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doc/src/sgml/ref/pg_combinebackup.sgml
PostgreSQL documentation
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<refentry id="app-pgcombinebackup">
 <indexterm zone="app-pgcombinebackup">
  <primary>pg_combinebackup</primary>
 </indexterm>

 <refmeta>
  <refentrytitle><application>pg_combinebackup</application></refentrytitle>
  <manvolnum>1</manvolnum>
  <refmiscinfo>Application</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>pg_combinebackup</refname>
  <refpurpose>reconstruct a full backup from an incremental backup and dependent backups</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
  <cmdsynopsis>
   <command>pg_combinebackup</command>
   <arg rep="repeat"><replaceable>option</replaceable></arg>
   <arg rep="repeat"><replaceable>backup_directory</replaceable></arg>
  </cmdsynopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>
  <para>
   <application>pg_combinebackup</application> is used to reconstruct a
   synthetic full backup from an
   <link linkend="backup-incremental-backup">incremental backup</link> and the
   earlier backups upon which it depends.
  </para>

  <para>
   Specify all of the required backups on the command line from oldest to newest.
   That is, the first backup directory should be the path to the full backup, and
   the last should be the path to the final incremental backup
   that you wish to restore. The reconstructed backup will be written to the
   output directory specified by the <option>-o</option> option.
  </para>

  <para>
   <application>pg_combinebackup</application> will attempt to verify
   that the backups you specify form a legal backup chain from which a correct
   full backup can be reconstructed. However, it is not designed to help you
   keep track of which backups depend on which other backups. If you remove
   one or more of the previous backups upon which your incremental
   backup relies, you will not be able to restore it. Moreover,
   <application>pg_combinebackup</application> only attempts to verify that the
   backups have the correct relationship to each other, not that each
   individual backup is intact; for that, use
   <xref linkend="app-pgverifybackup" />.
  </para>

  <para>
   Since the output of <application>pg_combinebackup</application> is a
   synthetic full backup, it can be used as an input to a future invocation of
   <application>pg_combinebackup</application>. The synthetic full backup would
   be specified on the command line in lieu of the chain of backups from which
   it was reconstructed.
  </para>
 </refsect1>

 <refsect1>
  <title>Options</title>

   <para>
    <variablelist>
     <varlistentry>
      <term><option>-d</option></term>
      <term><option>--debug</option></term>
      <listitem>
       <para>
        Print lots of debug logging output on <filename>stderr</filename>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-k</option></term>
      <term><option>--link</option></term>
      <listitem>
       <para>
        Use hard links instead of copying files to the synthetic backup.
        Reconstruction of the synthetic backup might be faster (no file copying)
        and use less disk space, but care must be taken when using the output
        directory, because any modifications to that directory (for example,
        starting the server) can also affect the input directories. Likewise,
        changes to the input directories (for example, starting the server on
        the full backup) could affect the output directory. Thus, this option
        is best used when the input directories are only copies that will be
        removed after <application>pg_combinebackup</application> has completed.
       </para>

       <para>
        Requires that the input backups and the output directory are in the
        same file system.
       </para>

       <para>
        If a backup manifest is not available or does not contain checksum of
        the right type, hard links will still be created, but the file will be