<!--
doc/src/sgml/ref/initdb.sgml
PostgreSQL documentation
-->

<refentry id="app-initdb">
 <indexterm zone="app-initdb">
  <primary>initdb</primary>
 </indexterm>

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

 <refnamediv>
  <refname>initdb</refname>
  <refpurpose>create a new <productname>PostgreSQL</productname> database cluster</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
  <cmdsynopsis>
   <command>initdb</command>
   <arg rep="repeat"><replaceable>option</replaceable></arg>
   <group choice="plain">
    <group choice="opt">
     <arg choice="plain"><option>--pgdata</option></arg>
     <arg choice="plain"><option>-D</option></arg>
    </group>
    <replaceable> directory</replaceable>
   </group>
  </cmdsynopsis>
 </refsynopsisdiv>

 <refsect1 id="r1-app-initdb-1">
  <title>Description</title>
  <para>
   <command>initdb</command> creates a new
   <productname>PostgreSQL</productname> database cluster.  A database
   cluster is a collection of databases that are managed by a single
   server instance.
  </para>

  <para>
   Creating a database cluster consists of creating the directories in
   which the database data will live, generating the shared catalog
   tables (tables that belong to the whole cluster rather than to any
   particular database), and creating the <literal>template1</literal>
   and <literal>postgres</literal> databases. When you later create a
   new database, everything in the <literal>template1</literal> database is
   copied.  (Therefore, anything installed in <literal>template1</literal>
   is automatically copied into each database created later.)
   The <literal>postgres</literal> database is a default database meant
   for use by users, utilities and third party applications.
  </para>

  <para>
   Although <command>initdb</command> will attempt to create the
   specified data directory, it might not have permission if the parent
   directory of the desired data directory is root-owned. To initialize
   in such a setup, create an empty data directory as root, then use
   <command>chown</command> to assign ownership of that directory to the
   database user account, then <command>su</command> to become the
   database user to run <command>initdb</command>.
  </para>

  <para>
   <command>initdb</command> must be run as the user that will own the
   server process, because the server needs to have access to the
   files and directories that <command>initdb</command> creates.
   Since the server cannot be run as root, you must not run
   <command>initdb</command> as root either.  (It will in fact refuse
   to do so.)
  </para>

  <para>
    For security reasons the new cluster created by <command>initdb</command>
    will only be accessible by the cluster owner by default.  The
    <option>--allow-group-access</option> option allows any user in the same
    group as the cluster owner to read files in the cluster.  This is useful
    for performing backups as a non-privileged user.
  </para>

  <para>
   <command>initdb</command> initializes the database cluster's default
   locale and character set encoding. The character set encoding,
   collation order (<literal>LC_COLLATE</literal>) and character set classes
   (<literal>LC_CTYPE</literal>, e.g., upper, lower, digit) can be set separately
   for a database when it is created. <command>initdb</command> determines
   those settings for the <literal>template1</literal> database, which will
   serve as the default for all other databases.
  </para>

  <para>
   To alter the default collation order or character set classes, use the
   <option>--lc-collate</option> and <option>--lc-ctype</option> options.
   Collation orders other than <literal>C</literal> or <literal>POSIX</literal> also have
   a performance penalty.  For these reasons it is important to choose the
   right locale when running <command>initdb</command>.
  </para>

  <para>
   The remaining locale categories can be changed later when the server
   is started.  You can also use <option>--locale</option> to set the
   default for all locale categories, including collation order and
   character set classes. All server locale values (<literal>lc_*</literal>) can
   be displayed via <command>SHOW ALL</command>.
   More details can be found in <xref linkend="locale"/>.
  </para>

  <para>
   To alter the default encoding, use the <option>--encoding</option>.
   More details can be found in <xref linkend="multibyte"/>.
  </para>

 </refsect1>

 <refsect1>
  <title>Options</title>

   <para>
    <variablelist>
     <varlistentry>
      <term><option>-A <replaceable class="parameter">authmethod</replaceable></option></term>
      <term><option>--auth=<replaceable class="parameter">authmethod</replaceable></option></term>
      <listitem>
       <para>
        This option specifies the default authentication method for local
        users used in <filename>pg_hba.conf</filename> (<literal>host</literal>
        and <literal>local</literal> lines).  <command>initdb</command> will
        prepopulate <filename>pg_hba.conf</filename> entries using the
        specified authentication method for non-replication as well as
        replication connections.
       </para>

