262 lines
11 KiB
XML
262 lines
11 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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version="5.0"
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xml:id="compute-service">
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<title>OpenStack Compute</title>
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<para>Use OpenStack Compute to host and manage cloud computing
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systems. OpenStack Compute is a major part of an
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Infrastructure-as-a-Service (IaaS) system. The main modules are
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implemented in Python.</para>
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<para>OpenStack Compute interacts with OpenStack Identity for
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authentication, OpenStack Image Service for disk and server
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images, and OpenStack dashboard for the user and administrative
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interface. Image access is limited by projects, and by users;
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quotas are limited per project (the number of instances, for
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example). OpenStack Compute can scale horizontally on standard
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hardware, and download images to launch instances.</para>
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<para>OpenStack Compute consists of the following areas and their
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components:</para>
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<variablelist>
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<title>API</title>
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<varlistentry>
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<term><systemitem class="service">nova-api
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service</systemitem></term>
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<listitem>
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<para>Accepts and responds to end user compute API calls. The
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service supports the OpenStack Compute API, the Amazon EC2
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API, and a special Admin API for privileged users to perform
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administrative actions. It enforces some policies and
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initiates most orchestration activities, such as running an
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instance.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="service">nova-api-metadata</systemitem>
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service</term>
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<listitem>
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<para>Accepts metadata requests from instances. The
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<systemitem class="service">nova-api-metadata</systemitem>
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service is generally used when you run in multi-host mode
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with <systemitem class="service">nova-network</systemitem>
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installations. For details, see <link
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xlink:href="http://docs.openstack.org/admin-guide-cloud/content/section_metadata-service.html"
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>Metadata service</link> in the <citetitle>OpenStack Cloud
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Administrator Guide</citetitle>.</para>
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<para>On Debian systems, it is included in the <systemitem
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class="service">nova-api</systemitem> package, and can be
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selected through <package>debconf</package>.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<variablelist>
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<title>Compute core</title>
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<varlistentry>
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<term><systemitem class="service">nova-compute</systemitem>
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service</term>
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<listitem>
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<para>A worker daemon that creates and terminates virtual
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machine instances through hypervisor APIs. For
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example:</para>
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<itemizedlist>
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<listitem>
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<para>XenAPI for XenServer/XCP</para>
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</listitem>
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<listitem>
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<para>libvirt for KVM or QEMU</para>
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</listitem>
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<listitem>
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<para>VMwareAPI for VMware</para>
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</listitem>
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</itemizedlist>
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<para>Processing is fairly complex. Basically, the daemon
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accepts actions from the queue and performs a series of
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system commands such as launching a KVM instance and
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updating its state in the database.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="service">nova-scheduler</systemitem>
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service</term>
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<listitem>
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<para>Takes a virtual machine instance request from the queue
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and determines on which compute server host it runs.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="service">nova-conductor</systemitem>
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module</term>
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<listitem>
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<para>Mediates interactions between the <systemitem
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class="service">nova-compute</systemitem> service and the
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database. It eliminates direct accesses to the cloud
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database made by the <systemitem class="service"
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>nova-compute</systemitem> service. The <systemitem
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class="service">nova-conductor</systemitem> module scales
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horizontally. However, do not deploy it on nodes where the
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<systemitem class="service">nova-compute</systemitem>
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service runs. For more information, see <link
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xlink:href="http://russellbryantnet.wordpress.com/2012/11/19/a-new-nova-service-nova-conductor/"
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>A new Nova service: nova-conductor</link>.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<variablelist>
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<title>Networking for VMs</title>
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<varlistentry>
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<term><systemitem class="service">nova-network</systemitem>
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worker daemon</term>
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<listitem>
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<para>Similar to the <systemitem class="service"
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>nova-compute</systemitem> service, accepts networking
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tasks from the queue and manipulates the network. Performs
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tasks such as setting up bridging interfaces or changing
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IPtables rules.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<?hard-pagebreak?>
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<variablelist>
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<title>Console interface</title>
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<varlistentry>
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<term><systemitem class="service">nova-consoleauth</systemitem>
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daemon</term>
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<listitem>
