diff --git a/CHANGES.txt b/CHANGES.txt
index a20b378ef8..de6f01c60a 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -443,6 +443,9 @@ Release 0.22.0 - Unreleased
     HADOOP-7244. Documentation change for updated configuration keys.
     (tomwhite via eli)
 
+    HADOOP-7189. Add ability to enable 'debug' property in JAAS configuration.
+    (Ted Yu via todd)
+
   OPTIMIZATIONS
 
     HADOOP-6884. Add LOG.isDebugEnabled() guard for each LOG.debug(..).
diff --git a/src/java/org/apache/hadoop/security/UserGroupInformation.java b/src/java/org/apache/hadoop/security/UserGroupInformation.java
index fc1c87ded9..0b00af7ce4 100644
--- a/src/java/org/apache/hadoop/security/UserGroupInformation.java
+++ b/src/java/org/apache/hadoop/security/UserGroupInformation.java
@@ -340,15 +340,24 @@ private static class HadoopConfiguration
       "hadoop-user-kerberos";
     private static final String KEYTAB_KERBEROS_CONFIG_NAME = 
       "hadoop-keytab-kerberos";
+
+    private static final Map<String, String> BASIC_JAAS_OPTIONS =
+      new HashMap<String,String>();
+    static {
+      String jaasEnvVar = System.getenv("HADOOP_JAAS_DEBUG");
+      if (jaasEnvVar != null && "true".equalsIgnoreCase(jaasEnvVar)) {
+        BASIC_JAAS_OPTIONS.put("debug", "true");
+      }
+    }
     
     private static final AppConfigurationEntry OS_SPECIFIC_LOGIN =
       new AppConfigurationEntry(OS_LOGIN_MODULE_NAME,
                                 LoginModuleControlFlag.REQUIRED,
-                                new HashMap<String,String>());
+                                BASIC_JAAS_OPTIONS);
     private static final AppConfigurationEntry HADOOP_LOGIN =
       new AppConfigurationEntry(HadoopLoginModule.class.getName(),
                                 LoginModuleControlFlag.REQUIRED,
-                                new HashMap<String,String>());
+                                BASIC_JAAS_OPTIONS);
     private static final Map<String,String> USER_KERBEROS_OPTIONS = 
       new HashMap<String,String>();
     static {
@@ -359,6 +368,7 @@ private static class HadoopConfiguration
       if (ticketCache != null) {
         USER_KERBEROS_OPTIONS.put("ticketCache", ticketCache);
       }
+      USER_KERBEROS_OPTIONS.putAll(BASIC_JAAS_OPTIONS);
     }
     private static final AppConfigurationEntry USER_KERBEROS_LOGIN =
       new AppConfigurationEntry(Krb5LoginModule.class.getName(),
@@ -371,6 +381,7 @@ private static class HadoopConfiguration
       KEYTAB_KERBEROS_OPTIONS.put("useKeyTab", "true");
       KEYTAB_KERBEROS_OPTIONS.put("storeKey", "true");
       KEYTAB_KERBEROS_OPTIONS.put("refreshKrb5Config", "true");
+      KEYTAB_KERBEROS_OPTIONS.putAll(BASIC_JAAS_OPTIONS);      
     }
     private static final AppConfigurationEntry KEYTAB_KERBEROS_LOGIN =
       new AppConfigurationEntry(Krb5LoginModule.class.getName(),