class="parameter">method</replaceable></option></term>
      <listitem>
       <para>
        When set to <literal>fsync</literal>, which is the default,
        <command>pg_rewind</command> will recursively open and synchronize all
        files in the data directory.  The search for files will follow symbolic
        links for the WAL directory and each configured tablespace.
       </para>
       <para>
        On Linux, <literal>syncfs</literal> may be used instead to ask the
        operating system to synchronize the whole file systems that contain the
        data directory, the WAL files, and each tablespace.  See
        <xref linkend="guc-recovery-init-sync-method"/> for information about
        the caveats to be aware of when using <literal>syncfs</literal>.
       </para>
       <para>
        This option has no effect when <option>--no-sync</option> is used.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-V</option></term>
      <term><option>--version</option></term>
      <listitem><para>Display version information, then exit.</para></listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-?</option></term>
      <term><option>--help</option></term>
      <listitem><para>Show help, then exit.</para></listitem>
     </varlistentry>

    </variablelist>
   </para>
 </refsect1>

 <refsect1>
  <title>Environment</title>

  <para>
   When <option>--source-server</option> option is used,
   <application>pg_rewind</application> also uses the environment variables
   supported by <application>libpq</application> (see <xref linkend="libpq-envars"/>).
  </para>

  <para>
   The environment variable <envar>PG_COLOR</envar> specifies whether to use
   color in diagnostic messages. Possible values are
   <literal>always</literal>, <literal>auto</literal> and
   <literal>never</literal>.
  </para>
 </refsect1>

 <refsect1>
  <title>Notes</title>

  <para>
   When executing <application>pg_rewind</application> using an online
   cluster as source, a role having sufficient permissions to execute the
   functions used by <application>pg_rewind</application> on the source
   cluster can be used instead of a superuser.  Here is how to create such
   a role, named <literal>rewind_user</literal> here:
<programlisting>
CREATE USER rewind_user LOGIN;
GRANT EXECUTE ON function pg_catalog.pg_ls_dir(text, boolean, boolean) TO rewind_user;
GRANT EXECUTE ON function pg_catalog.pg_stat_file(text, boolean) TO rewind_user;
GRANT EXECUTE ON function pg_catalog.pg_read_binary_file(text) TO rewind_user;
GRANT EXECUTE ON function pg_catalog.pg_read_binary_file(text, bigint, bigint, boolean) TO rewind_user;
</programlisting>
  </para>

  <refsect2>
   <title>How It Works</title>

   <para>
    The basic idea is to copy all file system-level changes from the source
    cluster to the target cluster:
   </para>

   <procedure>