       <para>
        Do not use <literal>trust</literal> unless you trust all local users on your
        system.  <literal>trust</literal> is the default for ease of installation.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--auth-host=<replaceable class="parameter">authmethod</replaceable></option></term>
      <listitem>
       <para>
        This option specifies the authentication method for local users via
        TCP/IP connections used in <filename>pg_hba.conf</filename>
        (<literal>host</literal> lines).
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--auth-local=<replaceable class="parameter">authmethod</replaceable></option></term>
      <listitem>
       <para>
        This option specifies the authentication method for local users via
        Unix-domain socket connections used in <filename>pg_hba.conf</filename>
        (<literal>local</literal> lines).
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-D <replaceable class="parameter">directory</replaceable></option></term>
      <term><option>--pgdata=<replaceable class="parameter">directory</replaceable></option></term>
      <listitem>
       <para>
        This option specifies the directory where the database cluster
        should be stored. This is the only information required by
        <command>initdb</command>, but you can avoid writing it by
        setting the <envar>PGDATA</envar> environment variable, which
        can be convenient since the database server
        (<command>postgres</command>) can find the database
        directory later by the same variable.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-E <replaceable class="parameter">encoding</replaceable></option></term>
      <term><option>--encoding=<replaceable class="parameter">encoding</replaceable></option></term>
      <listitem>
       <para>
        Selects the encoding of the template database. This will also
        be the default encoding of any database you create later,
        unless you override it there.  The default is derived from the locale, or
        <literal>SQL_ASCII</literal> if that does not work. The character sets supported by
        the <productname>PostgreSQL</productname> server are described
        in <xref linkend="multibyte-charset-supported"/>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="app-initdb-allow-group-access" xreflabel="group access">
      <term><option>-g</option></term>
      <term><option>--allow-group-access</option></term>
      <listitem>
       <para>
        Allows users in the same group as the cluster owner to read all cluster
        files created by <command>initdb</command>.  This option is ignored
        on <productname>Windows</productname> as it does not support
        <acronym>POSIX</acronym>-style group permissions.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="app-initdb-data-checksums" xreflabel="data checksums">
      <term><option>-k</option></term>
      <term><option>--data-checksums</option></term>
      <listitem>
       <para>
        Use checksums on data pages to help detect corruption by the
        I/O system that would otherwise be silent. Enabling checksums
        may incur a noticeable performance penalty. If set, checksums
        are calculated for all objects, in all databases. All checksum
        failures will be reported in the
        <link linkend="monitoring-pg-stat-database-view">
        <structname>pg_stat_database</structname></link> view.
        See <xref linkend="checksums" /> for details.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--locale=<replaceable>locale</replaceable></option></term>
      <listitem>
       <para>
        Sets the default locale for the database cluster.  If this
        option is not specified, the locale is inherited from the
        environment that <command>initdb</command> runs in. Locale
        support is described in <xref linkend="locale"/>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--lc-collate=<replaceable>locale</replaceable></option></term>
      <term><option>--lc-ctype=<replaceable>locale</replaceable></option></term>
      <term><option>--lc-messages=<replaceable>locale</replaceable></option></term>
      <term><option>--lc-monetary=<replaceable>locale</replaceable></option></term>
      <term><option>--lc-numeric=<replaceable>locale</replaceable></option></term>
      <term><option>--lc-time=<replaceable>locale</replaceable></option></term>

      <listitem>
       <para>
        Like <option>--locale</option>, but only sets the locale in
        the specified category.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--no-locale</option></term>
      <listitem>
       <para>
        Equivalent to <option>--locale=C</option>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-N</option></term>
      <term><option>--no-sync</option></term>
      <listitem>
       <para>
        By default, <command>initdb</command> will wait for all files to be
        written safely to disk.  This option causes <command>initdb</command>
        to return without waiting, which is faster, but means that a
        subsequent operating system crash can leave the data directory
        corrupt.  Generally, this option is useful for testing, but should not
        be used when creating a production installation.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--no-instructions</option></term>
      <listitem>
       <para>
        By default, <command>initdb</command> will write instructions for how
        to start the cluster at the end of its output. This option causes
        those instructions to be left out. This is primarily intended for use
        by tools that wrap <command>initdb</command> in platform-specific
        behavior, where those instructions are likely to be incorrect.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--pwfile=<replaceable>filename</replaceable></option></term>
      <listitem>
       <para>
        Makes <command>initdb</command> read the database superuser's password
        from a file.  The first line of the file is taken as the password.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-S</option></term>
      <term><option>--sync-only</option></term>
      <listitem>
       <para>
        Safely write all database files to disk and exit.  This does not
        perform any of the normal <application>initdb</application> operations.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-T <replaceable>config</replaceable></option></term>
      <term><option>--text-search-config=<replaceable>config</replaceable></option></term>
      <listitem>
       <para>
        Sets the default text search configuration.
        See <xref linkend="guc-default-text-search-config"/> for further information.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-U <replaceable class="parameter">username</replaceable></option></term>
      <term><option>--username=<replaceable class="parameter">username</replaceable></option></term>
      <listitem>
       <para>
        Selects the user name of the database superuser. This defaults
        to the name of the effective user running
        <command>initdb</command>. It is really not important what the
        superuser's name is, but one might choose to keep the
        customary name <systemitem>postgres</systemitem>, even if the operating
        system user's name is different.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-W</option></term>
      <term><option>--pwprompt</option></term>
      <listitem>
       <para>
        Makes <command>initdb</command> prompt for a password
        to give the database superuser. If you don't plan on using password
        authentication, this is not important.  Otherwise you won't be
        able to use password authentication until you have a password
        set up.
       </para>
      </listitem>
     </varlistentry>

