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b5f640d04d
- add undocumented events (per report from Daymel Bonne) - split up list into sections for better overview - where feasible, add cross-links
368 lines
13 KiB
Plaintext
368 lines
13 KiB
Plaintext
<refentry id="repmgr-standby-clone">
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<indexterm>
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<primary>repmgr standby clone</primary>
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<seealso>cloning</seealso>
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</indexterm>
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<refmeta>
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<refentrytitle>repmgr standby clone</refentrytitle>
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</refmeta>
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<refnamediv>
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<refname>repmgr standby clone</refname>
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<refpurpose>clone a PostgreSQL standby node from another PostgreSQL node</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<para>
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<command>repmgr standby clone</command> clones a PostgreSQL node from another
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PostgreSQL node, typically the primary, but optionally from any other node in
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the cluster or from Barman. It creates the <filename>recovery.conf</filename> file required
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to attach the cloned node to the primary node (or another standby, if cascading replication
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is in use).
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</para>
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<note>
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<simpara>
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<command>repmgr standby clone</command> does not start the standby, and after cloning
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a standby, the command <command>repmgr standby register</command> must be executed to
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notify &repmgr; of its existence.
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</simpara>
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</note>
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</refsect1>
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<refsect1 id="repmgr-standby-clone-config-file-copying" xreflabel="Copying configuration files">
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<title>Handling configuration files</title>
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<para>
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Note that by default, all configuration files in the source node's data
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directory will be copied to the cloned node. Typically these will be
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<filename>postgresql.conf</filename>, <filename>postgresql.auto.conf</filename>,
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<filename>pg_hba.conf</filename> and <filename>pg_ident.conf</filename>.
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These may require modification before the standby is started.
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</para>
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<para>
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In some cases (e.g. on Debian or Ubuntu Linux installations), PostgreSQL's
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configuration files are located outside of the data directory and will
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not be copied by default. &repmgr; can copy these files, either to the same
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location on the standby server (provided appropriate directory and file permissions
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are available), or into the standby's data directory. This requires passwordless
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SSH access to the primary server. Add the option <option>--copy-external-config-files</option>
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to the <command>repmgr standby clone</command> command; by default files will be copied to
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the same path as on the upstream server. Note that the user executing <command>repmgr</command>
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must have write access to those directories.
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</para>
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<para>
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To have the configuration files placed in the standby's data directory, specify
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<literal>--copy-external-config-files=pgdata</literal>, but note that
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any include directives in the copied files may need to be updated.
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</para>
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<note>
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<para>
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When executing <command>repmgr standby clone</command> with the
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<option>--copy-external-config-files</option> aand <option>--dry-run</option>
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options, &repmgr; will check the SSH connection to the source node, but
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will not verify whether the files can actually be copied.
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</para>
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<para>
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During the actual clone operation, a check will be made before the database itself
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is cloned to determine whether the files can actually be copied; if any problems are
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encountered, the clone operation will be aborted, enabling the user to fix
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any issues before retrying the clone operation.
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</para>
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</note>
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<tip>
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<simpara>
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For reliable configuration file management we recommend using a
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configuration management tool such as Ansible, Chef, Puppet or Salt.
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</simpara>
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</tip>
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</refsect1>
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<refsect1 id="repmgr-standby-clone-recovery-conf">
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<indexterm>
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<primary>recovery.conf</primary>
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<secondary>customising with "repmgr standby clone"</secondary>
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</indexterm>
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<title>Customising recovery.conf</title>
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<para>
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By default, &repmgr; will create a minimal <filename>recovery.conf</filename>
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containing following parameters:
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</para>
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<itemizedlist spacing="compact" mark="bullet">
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<listitem>
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<simpara><varname>standby_mode</varname> (always <literal>'on'</literal>)</simpara>
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</listitem>
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<listitem>
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<simpara><varname>recovery_target_timeline</varname> (always <literal>'latest'</literal>)</simpara>
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</listitem>
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<listitem>
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<simpara><varname>primary_conninfo</varname></simpara>
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</listitem>
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<listitem>
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<simpara><varname>primary_slot_name</varname> (if replication slots in use)</simpara>
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</listitem>
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</itemizedlist>
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<para>
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The following additional parameters can be specified in <filename>repmgr.conf</filename>
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for inclusion in <filename>recovery.conf</filename>:
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</para>
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<itemizedlist spacing="compact" mark="bullet">
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<listitem>
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<simpara><varname>restore_command</varname></simpara>
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</listitem>
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<listitem>
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<simpara><varname>archive_cleanup_command</varname></simpara>
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</listitem>
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<listitem>
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<simpara><varname>recovery_min_apply_delay</varname></simpara>
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</listitem>
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</itemizedlist>
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<note>
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<para>
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We recommend using <ulink url="https://www.pgbarman.org/">Barman</ulink> to manage
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WAL file archiving. For more details on combining &repmgr; and <application>Barman</application>,
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in particular using <varname>restore_command</varname> to configure Barman as a backup source of
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WAL files, see <xref linkend="cloning-from-barman">.
