and WebSocket. It provides for a “pure Java” HTTP web server environment in which Java code can run.

Tomcat 9 is the latest version of Apache’s Tomcat service and can easily be installed on Windows to serve as a convenient way to run Java.

There are many features and tools that Tomcat 9 has to offer that can make the deployment of web pages more manageable, including the use of JavaServer Pages.

Continue reading “Installing Tomcat 9 on Windows”

Install Java 8 on CentOS 7

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In this tutorial, we’ll be showing you how to install Oracle’s Java 8 programming language specifically onto a CentOS 7 server. This simple object-oriented language is used for many of the applications and websites you come across today.  Let’s jump right in!

Continue reading “Install Java 8 on CentOS 7”

How To Install Cassandra on CentOS 6

Reading Time: 3 minutes

Apache Cassandra is a NoSQL database intended for storing large amounts of data in a decentralized, high availability server cluster. NoSQL refers to a database with a data model other than the tabular relations used in relational databases such as MySQL, PostgreSQL, and Microsoft SQL.


  • These instructions are intended for installing Cassandra 2 on a single CentOS 6 node.
  • I’ll be working from a Liquid Web Core Managed CentOS 6.4 server, and I’ll be logged in as root.
  • You may be able to skip to Step #2 if you already have a stable version of Java 7 (preferably the Oracle/Sun JVM). Check to see if your server already has Java installed by running the following command: java -version

Step #1: Download Oracle Java SE Runtime Environment 8

Head over to Oracle’s website and download the latest version of Oracle Java SE Runtime Environment 8. Then, transfer the file up to your server into a directory of your choice. (We suggest using /usr/src/java8/ or something to that effect.

Following a licensing change of Oracle Java on 16 April 2019, Oracle now forbids anyone from downloading Java outside their approved process. That process is currently to log in to an Oracle account, accept the new license, then attempt the download with the authentication cookies in place. There are no known workarounds at this time.

Next, run the installation by using the command rpm -ivh <filename>, or in this case:

root@host [/usr/src/javaSE8]# rpm -ivh jre-8u251-linux-x64.rpm

Note: Your command may be slightly different if you downloaded a different version of Oracle Java SE Runtime Environment. Simply replace jre-xxxx-linux-x64.rpm with the actual filename.

Then install the Java Native Access (JNA) which can improve Cassandra’s memory usage:

yum install jna

Add a symbolic link to the Oracle Java SE Runtime Environment 8 installation so that your server uses the Oracle JRE instead of the OpenJDK JRE:

alternatives --install /usr/bin/java java /usr/java/jre1.8.0_45/bin/java 20000

Note: Your command will be slightly different if you downloaded a different version of Oracle Java SE Runtime Environment 8. Simply replace jrex.x.x_## with the actual version you’ve installed.

Then use the alternatives command to verify that the Oracle Java SE Runtime Environment 8 is selected. If not, simply choose the appropriate Selection after you run the command:

The results of your command should look similar to the information below:

root@host [/usr/src/javaSE8]# alternatives --config java

There is 1 program that provides 'java'.

  Selection    Command
+ 1           java-1.8.0-openjdk.x86_64 (/usr/lib/jvm/java-1.8.0-openjdk-
*+ 2           /usr/java/jre-8u251-linux-x64.rpm/bin/java
Enter to keep the current selection[+], or type selection number: 2
root@host [/usr/src/javaSE8]# java -version
java version "1.8.0_55"
Java(TM) SE Runtime Environment (build 1.8.0_55-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.55-b03, mixed mode)

Utilize the following command to double check the correct version of Oracle Java SE Runtime Environment 7 is being used:

java -version

Step #2: Add the DataStax Community Repository

For a refresher on editing files with vim see: New User Tutorial: Overview of the Vim Text Editor

vim /etc/yum.repos.d/datastax.repo

Add the following information to the file you’ve created, using i to insert:

 name = DataStax Repo for Apache Cassandra
 baseurl =
 enabled = 1
 gpgcheck = 0
How To Install Cassandra 2 and Run a Single Node Cluster on CentOS 6 - 02 DataStax Repo

Then exit and save the file with the command :wq (see the example below):

Step #3: Install Apache Cassandra 2

At this point, installing Cassandra is as simple as running just one command:

yum install dsc20

Step #4: Configure the Apache Cassandra 2 Environment

Just two more simple environment tweaks that enable Cassandra to run correctly:

export JAVA_HOME=/usr/java/jre1.7.0_45/
 export PATH=$PATH:/usr/java/jre1.7.0_45/bin/

Note: Your commands will be slightly different if you downloaded a different version of Oracle Java SE Runtime Environment 7. Simply replace jre1.7.0_45 with the actual version you’ve installed.

Step #5: Get Cassandra Running

Start-Up Cassandra

service cassandra start

Check Cassandra Service Status

service cassandra status

Enter the Cassandra Command Line


The cqlsh interface should look similar to the image below:

How To Install Cassandra 2 and Run a Single Node Cluster on CentOS 6 - 03 Cassandra Console

Check Cassandra Node Status

nodetool status

Shutdown Cassandra

service cassandra stop

There are many, many more things we could say about Cassandra, but those will be detailed in follow-up articles in the Liquid Web Knowledge Base! Look for articles on: How To Install Cassandra 2 and run a Multi-Node Server Cluster on CentOS 6, Recommended Production Settings for Cassandra on CentOS 6 and more!