Fix wrong description for nova image-create

In the subsection "Create an image (nova)", there is a sentence said "You
cannot create a snapshot from an instance that has an attached volume",
which must be wrong. Currently, nova supports creating image from an
instance with attached volumes.

Change-Id: I811a845b8ee028ab83a12af03364930a0394e18d
Closes-Bug: #1341348

doc/common/section_cli_nova_manage_images.xml

@@ -1,25 +1,18 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<section xmlns="http://docbook.org/ns/docbook"
+<section xmlns="http://docbook.org/ns/docbook" xmlns:xi="http://www.w3.org/2001/XInclude"
-  xmlns:xi="http://www.w3.org/2001/XInclude"
+    xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0" xml:id="nova_manage_images">
-  xmlns:xlink="http://www.w3.org/1999/xlink"
-  version="5.0"
-  xml:id="nova_manage_images">
     <title>Create an image (nova)</title>
-    <para>You can use the <command>nova</command> client to take a snapshot of a
+    <para>You can use the <command>nova</command> client to take a snapshot of a running instance to
-        running instance to create an image.</para>
+        create an image.</para>
-    <para>To minimize the potential for data loss and ensure that you create an
+    <para>To minimize the potential for data loss and ensure that you create an accurate image, you
-        accurate image, you should shut down the instance before you take a
+        should shut down the instance before you take a snapshot.</para>
-        snapshot.</para>
-    <para>You cannot create a snapshot from an instance that has an attached
-        volume. Detach the volume, create the image, and remount the
-        volume.</para>
     <procedure>
         <step>
             <para>Write any buffered data to disk.</para>
-            <para>For more information, see <link xlink:href="http://docs.openstack.org/openstack-ops/content/snapshots.html"
+            <para>For more information, see <link
-                    >Taking Snapshots</link> in the
+                    xlink:href="http://docs.openstack.org/openstack-ops/content/snapshots.html"
-                    <citetitle>OpenStack Operations
+                    >Taking Snapshots</link> in the <citetitle>OpenStack Operations
-                Guide</citetitle>.</para>
+                    Guide</citetitle>.</para>
         </step>
         <step>
             <para>List instances to get the server name:</para>
@@ -29,13 +22,30 @@
 +--------------------------------------+----------------------+--------+------------+-------------+------------------+
 | 84c6e57d-a6b1-44b6-81eb-fcb36afd31b5 | myCirrosServer       | ACTIVE | None       | Running     | private=10.0.0.3 |
 +--------------------------------------+----------------------+--------+------------+-------------+------------------+</computeroutput></screen>
-            <para>In this example, the server is named
+            <para>In this example, the instance is named <literal>myCirrosServer</literal>.</para>
-                    <literal>myCirrosServer</literal>.</para></step>
+        </step>
-        <step><para>Use this server to create a snapshot:
+        <step>
-                <screen><prompt>$</prompt> <userinput>nova image-create myCirrosServer myCirrosImage</userinput></screen>The
+            <para>Use this instance to create a snapshot:</para>
-                command creates a qemu snapshot and automatically uploads the
+            <screen><prompt>$</prompt> <userinput>nova image-create myCirrosServer myCirrosImage</userinput></screen>
-                image to your repository. Only the tenant that creates the image
+            <para>The command creates a snapshot and automatically uploads the image to your
-                has access to it.</para>
+                repository.</para>
+            <note>
+                <para>For snapshots that you create from an instance that was booted from a
+                    volume:</para>
+                <itemizedlist>
+                    <listitem>
+                        <para>The snapshot is based on the volume that is attached to the instance
+                            through the Block Storage service.</para>
+                    </listitem>
+                    <listitem>
+                        <para>No data is uploaded to the Image Service.</para>
+                    </listitem>
+                    <listitem>
+                        <para>You can find information about the snapshot in the properties of the
+                            image.</para>
+                    </listitem>
+                </itemizedlist>
+            </note>
         </step>
         <step>
             <para>Get details for your image to check its status:</para>
@@ -73,15 +83,14 @@
 | metadata kernel_id                  | df430cc2-3406-4061-b635-a51c16e488ac |
 | metadata instance_type_ephemeral_gb | 0                                    |
 +-------------------------------------+--------------------------------------+</computeroutput></screen>
-            <para>The image status changes from
+            <para>The image status changes from <literal>SAVING</literal> to
-                    <literal>SAVING</literal> to
+                    <literal>ACTIVE</literal>. Only the tenant who creates the image has access to
-                    <literal>ACTIVE</literal>. Only the tenant who
+                it.</para>
-                creates the image has access to it.</para>
         </step>
     </procedure>
-            <para>To launch an instance from your image, include the image ID
+    <para>To launch an instance from your image, include the image ID and flavor ID, as in the
-        and flavor ID, as in the following example:</para>
+        following example:</para>
-            <screen><prompt>$</prompt> <userinput>nova boot newServer --image 7e5142af-1253-4634-bcc6-89482c5f2e8a \
+    <screen><prompt>$</prompt> <userinput>nova boot newServer --image 7e5142af-1253-4634-bcc6-89482c5f2e8a \
    --flavor 3</userinput>
 <?db-font-size 50%?><computeroutput>+-------------------------------------+--------------------------------------+
 | Property                            | Value                                |