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From jgho...@apache.org
Subject svn commit: r951227 - in /hadoop/common/trunk: CHANGES.txt src/docs/src/documentation/content/xdocs/Superusers.xml src/docs/src/documentation/content/xdocs/site.xml
Date Fri, 04 Jun 2010 00:41:13 GMT
Author: jghoman
Date: Fri Jun  4 00:41:13 2010
New Revision: 951227

URL: http://svn.apache.org/viewvc?rev=951227&view=rev
HADOOP-6661. User document for UserGroupInformation.doAs. Contributed by Jitendra Pandey.


Modified: hadoop/common/trunk/CHANGES.txt
URL: http://svn.apache.org/viewvc/hadoop/common/trunk/CHANGES.txt?rev=951227&r1=951226&r2=951227&view=diff
--- hadoop/common/trunk/CHANGES.txt (original)
+++ hadoop/common/trunk/CHANGES.txt Fri Jun  4 00:41:13 2010
@@ -38,6 +38,9 @@ Trunk (unreleased changes)
     HADOOP-6714. Resolve compressed files using CodecFactory in FsShell::text.
     (Patrick Angeles via cdouglas)
+    HADOOP-6661. User document for UserGroupInformation.doAs. 
+    (Jitendra Pandey via jghoman)
     HADOOP-6638. try to relogin in a case of failed RPC connection (expired tgt) 
     only in case the subject is loginUser or proxyUgi.realUser. (boryas)

Added: hadoop/common/trunk/src/docs/src/documentation/content/xdocs/Superusers.xml
URL: http://svn.apache.org/viewvc/hadoop/common/trunk/src/docs/src/documentation/content/xdocs/Superusers.xml?rev=951227&view=auto
--- hadoop/common/trunk/src/docs/src/documentation/content/xdocs/Superusers.xml (added)
+++ hadoop/common/trunk/src/docs/src/documentation/content/xdocs/Superusers.xml Fri Jun  4
00:41:13 2010
@@ -0,0 +1,106 @@
+<?xml version="1.0"?>
+  Copyright 2002-2004 The Apache Software Foundation
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+      http://www.apache.org/licenses/LICENSE-2.0
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  See the License for the specific language governing permissions and
+  limitations under the License.
+<!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V2.0//EN"
+          "http://forrest.apache.org/dtd/document-v20.dtd">
+  <header>
+    <title> 
+      Superusers Acting On Behalf Of Other Users 
+    </title>
+  </header>
+  <body>
+    <section>
+      <title> Introduction </title>
+      <p>
+        This document describes how a superuser can submit jobs or access hdfs on behalf
of another user in a secured way.
+      </p>
+    </section>
+    <section> 
+      <title> Use Case  </title>
+        <p>
+          The code example described in the next section is applicable for the following
use case.
+        </p>
+        <p>
+          A superuser with username 'super' wants to submit job and access hdfs on behalf
of a user joe. The superuser has kerberos credentials but user joe doesn't have any. The tasks
are required to run as user joe and any file accesses on namenode are required to be done
as user joe. It is required that user joe can connect to the namenode or job tracker on a
connection authenticated with super's kerberos credentials. In other words super is impersonating
the user joe.
+       </p>
+     </section>
+      <section> 
+        <title> Code example  </title>
+        <p>
+             In this example super's kerberos credentials are used for login and a proxy
user ugi object is created for joe. The operations are performed within the doAs method of
this proxy user ugi object.
+        </p>
+        <source>
+             ...
+             //Create ugi for joe. The login user is 'super'.
+             UserGroupInformation ugi = 
+                     UserGroupInformation.createProxyUser("joe", UserGroupInformation.getLoginUser());
+             ugi.doAs(new PrivilegedExceptionAction&lt;Void&gt;() {
+               public Void run() throws Exception {
+                 //Submit a job
+                 JobClient jc = new JobClient(conf);
+                 jc.submitJob(conf);
+                 //OR access hdfs
+                 FileSystem fs = FileSystem.get(conf);
+                 fs.mkdir(someFilePath); 
+               }
+             }
+        </source>
+      </section>
+      <section> 
+        <title> Configurations </title>
+        <p>
+           The superuser must be configured on namenode and jobtracker to be allowed to impersonate
another user. Following configurations are required.
+        </p>
+           <source>
+             &lt;property&gt;
+               &lt;name&gt;hadoop.proxyuser.super.groups&lt;/name&gt;
+               &lt;value&gt;group1,group2&lt;/value&gt;
+               &lt;description&gt;Allow the superuser super to impersonate any members
of the group group1 and group2&lt;/description&gt;
+             &lt;/property&gt;
+             &lt;property&gt;
+               &lt;name&gt;hadoop.proxyuser.super.hosts&lt;/name&gt;
+               &lt;value&gt;host1,host2&lt;/value&gt;
+               &lt;description&gt;The superuser can connect only from host1 and host2
to impersonate a user&lt;/description&gt;
+             &lt;/property&gt;
+           </source>
+        <p>
+           If these configurations are not present, impersonation will not be allowed and
connection will fail.
+        </p>
+      </section>
+      <section> 
+        <title> Caveats </title>
+        <p>
+           The superuser must have kerberos credentials to be able to impersonate another
user. It cannot use delegation tokens for this feature. It would be wrong if superuser adds
its own delegation token to the proxy user ugi, as it will allow the proxy user to connect
to the service with the privileges of the superuser. 
+        </p>
+        <p>
+           However, if the superuser does want to give a delegation token to joe, it must
first impersonate joe and get a delegation token for joe, in the same way as the code example
above, and add it to the ugi of joe. In this way the delegation token will have the owner
as joe.
+        </p>
+      </section>
+  </body>

Modified: hadoop/common/trunk/src/docs/src/documentation/content/xdocs/site.xml
URL: http://svn.apache.org/viewvc/hadoop/common/trunk/src/docs/src/documentation/content/xdocs/site.xml?rev=951227&r1=951226&r2=951227&view=diff
--- hadoop/common/trunk/src/docs/src/documentation/content/xdocs/site.xml (original)
+++ hadoop/common/trunk/src/docs/src/documentation/content/xdocs/site.xml Fri Jun  4 00:41:13
@@ -42,6 +42,7 @@ See http://forrest.apache.org/docs/linki
 		<fsshell				        label="File System Shell"               href="file_system_shell.html"
 		<SLA					 	label="Service Level Authorization" 	href="service_level_auth.html"/>
 		<native_lib    				label="Native Libraries" 					href="native_libraries.html" />
+                <superusers                      label="Superusers Acting On Behalf Of
Other Users"     href="Superusers.html"/>
    <docs label="Miscellaneous"> 

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