f004b3bc8f
Closes-Bug: 1295718 Author: Constanze Kratel <constanze.kratel@rackspace.com> Change-Id: I6e0461eb5cca3a5eff47a2ccabd0d1bf7a9a442d
98 lines
4.8 KiB
XML
98 lines
4.8 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE section [
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<!-- Some useful entities borrowed from HTML -->
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<!ENTITY ndash "–">
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<!ENTITY mdash "—">
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<!ENTITY hellip "…">
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<!ENTITY plusmn "±">
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<!-- Useful for describing APIs -->
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<!ENTITY GET '<command xmlns="http://docbook.org/ns/docbook">GET</command>'>
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<!ENTITY PUT '<command xmlns="http://docbook.org/ns/docbook">PUT</command>'>
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<!ENTITY POST '<command xmlns="http://docbook.org/ns/docbook">POST</command>'>
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<!ENTITY DELETE '<command xmlns="http://docbook.org/ns/docbook">DELETE</command>'>
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]>
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<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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xmlns:svg="http://www.w3.org/2000/svg"
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xmlns:m="http://www.w3.org/1998/Math/MathML"
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xmlns:html="http://www.w3.org/1999/xhtml"
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xmlns:db="http://docbook.org/ns/docbook" version="5.0"
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xml:id="concepts">
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<?dbhtml stop-chunking?>
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<title>Concepts</title>
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<para>To use the OpenStack Compute API effectively, you should
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understand several key concepts:</para>
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<itemizedlist>
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<listitem>
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<para><emphasis role="bold">Server</emphasis></para>
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<para>A virtual machine (VM) instance in the compute
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system. Flavor and image are requisite elements when
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creating a server.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Flavor</emphasis></para>
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<para>An available hardware configuration for a server.
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Each flavor has a unique combination of disk space,
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memory capacity and priority for CPU time.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Image</emphasis></para>
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<para>A collection of files used to create or rebuild a
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server. Operators provide a number of pre-built OS
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images by default. You may also create custom images
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from cloud servers you have launched. These custom
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images are useful for backup purposes or for producing
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“gold” server images if you plan to deploy a
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particular server configuration frequently.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Reboot</emphasis></para>
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<para>Use this function to perform either a soft or hard
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reboot of a server. With a soft reboot, the operating
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system is signaled to restart, which allows for a
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graceful shutdown of all processes. A hard reboot is
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the equivalent of power cycling the server. The
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virtualization platform should ensure that the reboot
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action has completed successfully even in cases in
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which the underlying domain/VM is paused or
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halted/stopped.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Rebuild</emphasis></para>
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<para>Use this function to remove all data on the server and
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replaces it with the specified image. Server ID and IP
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addresses remain the same.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Resize</emphasis></para>
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<para>Use this function to convert an existing server to a
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different flavor, in essence, scaling the server up or
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down. The original server is saved for a period of
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time to allow rollback if there is a problem. All
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resizes should be tested and explicitly confirmed, at
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which time the original server is removed. All resizes
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are automatically confirmed after 24 hours if you do
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not confirm or revert them.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Pause</emphasis></para>
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<para>You can pause a server by making a pause request. This
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request stores the state of the VM in RAM. A paused
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instance continues to run in a frozen state.</para>
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</listitem>
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<listitem>
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<para><emphasis role="bold">Suspend</emphasis></para>
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<para>Administrative users might want to suspend an
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instance if it is infrequently used or to perform
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system maintenance. When you suspend an instance, its
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VM state is stored on disk, all memory is written to
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disk, and the virtual machine is stopped. Suspending
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an instance is similar to placing a device in
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hibernation; memory and vCPUs become available to
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create other instances.</para>
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</listitem>
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</itemizedlist>
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</section>
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