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Fix for Bug 7038: docs should mention metadata server specifics

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1 parent 417febf commit 0244cc5669cfb91267416bb09191d337d17f7291 @timf timf committed Jun 9, 2010
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  1. +109 −0 docs/src/faq.html
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109 docs/src/faq.html
@@ -37,6 +37,12 @@
<li>
<a href="#ec2-messaging">What EC2 operations are supported</a>?
</li>
+ <li>
+ <a href="#metadata-server">What is the metadata server</a>?
+ </li>
+ <li>
+ <a href="#metadata-fields">What metadata server operations are supported</a>?
+ </li>
<li>
<a href="#cloud-client">What is the cloud client</a>?
</li>
@@ -432,6 +438,109 @@
</div>
</li>
+ <li>
+ <p>
+ <a name="metadata-server"> </a>
+ <b>What is the metadata server? _NAMELINK(metadata-server)</b>
+ </p>
+
+ <p>
+ The metadata server responds to HTTP queries from VMs, using the same path names
+ as the <a href="http://docs.amazonwebservices.com/AWSEC2/latest/DeveloperGuide/index.html?AESDG-chapter-instancedata.html">EC2 metadata server</a>
+ </p>
+ <p>
+ The URL for this is obtained by looking at '<i>/var/nimbus-metadata-server-url</i>'
+ on the VM, which is an optional customization task injected by the Nimbus service
+ on your behalf (we are considering trying to simulate Amazon's hardcoded IP address
+ "169.254.169.254" on any subnet, feedback on this idea is appreciated).
+ </p>
+ <p>
+ Like on EC2, its responses are based on the source IP address from the TCP packet,
+ giving the information specific to each VM instance. This also means there is an
+ assumption that the immediately local network is non-spoofable. Administrators,
+ you should also put in place a firewall rule that restricts this port to the VMs
+ only, just in case.
+ </p>
+ <p>
+ The metadata server is disabled by default, consult your administrator (or try
+ a query from inside your VM).
+ </p>
+ <p>
+ Administrators, see "services/etc/nimbus/workspace-service/metadata.conf" for
+ the details.
+ </p>
+ </li>
+
+ <li>
+ <p>
+ <a name="metadata-fields"> </a>
+ <b>What metadata server fields are supported? _NAMELINK(metadata-fields)</b>
+ </p>
+
+ <p>
+ (See <a href="#metadata-server">What is the metadata server</a>?)
+ </p>
+ <p>
+ Nimbus provides a partial implementation of EC2's version of the metadata server
+ (<a href="http://docs.amazonwebservices.com/AWSEC2/latest/DeveloperGuide/index.html?instancedata-data-categories.html">their full field listing</a>).
+ These fields are currently supported:
+ </p>
+
+ <div class="uldonotmoveleft">
+ <ul>
+ <li>
+ <p>
+ <i>user-data</i> - "opaque" information injected by the client at
+ launch time
+ </p>
+ </li>
+ <li>
+ <p>
+ <i>meta-data/ami-id</i> - the ami-id assigned to this image. This
+ is simulated by the EC2 protocols in Nimbus, the "definitive" piece
+ of information for a launch is really the filename in the repository,
+ there is not AMI registry like on EC2.
+ </p>
+ </li>
+ <li>
+ <p>
+ <i>meta-data/ami-launch-index</i> - if this VM instance was launched
+ as part of a group (cluster), it might have a launch index other than
+ zero. This differentiates it from other homogenous nodes in the launch.
+ </p>
+ </li>
+ <li>
+ <p>
+ <i>meta-data/local-hostname</i> - the 'private' hostname of this VM [1]
+ </p>
+ </li>
+ <li>
+ <p>
+ <i>meta-data/local-ipv4</i> - the 'private' IP of this VM [1]
+ </p>
+ </li>
+ <li>
+ <p>
+ <i>meta-data/public-ipv4</i> - the 'public' hostname of this VM [1]
+ </p>
+ </li>
+ <li>
+ <p>
+ <i>meta-data/public-ipv4</i> - the 'public' IP of this VM [1]
+ </p>
+ </li>
+ </ul>
+
+ <p>
+ [1] - What 'public' and 'private' mean in this context is up to an
+ administrator configuration. The VM also may or may not have two NICs
+ on it, the values of these fields might be equal or not.
+ </p>
+
+ </div>
+ </li>
+
+
<li>
<p>
<a name="cloud-client"> </a>

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