Web authentication documentation is contradicting

Hi, I noticed recently folks are really focusing on documentation. (Kudos to +ajisakaa, +brahmareddy, +iwasakims, +daisuke.kobayashi, +jzhuge and more).

I've been following Hadoop documentation to set up web UI authentication, but it seems to be contradicting between docs, for example, for web UI Kerberos keytab settings:

• in Hadoop in Secure Mode (SecureMode.md), HDFS daemons have distinct web UI authentication configs, for example, for name node that's dfs.web.authentication.kerberos.keytab,
• but in Authentication for Hadoop HTTP web-consoles (HttpAuthentication.md), it mentions a Hadoop-wide config: hadoop.http.authentication.kerberos.keytab;
• finally, in Hadoop Auth, Java HTTP SPNEGO - Server Side Configuration(Configuration.md), it says{{[PREFIX.]kerberos.principal}} should be used.

They all seem to mean one thing, but different configuration names. So it's a bit of confusing, or even contradicting to each other. Can we improve it?