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<!ENTITY dhucpackage "<refentrytitle>ganeti-os-interface</refentrytitle>"> |
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<!ENTITY dhpackage "ganeti"> |
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<year>2006</year> |
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<year>2007</year> |
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<year>2008</year> |
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<year>2009</year> |
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<holder>Google Inc.</holder> |
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</copyright> |
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<refmiscinfo>ganeti 2.1</refmiscinfo> |
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</refmeta> |
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<refnamediv> |
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<refname>ganeti-os-interface</refname> |
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|
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<refpurpose>specifications for guest OS types |
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</refpurpose> |
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|
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</refnamediv> |
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|
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<refsect1> |
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<title>DESCRIPTION</title> |
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|
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<para> |
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The method of supporting guest operating systems in Ganeti is to |
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have, for each guest OS type, a directory containing a number of |
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required files. |
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</para> |
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|
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|
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</refsect1> |
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<refsect1> |
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<title>REFERENCE</title> |
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|
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<para> |
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There are six required files: <filename>create</filename>, |
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<filename>import</filename>, <filename>export</filename>, |
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<filename>rename</filename> (executables), |
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<filename>ganeti_api_version</filename> and |
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<filename>variants.list</filename> (text file). |
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</para> |
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|
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<refsect2> |
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<title>Common environment</title> |
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<para> |
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All commands will get their input via environment variables. A |
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common set of variables will be exported for all commands, and |
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some of them might have extra ones. Note that all counts are |
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zero-based. |
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</para> |
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<variablelist> |
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<varlistentry> |
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<term>OS_API_VERSION</term> |
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<listitem> |
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<simpara>The OS api version that the rest of the |
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environment conforms to.</simpara> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term>INSTANCE_NAME</term> |
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<listitem> |
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<simpara>The instance name the script should operate |
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on.</simpara> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term>INSTANCE_OS</term> |
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<listitem> |
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<simpara>The name os the instance's OS as Ganeti knows |
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it. This can simplify the OS scripts by providing the same |
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scripts under multiple names, and then the scripts can use |
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this name to alter their behaviour.</simpara> |
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<simpara>Under OS api 15 changing the script behavior based |
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on this variable is deprecated: OS_VARIANT should be used |
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instead (see below).</simpara> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term>OS_VARIANT</term> |
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<listitem> |
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<simpara>The variant of the OS which should be installed. Each OS |
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must support all variants listed under its |
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<filename>variants.list</filename> file, and may support more. |
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Any more supported variants should be properly documented in the |
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per-os documentation.</simpara> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term>HYPERVISOR</term> |
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<listitem> |
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<simpara>The hypervisor of this instance.</simpara> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term>DISK_COUNT</term> |
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<listitem> |
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<simpara>The number of disks the instance has. The actual |
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disk defitions are in a set of additional variables. The |
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instance's disk will be numbered from 0 to this value |
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minus one.</simpara> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term>DISK_%N_PATH</term> |
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<listitem> |
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<simpara>The path to the storage for disk N of the |
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instance. This might be either a block device or a regular |
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file, in which case the OS scripts should use |
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<emphasis>losetup</emphasis> (if they need to mount |
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it). E.g. the first disk of the instance might be exported |
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as <envar>DISK_0_PATH=/dev/drbd0</envar>.</simpara> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term>DISK_%N_ACCESS</term> |
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<listitem> |
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<simpara>This is how the hypervisor will export the |
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instance disks: either read-write (<emphasis>rw</emphasis>) or |
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read-only (<emphasis>ro</emphasis>).</simpara> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term>DISK_%N_FRONTEND_TYPE</term> |
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<listitem> |
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<simpara>(Optional) If applicable to the current |
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hypervisor type: the type of the device exported by the |
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hypervisor. For example, the Xen HVM hypervisor can export |
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disks as either <emphasis>paravirtual</emphasis> or |
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<emphasis>ioemu</emphasis>.</simpara> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term>DISK_%N_BACKEND_TYPE</term> |
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<listitem> |
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<simpara>How files are visible on the node side. This can |
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be either <emphasis>block</emphasis> (when using block |
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devices) or <emphasis>file:type</emphasis>, where |
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<emphasis>type</emphasis> is either |
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<emphasis>loop</emphasis> <emphasis>blktap</emphasis> |
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depending on how the hypervisor will be configured. Note |
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that not all backend types apply to all |
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hypervisors.</simpara> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term>NIC_COUNT</term> |
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<listitem> |
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<simpara>Similar to the <envar>DISK_COUNT</envar>, this |
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represents the number of NICs of the instance.</simpara> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term>NIC_%N_MAC</term> |
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<listitem> |
