I am experiencing the same issue after upgrading from ubuntu 17.04 to 17.10.
I then upgraded from splunk 6.6.3 to 6.6.5 hoping that this is resolve in this patch. IT IS NOT.
Did a fresh install of splunk 6.6.5, issues is still NOT RESOLVED.
Splunk> Now with more code!
Checking prerequisites...
Checking http port [8000]: open
Checking mgmt port [8089]: open
Checking appserver port [127.0.0.1:8065]: open
ERROR: pid 19180 terminated with signal 9
Checking kvstore port [8191]: open
Checking configuration... Done.
Creating: /opt/splunk/var/lib/splunk
Creating: /opt/splunk/var/run/splunk
Creating: /opt/splunk/var/run/splunk/appserver/i18n
Creating: /opt/splunk/var/run/splunk/appserver/modules/static/css
Creating: /opt/splunk/var/run/splunk/upload
Creating: /opt/splunk/var/spool/splunk
Creating: /opt/splunk/var/spool/dirmoncache
Creating: /opt/splunk/var/lib/splunk/authDb
Creating: /opt/splunk/var/lib/splunk/hashDb
New certs have been generated in '/opt/splunk/etc/auth'.
Checking critical directories... Done
ERROR: pid 19199 terminated with signal 9
Validating databases (splunkd validatedb) failed with code '-1'. If you cannot resolve the issue(s) above after consulting documentation, please file a case online at http://www.splunk.com/page/submit_issue
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