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</para>
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</note>
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</refsect1>
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<refsect1 id="repmgr-standby-clone-wal-management">
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<title>Managing WAL during the cloning process</title>
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<para>
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When initially cloning a standby, you will need to ensure
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that all required WAL files remain available while the cloning is taking
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place. To ensure this happens when using the default <command>pg_basebackup</command> method,
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&repmgr; will set <command>pg_basebackup</command>'s <literal>--xlog-method</literal>
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parameter to <literal>stream</literal>,
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which will ensure all WAL files generated during the cloning process are
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streamed in parallel with the main backup. Note that this requires two
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replication connections to be available (&repmgr; will verify sufficient
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connections are available before attempting to clone, and this can be checked
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before performing the clone using the <literal>--dry-run</literal> option).
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</para>
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<para>
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To override this behaviour, in <filename>repmgr.conf</filename> set
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<command>pg_basebackup</command>'s <literal>--xlog-method</literal>
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parameter to <literal>fetch</literal>:
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<programlisting>
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pg_basebackup_options='--xlog-method=fetch'</programlisting>
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and ensure that <literal>wal_keep_segments</literal> is set to an appropriately high value.
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See the <ulink url="https://www.postgresql.org/docs/current/static/app-pgbasebackup.html">
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pg_basebackup</ulink> documentation for details.
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</para>
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<note>
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<simpara>
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From PostgreSQL 10, <command>pg_basebackup</command>'s
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<literal>--xlog-method</literal> parameter has been renamed to
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<literal>--wal-method</literal>.
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</simpara>
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</note>
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</refsect1>
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<refsect1 id="repmgr-standby-create-recovery-conf">
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<indexterm>
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<primary>recovery.conf</primary>
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<secondary>generating for a standby cloned by another method</secondary>
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</indexterm>
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<title>Using a standby cloned by another method</title>
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<para>
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&repmgr; supports standbys cloned by another method (e.g. using <application>barman</application>'s
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<command><ulink url="http://docs.pgbarman.org/release/2.4/#recover">barman recover</ulink></command> command).
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</para>
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<para>
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To integrate the standby as a &repmgr; node, ensure the <filename>repmgr.conf</filename>
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file is created for the node, and that it has been registered using
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<command><link linkend="repmgr-standby-register">repmgr standby register</link></command>.
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Then execute the command <command>repmgr standby clone --recovery-conf-only</command>.
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This will create the <filename>recovery.conf</filename> file needed to attach
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the node to its upstream, and will also create a replication slot on the
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upstream node if required.
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</para>
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<para>
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Note that the upstream node must be running. An existing
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<filename>recovery.conf</filename> will not be overwritten unless the
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<option>-F/--force</option> option is provided.
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</para>
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<para>
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Execute <command>repmgr standby clone --recovery-conf-only --dry-run</command>
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to check the prerequisites for creating the <filename>recovery.conf</filename> file,
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and display the contents of the file without actually creating it.
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</para>
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<note>
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<para>
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<option>--recovery-conf-only</option> was introduced in &repmgr; <link linkend="release-4.0.4">4.0.4</link>.
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</para>
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</note>
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</refsect1>
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<refsect1>
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<title>Options</title>
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<variablelist>
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<varlistentry>
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<term><option>-d, --dbname=CONNINFO</option></term>
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<listitem>
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<para>
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Connection string of the upstream node to use for cloning.
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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><option>--dry-run</option></term>
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<listitem>
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<para>
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Check prerequisites but don't actually clone the standby.
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</para>
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<para>
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If <option>--recovery-conf-only</option> specified, the contents of
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the generated <filename>recovery.conf</filename> file will be displayed
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but the file itself not written.
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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><option>-c, --fast-checkpoint</option></term>
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<listitem>
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<para>
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Force fast checkpoint (not effective when cloning from Barman).
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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><option>--copy-external-config-files[={samepath|pgdata}]</option></term>
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<listitem>
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<para>
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Copy configuration files located outside the data directory on the source
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node to the same path on the standby (default) or to the
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PostgreSQL data directory.
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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><option>--no-upstream-connection</option></term>
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<listitem>
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<para>
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When using Barman, do not connect to upstream node.
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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><option>-R, --remote-user=USERNAME</option></term>
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<listitem>
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<para>
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Remote system username for SSH operations (default: current local system username).
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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><option> --recovery-conf-only</option></term>
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<listitem>
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<para>
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Create <filename>recovery.conf</filename> file for a previously cloned instance. &repmgr 4.0.4 and later.
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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><option>--replication-user</option></term>
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<listitem>
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<para>
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User to make replication connections with (optional, not usually required).
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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><option>--superuser</option></term>
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<listitem>
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<para>
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If the &repmgr; user is not a superuser, the name of a valid superuser must
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be provided with this option.
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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><option>--upstream-conninfo</option></term>
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<listitem>
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<para>
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<literal>primary_conninfo</literal> value to write in recovery.conf
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when the intended upstream server does not yet exist.
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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><option>--upstream-node-id</option></term>
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<listitem>
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<para>
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ID of the upstream node to replicate from (optional, defaults to primary node)
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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><option>--without-barman </option></term>
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<listitem>
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<para>
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Do not use Barman even if configured.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 id="repmgr-standby-clone-events">
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<title>Event notifications</title>
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<para>
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A <literal>standby_clone</literal> <link linkend="event-notifications">event notification</link> will be generated.
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</para>
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</refsect1>
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<refsect1>
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<title>See also</title>
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<para>
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See <xref linkend="cloning-standbys"> for details about various aspects of cloning.
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</para>
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</refsect1>
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</refentry>
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