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<simpara>The MAC address associated with this |
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interface.</simpara> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term>NIC_%N_IP</term> |
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<listitem> |
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<simpara>The IP address, if any, associated with the N-th |
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NIC of the instance.</simpara> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term>NIC_%N_BRIDGE</term> |
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<listitem> |
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<simpara>The bridge to which this NIC will be attached |
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to.</simpara> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term>NIC_%N_FRONTEND_TYPE</term> |
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<listitem> |
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<para>(Optional) If applicable, the type of the exported |
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NIC to the instance, this can be one of of: <simplelist |
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type="inline"> <member>rtl8139</member> |
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<member>ne2k_pci</member> <member>ne2k_isa</member> |
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<member>paravirtual</member> </simplelist>. |
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</para> |
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</listitem> |
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</varlistentry> |
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<varlistentry> |
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<term>DEBUG_LEVEL</term> |
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<listitem> |
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<simpara>If non-zero, this should cause the OS script to |
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generate verbose logs of its execution, for |
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troubleshooting purposes. Currently only |
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<emphasis>0</emphasis> and <emphasis>1</emphasis> are |
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valid values.</simpara> |
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</listitem> |
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</varlistentry> |
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</variablelist> |
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</refsect2> |
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|
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<refsect2> |
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<title>create</title> |
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|
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<para>The <command>create</command> command is used for creating |
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a new instance from scratch. It has no additional environment |
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variables bside the common ones.</para> |
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|
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<para>The <envar>INSTANCE_NAME</envar> variable denotes the name |
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of the instance, which is guaranteed to resolve to an IP |
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address. The create script should configure the instance |
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according to this name. It can configure the IP statically or |
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not, depending on the deployment environment.</para> |
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|
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<para>The <envar>INSTANCE_REINSTALL</envar> variable is set to '1' when |
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this create request is reinstalling and existing instance, rather than |
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creating one anew. This can be used, for example, to preserve some |
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data in the old instance in an os-specific way.</para> |
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|
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</refsect2> |
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|
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<refsect2> |
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<title>export</title> |
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|
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<para> |
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This command is used in order to make a backup of a given disk |
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of the instance. The command should write to stdout a dump of |
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the given block device. The output of this program will be |
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passed during restore to the <command>import</command> |
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command. |
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</para> |
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|
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<para> |
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The specific disk to backup is denoted by two additional |
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environment variables: <envar>EXPORT_INDEX</envar> which |
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denotes the index in the instance disks structure (and could |
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be used for example to skip the second disk if not needed for |
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backup) and <envar>EXPORT_PATH</envar> which has the same |
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value as <emphasis>DISK_N_PATH</emphasis> but is duplicate |
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here for easier usage by shell scripts (rather than parse the |
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DISK_... variables). |
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</para> |
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|
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</refsect2> |
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|
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<refsect2> |
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<title>import</title> |
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|
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<para> |
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The <command>import</command> command is used for restoring an |
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instance from a backup as done by |
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<command>export</command>. The arguments are the similar to |
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those passed to <command>export</command>, whose output will |
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be provided on <acronym>stdin</acronym>. |
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</para> |
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|
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<para> |
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The difference in variables is that the current disk is called |
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by <envar>IMPORT_DEVICE</envar> and <envar>IMPORT_IDX</envar> |
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(instead of <emphasis>EXPORT_</emphasis>). |
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</para> |
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|
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</refsect2> |
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|
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<refsect2> |
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<title>rename</title> |
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|
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<para> |
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This command is used in order to perform a rename at the |
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instance OS level, after the instance has been renamed in |
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Ganeti. The command should do whatever steps are required to |
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ensure that the instance is updated to use the new name, if |
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the operating system supports it. |
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</para> |
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|
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<para> |
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Note that it is acceptable for the rename script to do nothing |
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at all, however be warned that in this case, there will be a |
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desynchronization between what <computeroutput>gnt-instance |
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list</computeroutput> shows you and the actual hostname of the |
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instance. |
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</para> |
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|
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<para>The script will be passed one additional environment |
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variable called <envar>OLD_INSTANCE_NAME</envar> which holds the |
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old instance name. The <envar>INSTANCE_NAME</envar> variable |
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holds the new instance name.</para> |
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|
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<para> |
