After upgrading to Splunk 6.6, the splunkd.pid file is unreadable. How to fix "Permission denied" errors?

Hi Guys, I upgraded Splunk from 6.5 to 6.6 since then I'm unable to start Splunk properly, it seems there is some issue in the permission level. Could you walk me through in steps what I suppose to do to fix the permission denied error message pls? I'm just few months into Splunk so fairly new to everything. See the error message below: root@indexer:/opt/splunk/bin# ./splunk status Warning: cannot create "/opt/splunk/var/log/splunk" Warning: cannot create "/opt/splunk/var/log/introspection" Pid file "/opt/splunk/var/run/splunk/splunkd.pid" unreadable.: Permission denied Cannot initialize: /opt/splunk/etc/apps/Splunk_CiscoSecuritySuite/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/apps/launcher/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/apps/search/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/apps/splunk_instrumentation/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/system/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/apps/learned/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/apps/Splunk_CiscoSecuritySuite/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/apps/launcher/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/apps/search/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/apps/splunk_instrumentation/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/system/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/apps/learned/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/apps/Splunk_CiscoSecuritySuite/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/apps/launcher/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/apps/search/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/apps/splunk_instrumentation/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/system/metadata/local.meta: Permission denied Cannot initialize: /opt/splunk/etc/apps/learned/metadata/local.meta: Permission denied Pid file "/opt/splunk/var/run/splunk/splunkd.pid" unreadable.: Permission denied splunkd.pid file is unreadable. Pid file "/opt/splunk/var/run/splunk/splunkd.pid" unreadable.: Permission denied