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.

Prerequisites

• 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.

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-1.8.0.252.b09-2.el7_8.x86_64/jre/bin/java)
*+ 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:

[datastax]
 name = DataStax Repo for Apache Cassandra
 baseurl = http://rpm.datastax.com/community
 enabled = 1
 gpgcheck = 0

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

cqlsh

The cqlsh interface should look similar to the image below:

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!