You can run the enable boot start command:
As root, run:
$SPLUNK_HOME/bin/splunk enable boot-start
To start splunk as another user, use -user parameter to specify which user to start Splunk as. For example, if Splunk runs as the user splunker, then as root you would run:
$SPLUNK_HOME/bin/splunk enable boot-start -user splunker
Thank you @the_wolverine for the well-written and accurate answer. This worked on CentOS 9 as well.
My only questions is why I found this in a user group instead of the install guide.
You can run the enable boot start command:
As root, run:
$SPLUNK_HOME/bin/splunk enable boot-start
To start splunk as another user, use -user parameter to specify which user to start Splunk as. For example, if Splunk runs as the user splunker, then as root you would run:
$SPLUNK_HOME/bin/splunk enable boot-start -user splunker