The value of env var SPLUNK_OS_USER, "splunk", does not match any user on this system;
This command can only be run by bootstart user.
WHAT I NEED TO RESOLVE IT?
When splunk is installed, a user should be created to run splunkd service. By default installation the user is "splunk", so in order to fix the issue, please create a user "splunk" in your environment.
On linux run:
chown -R splunk:splunk $SPLUNK_HOME
Check this document for further information -> https://docs.splunk.com/Documentation/Splunk/8.0.0/Installation/RunSplunkasadifferentornon-rootuser