Logstash Installation error Fix : Unable to install system startup script for Logstash.

If you are also facing challenges while installing logstash version 6 or 7 with 

below bunch of dozen of error strings, you are at right place let's fix it.

Using provided startup.options file: /etc/logstash/startup.options
Exception in thread "main" java.lang.UnsupportedClassVersionError: org/jruby/Main : Unsupported major.minor version 52.0
        at java.lang.ClassLoader.findBootstrapClass(Native Method)
        at java.lang.ClassLoader.findBootstrapClassOrNull(ClassLoader.java:1078)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:419)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:417)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:323)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:363)
        at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482)
Unable to install system startup script for Logstash.
chmod: cannot access ‘/etc/default/logstash’: No such file or directory
warning: %post(logstash-1:7.5.2-1.noarch) scriptlet failed, exit status 1
Non-fatal POSTIN scriptlet failure in rpm package 1:logstash-7.5.2-1.noarch
  Verifying  : 1:logstash-7.5.2-1.noarch    

This error is mainly due to the existence of non supported version of java.

or these may be two versions of java installed within your system.

Logstash version 6+ has a dependency of Java 8+ , let know what is within our system and what's our default version picked up y CLI.

Run the below command to check java version.

# java -version

java version "1.7.0_231"
OpenJDK Runtime Environment (amzn-2.6.19.1.80.amzn1-x86_64 u231-b01)
OpenJDK 64-Bit Server VM (build 24.231-b01, mixed mode)

Verify it must be greater then 8, if not then uninstall the older version and install Java version 8.

# yum remove java-1.7.0-openjdk

# yum install java-1.8.0-openjdk

Verify the default version again and uninstall - install logstash again.
and finally run the below command.

# /usr/share/logstash/bin/system-install /etc/logstash/startup.options sysv