dcb8fa287e
Like documented at https://wiki.openstack.org/wiki/Documentation/Conventions#Client_arguments:_.22--option_ARGUMENT.22 we prefer to use '--option ARGUMENT'. Change-Id: If0a33ca02cd499769d1540b74b1ab0a217c839d4
248 lines
14 KiB
XML
248 lines
14 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE chapter [
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<!ENTITY % openstack SYSTEM "../common/entities/openstack.ent">
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%openstack;
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]>
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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="config-drive">
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<title>Store metadata on a configuration drive</title>
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<para>You can configure OpenStack to write metadata to a special
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configuration drive that attaches to the instance when it boots. The
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instance can mount this drive and read files from it to get information
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that is normally available through the <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>. This metadata is different from the user
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data.</para>
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<para>One use case for using the configuration drive is to pass a networking
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configuration when you do not use DHCP to assign IP addresses to
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instances. For example, you might pass the IP address configuration for
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the instance through the configuration drive, which the instance can
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mount and access before you configure the network settings for the
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instance.</para>
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<para>Any modern guest operating system that is capable of mounting an ISO
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9660 or VFAT file system can use the configuration drive.</para>
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<section xml:id="requirements">
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<title>Requirements and guidelines</title>
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<para>To use the configuration drive, you must follow the following
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requirements for the compute host and image.</para>
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<itemizedlist>
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<title>Compute host requirements</title>
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<listitem>
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<para>The following hypervisors support the configuration drive:
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libvirt, XenServer, Hyper-V, and VMware.</para>
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</listitem>
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<listitem>
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<para>To use configuration drive with libvirt, XenServer, or
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VMware, you must first install the
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<package>genisoimage</package> package on each compute
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host. Otherwise, instances do not boot properly.</para>
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<para>Use the <literal>mkisofs_cmd</literal> flag to
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set the path where you install the
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<package>genisoimage</package> program. If
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<package>genisoimage</package> is in same path
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as the <systemitem class="service"
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>nova-compute</systemitem> service, you do not
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need to set this flag.</para>
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</listitem>
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<listitem>
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<para>To use configuration drive with Hyper-V, you must set the
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<literal>mkisofs_cmd</literal> value to the full path to
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an <literal>mkisofs.exe</literal> installation.
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Additionally, you must set the
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<literal>qemu_img_cmd</literal> value in the
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<literal>hyperv</literal> configuration section to the
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full path to an <literal>qemu-img</literal> command
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installation.</para>
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</listitem>
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</itemizedlist>
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<itemizedlist>
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<title>Image requirements</title>
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<listitem>
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<para>An image built with a recent version of the
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<package>cloud-init</package> package can
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automatically access metadata passed through the
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configuration drive. The <package>cloud-init</package>
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package version 0.7.1 works with Ubuntu and Fedora based
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images, such as Red Hat Enterprise Linux.</para>
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</listitem>
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<listitem>
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<para>If an image does not have the
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<package>cloud-init</package> package installed, you
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must customize the image to run a script that mounts the
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configuration drive on boot, reads the data from the drive,
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and takes appropriate action such as adding the public key
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to an account. See <xref linkend="config_drive_contents"/>
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for details about how data is organized on the configuration
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drive.</para>
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</listitem>
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<listitem>
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<para>If you use Xen with a configuration drive, use
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the <literal>xenapi_disable_agent</literal>
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configuration parameter to disable the
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agent.</para>
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</listitem>
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</itemizedlist>
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<itemizedlist>
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<title>Guidelines</title>
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<listitem>
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<para>Do not rely on the presence of the EC2 metadata in the
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configuration drive, because this content might be removed
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in a future release. For example, do not rely on files in
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the <filename>ec2</filename> directory.</para>
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</listitem>
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<listitem>
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<para>When you create images that access configuration drive
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data and multiple directories are under the
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<filename>openstack</filename> directory, always select
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the highest API version by date that your consumer supports.
