Why do I get "security.Groups: Group mapping impl=org.apache.hadoop.security.ShellBasedUnixGroupsMapping; cacheTimeout=300000"?

$hdfs dfs -rmr crawl
    11/04/16 08:49:33 INFO security.Groups: Group mapping impl=org.apache.hadoop.security.ShellBasedUnixGroupsMapping; cacheTimeout=300000

I'm u开发者_如何学JAVAsing hadoop-0.21.0 with the default Single Node Setup configuration.

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It's not a warning, just a standard message. It shouldn't have been output at INFO level, however, because it does get printed with every message. In trunk it has been moved to DEBUG so you don't normally see it (in this JIRA). This will be incorporated into the next release.

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It's just an INFO what's your problem?