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<para>Authorizes tokens for users that console proxies
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provide. See <systemitem class="service"
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>nova-novncproxy</systemitem> and <systemitem
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class="service">nova-xvpnvcproxy</systemitem>. This
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service must be running for console proxies to work. You can
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run proxies of either type against a single <systemitem
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class="service">nova-consoleauth</systemitem> service in a
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cluster configuration. For information, see <link
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xlink:href="http://docs.openstack.org/trunk/config-reference/content/about-nova-consoleauth.html"
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>About nova-consoleauth</link>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="service">nova-novncproxy</systemitem>
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daemon</term>
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<listitem>
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<para>Provides a proxy for accessing running instances through
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a VNC connection. Supports browser-based novnc
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clients.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="service">nova-spicehtml5proxy</systemitem>
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daemon</term>
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<listitem>
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<para>Provides a proxy for accessing running instances through
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a SPICE connection. Supports browser-based HTML5
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client.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="service">nova-xvpnvncproxy</systemitem>
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daemon</term>
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<listitem>
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<para>Provides a proxy for accessing running instances through
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a VNC connection. Supports an OpenStack-specific Java
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client.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><systemitem class="service">nova-cert</systemitem>
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daemon</term>
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<listitem>
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<para>x509 certificates.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para os="debian">In Debian, a unique
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<package>nova-consoleproxy</package> package provides the
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<package>nova-novncproxy</package>,
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<package>nova-spicehtml5proxy</package>, and
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<package>nova-xvpvncproxy</package> packages. To select
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packages, edit the
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<filename>/etc/default/nova-consoleproxy</filename> file or use
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the <package>debconf</package> interface. You can also manually
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edit the <filename>/etc/default/nova-consoleproxy</filename> file,
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and stop and start the console daemons.</para>
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<variablelist>
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<title>Image management (EC2 scenario)</title>
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<varlistentry>
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<term><systemitem class="service">nova-objectstore</systemitem>
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daemon</term>
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<listitem>
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<para>An S3 interface for registering images with the
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OpenStack Image Service. Used primarily for installations
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that must support euca2ools. The euca2ools tools talk to
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<systemitem class="service">nova-objectstore</systemitem>
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in <emphasis role="italic">S3 language</emphasis>, and
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<systemitem class="service">nova-objectstore</systemitem>
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translates S3 requests into Image Service requests.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>euca2ools client</term>
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<listitem>
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<para>A set of command-line interpreter commands for managing
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cloud resources. Although it is not an OpenStack module, you
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can configure <systemitem class="service"
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>nova-api</systemitem> to support this EC2 interface. For
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more information, see the <link
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xlink:href="https://www.eucalyptus.com/docs/eucalyptus/3.4/index.html"
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>Eucalyptus 3.4 Documentation</link>.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<variablelist>
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<title>Command-line clients and other interfaces</title>
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<varlistentry>
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<term>nova client</term>
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<listitem>
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<para>Enables users to submit commands as a tenant
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administrator or end user.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<variablelist>
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<title>Other components</title>
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<varlistentry>
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<term>The queue</term>
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<listitem>
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<para>A central hub for passing messages between daemons.
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Usually implemented with <link
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xlink:href="http://www.rabbitmq.com/">RabbitMQ</link>, but
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can be implemented with an AMQP message queue, such as <link
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xlink:href="http://qpid.apache.org/">Apache Qpid</link> or
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<link xlink:href="http://www.zeromq.org/">Zero
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MQ</link>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>SQL database</term>
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<listitem>
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<para>Stores most build-time and run-time states for a cloud
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infrastructure, including:</para>
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<itemizedlist>
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<listitem>
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<para>Available instance types</para>
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</listitem>
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<listitem>
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<para>Instances in use</para>
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</listitem>
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<listitem>
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<para>Available networks</para>
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</listitem>
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<listitem>
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<para>Projects</para>
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</listitem>
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</itemizedlist>
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<para>Theoretically, OpenStack Compute can support any
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database that SQL-Alchemy supports. Common databases are
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SQLite3 for test and development work, MySQL, and
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PostgreSQL.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</section>
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