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For example, if your guest image supports the 2012-03-05,
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2012-08-05, and 2013-04-13 versions, try 2013-04-13 first
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and fall back to a previous version if 2013-04-13 is not
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present.</para>
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</listitem>
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</itemizedlist>
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</section>
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<section xml:id="enable_config_drive">
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<title>Enable and access the configuration drive</title>
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<procedure>
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<step>
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<para>To enable the configuration drive, pass the
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<literal>--config-drive true</literal>
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parameter to the <command>nova boot</command>
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command.</para>
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<para>The following example enables the configuration drive and
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passes user data, two files, and two key/value metadata
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pairs, all of which are accessible from the configuration
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drive:</para>
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<screen><prompt>$</prompt> <userinput>nova boot --config-drive true --image my-image-name --key-name mykey --flavor 1 --user-data ./my-user-data.txt myinstance --file /etc/network/interfaces=/home/myuser/instance-interfaces --file known_hosts=/home/myuser/.ssh/known_hosts --meta role=webservers --meta essential=false</userinput></screen>
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<para>You can also configure the Compute service to always
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create a configuration drive by setting the following option
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in the <filename>/etc/nova/nova.conf</filename> file:</para>
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<programlisting language="ini">force_config_drive=true</programlisting>
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<note>
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<para>If a user passes the
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<literal>--config-drive true</literal> flag to the
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<command>nova boot</command> command, an
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administrator cannot disable the configuration
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drive.</para>
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</note>
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</step>
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<step>
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<para>If your guest operating system supports accessing disk by
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label, you can mount the configuration drive as the
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<filename>/dev/disk/by-label/<replaceable>configurationDriveVolumeLabel</replaceable></filename>
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device. In the following example, the configuration drive
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has the <filename>config-2</filename> volume label.</para>
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<screen><prompt>#</prompt> <userinput>mkdir -p /mnt/config</userinput>
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<prompt>#</prompt> <userinput>mount /dev/disk/by-label/config-2 /mnt/config</userinput></screen>
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<note>
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<para>Ensure that you use at least version 0.3.1 of CirrOS
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for configuration drive support.</para>
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</note>
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<para>If your guest operating system does not use
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<literal>udev</literal>, the
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<filename>/dev/disk/by-label</filename>
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directory is not present.</para>
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<para>You can use the <command>blkid</command> command
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to identify the block device that corresponds to
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the configuration drive. For example, when you
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boot the CirrOS image with the
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<literal>m1.tiny</literal> flavor, the device
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is <filename>/dev/vdb</filename>:</para>
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<screen><prompt>#</prompt> <userinput>blkid -t LABEL="config-2" -odevice</userinput></screen>
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<screen><computeroutput>/dev/vdb</computeroutput></screen>
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<para>Once identified, you can mount the
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device:</para>
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<screen><prompt>#</prompt> <userinput>mkdir -p /mnt/config</userinput>
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<prompt>#</prompt> <userinput>mount /dev/vdb /mnt/config</userinput></screen>
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</step>
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</procedure>
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<simplesect xml:id="config_drive_contents">
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<title>Configuration drive contents</title>
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<para>In this example, the contents of the configuration drive are
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as follows:</para>
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<screen><computeroutput>ec2/2009-04-04/meta-data.json
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ec2/2009-04-04/user-data
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ec2/latest/meta-data.json
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ec2/latest/user-data
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openstack/2012-08-10/meta_data.json
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openstack/2012-08-10/user_data
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openstack/content
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openstack/content/0000
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openstack/content/0001
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openstack/latest/meta_data.json
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openstack/latest/user_data</computeroutput></screen>
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<para>The files that appear on the configuration drive
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depend on the arguments that you pass to the
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<command>nova boot</command> command.</para>
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</simplesect>
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<simplesect xml:id="os_metadata_format">
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<title>OpenStack metadata format</title>
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<para>The following example shows the contents of the
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<filename>openstack/2012-08-10/meta_data.json</filename> and
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<filename>openstack/latest/meta_data.json</filename> files.
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These files are identical. The file contents are formatted for
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readability.</para>
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<programlisting language="json"><xi:include parse="text" href="samples/meta_data.json"/></programlisting>
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<para>Note the effect of the <literal>--file
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/etc/network/interfaces=/home/myuser/instance-interfaces</literal>
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argument that was passed to the <command>nova
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boot</command> command. The contents of this file
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are contained in the
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<filename>openstack/content/0000</filename> file
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on the configuration drive, and the path is specified
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as <filename>/etc/network/interfaces</filename> in the
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<filename>meta_data.json</filename> file.</para>
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</simplesect>
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<simplesect xml:id="ec2_metadata_format">
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<title>EC2 metadata format</title>
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<para>The following example shows the contents of the
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<filename>ec2/2009-04-04/meta-data.json</filename> and the
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<filename>ec2/latest/meta-data.json</filename> files. These
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files are identical. The file contents are formatted to improve
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readability.</para>
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<programlisting language="json"><xi:include href="samples/meta_data_ec2.json" parse="text"/></programlisting>
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</simplesect>
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<simplesect xml:id="user_data">
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<title>User data</title>
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<para>The
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<filename>openstack/2012-08-10/user_data</filename>,
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<filename>openstack/latest/user_data</filename>,
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<filename>ec2/2009-04-04/user-data</filename>, and
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<filename>ec2/latest/user-data</filename> file are
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present only if the <literal>--user-data</literal>
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flag and the contents of the user data file are passed
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to the <command>nova boot</command> command.</para>
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</simplesect>
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<simplesect xml:id="config_drive_format">
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<title>Configuration drive format</title>
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<para>The default format of the configuration drive as an
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ISO 9660 file system. To explicitly specify the ISO
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9660 format, add the following line to the
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<filename>/etc/nova/nova.conf</filename>
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file:</para>
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<programlisting language="ini">config_drive_format=iso9660</programlisting>
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<para>By default, you cannot attach the configuration drive image as
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a CD drive instead of as a disk drive. To attach a CD drive, add
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the following line to the
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<filename>/etc/nova/nova.conf</filename> file:</para>
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<programlisting language="ini">config_drive_cdrom=true</programlisting>
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<para>For legacy reasons, you can configure the
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configuration drive to use VFAT format instead of ISO
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9660. It is unlikely that you would require VFAT
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format because ISO 9660 is widely supported across
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operating systems. However, to use the VFAT format,
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add the following line to the
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<filename>/etc/nova/nova.conf</filename>
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file:</para>
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<programlisting language="ini">config_drive_format=vfat</programlisting>
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<para>If you choose VFAT, the configuration drive is
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64 MB.</para>
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</simplesect>
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</section>
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</section>
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