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1. https://community.hortonworks.com/articles/14463/auth-to-local-rules-syntax.html

Public Interfaces

We extend the "sasl.kerberos.principal.to.local.rules"  format  config rule format by supporting  "/L" (toLowerCase) at the end of the rule. However, it must be noted that this does not affect how pattern matches on input and therefore that will still be case-sensitive.

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