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A very simple rename script should at least change the |
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hostname and IP address of the instance, leaving the |
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administrator to update the other services. |
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</para> |
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</refsect2> |
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|
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<refsect2> |
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<title>ganeti_api_version</title> |
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<para> |
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The <filename>ganeti_api_version</filename> file is a plain |
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text file containing the version(s) of the guest OS api that |
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this OS definition complies with, one per line. The version |
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documented by this man page is 15, so this file must contain |
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the number 15 followed by a newline if only this version is |
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supported. A script compatible more than one ganeti version |
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should contain the most recent version first (i.e. 15), |
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followed by the old version(s) (in this case 10 and/or 5). |
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</para> |
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</refsect2> |
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|
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<refsect2> |
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<title>variants.list</title> |
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<para> |
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<filename>variants.list</filename> is a plain text file |
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containing all the declared supported variants for this |
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OS, one per line. At least one variant must be supported. |
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</para> |
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</refsect2> |
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|
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</refsect1> |
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|
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<refsect1> |
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<title>NOTES</title> |
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|
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<refsect2> |
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<title>Retrocompatibility</title> |
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|
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<para> |
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Ganeti 2.1 is compatible with both api version 10, and 15. |
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In api version 10 the <filename>variants.list</filename> |
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file is ignored and no OS_VARIANT environment variable is |
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passed. |
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</para> |
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</refsect2> |
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|
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<refsect2> |
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<title>Common behaviour</title> |
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|
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<para>All the scripts should display an usage message when |
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called with a wrong number of arguments or when the first |
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argument is <option>-h</option> or |
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<option>--help</option>.</para> |
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|
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</refsect2> |
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|
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<refsect2> |
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<title>Upgrading from old versions</title> |
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<refsect3> |
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|
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<title>Version 10 to 15</title> |
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|
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<para> |
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The <filename>variants.list</filename> file has been |
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added, so OSes should support at least one variant, |
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declaring it in that file and must be prepared to parse |
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the OS_VARIANT environment variable. OSes are free to |
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support more variants than just the declared ones. |
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</para> |
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|
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</refsect3> |
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|
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<refsect3> |
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|
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<title>Version 5 to 10</title> |
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|
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<para> |
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The method os passing data has changed from command line |
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options to environment variables, so scripts should be |
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modified to use these. For an example of how this can be |
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done in a way compatible with both versions, feel free to |
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look at the debootstrap instance's |
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<filename>common.sh</filename> auxiliary script. |
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</para> |
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|
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<para> |
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Also, instances can have now a variable number of disks, not |
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only two, and a variable number of NICs (instead of fixed |
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one), so the scripts should deal with this. The biggest |
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change is in the import/export, which are called once per |
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disk, instead of once per instance. |
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</para> |
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|
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</refsect3> |
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|
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<refsect3> |
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<title>Version 4 to 5</title> |
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<para> |
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The <filename>rename</filename> script has been added. If |
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you don't want to do any changes on the instances after a |
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rename, you can migrate the OS definition to version 5 by |
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creating the <filename>rename</filename> script simply as: |
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<screen> |
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#!/bin/sh |
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|
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exit 0 |
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</screen> |
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</para> |
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|
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<para>Note that the script must be executable.</para> |
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</refsect3> |
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</refsect2> |
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|
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<!-- |
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<refsect2> |
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|
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<title>Export/import format</title> |
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|
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<para> |
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It is up to the export and import scripts to define the format |
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they use. It is only required for these two to work |
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together. It is not recommended that |
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</para> |
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|
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</refsect2> |
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--> |
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|
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</refsect1> |
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|
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&footer; |
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</refentry> |
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