      <varlistentry>
      <term><option>-X <replaceable class="parameter">directory</replaceable></option></term>
      <term><option>--waldir=<replaceable class="parameter">directory</replaceable></option></term>
      <listitem>
       <para>
        This option specifies the directory where the write-ahead log
        should be stored.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--wal-segsize=<replaceable>size</replaceable></option></term>
      <listitem>
       <para>
        Set the <firstterm>WAL segment size</firstterm>, in megabytes.  This
        is the size of each individual file in the WAL log.  The default size
        is 16 megabytes.  The value must be a power of 2 between 1 and 1024
        (megabytes).  This option can only be set during initialization, and
        cannot be changed later.
       </para>

       <para>
        It may be useful to adjust this size to control the granularity of
        WAL log shipping or archiving.  Also, in databases with a high volume
        of WAL, the sheer number of WAL files per directory can become a
        performance and management problem.  Increasing the WAL file size
        will reduce the number of WAL files.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
   </para>

   <para>
    Other, less commonly used, options are also available:

    <variablelist>
     <varlistentry>
      <term><option>-d</option></term>
      <term><option>--debug</option></term>
      <listitem>
       <para>
        Print debugging output from the bootstrap backend and a few other
        messages of lesser interest for the general public.
        The bootstrap backend is the program <command>initdb</command>
        uses to create the catalog tables.  This option generates a tremendous
        amount of extremely boring output.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>--discard-caches</option></term>
      <listitem>
       <para>
        Run the bootstrap backend with the
        <literal>debug_discard_caches=1</literal> option.
        This takes a very long time and is only of use for deep debugging.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-L <replaceable class="parameter">directory</replaceable></option></term>
      <listitem>
       <para>
        Specifies where <command>initdb</command> should find
        its input files to initialize the database cluster.  This is
        normally not necessary.  You will be told if you need to
        specify their location explicitly.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term><option>-n</option></term>
      <term><option>--no-clean</option></term>
      <listitem>
       <para>
        By default, when <command>initdb</command>
        determines that an error prevented it from completely creating the database
        cluster, it removes any files it might have created before discovering
        that it cannot finish the job. This option inhibits tidying-up and is
        thus useful for debugging.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
   </para>

   <para>
    Other options:

    <variablelist>
     <varlistentry>
       <term><option>-V</option></term>
       <term><option>--version</option></term>
       <listitem>
       <para>
       Print the <application>initdb</application> version and exit.
       </para>
       </listitem>
     </varlistentry>

     <varlistentry>
       <term><option>-?</option></term>
       <term><option>--help</option></term>
       <listitem>
       <para>
       Show help about <application>initdb</application> command line
       arguments, and exit.
       </para>
       </listitem>
     </varlistentry>

    </variablelist>
   </para>

 </refsect1>

 <refsect1>
  <title>Environment</title>

  <variablelist>
   <varlistentry>
    <term><envar>PGDATA</envar></term>

    <listitem>
     <para>
      Specifies the directory where the database cluster is to be
      stored; can be overridden using the <option>-D</option> option.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><envar>PG_COLOR</envar></term>
    <listitem>
     <para>
      Specifies whether to use color in diagnostic messages. Possible values
      are <literal>always</literal>, <literal>auto</literal> and
      <literal>never</literal>.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><envar>TZ</envar></term>

    <listitem>
     <para>
      Specifies the default time zone of the created database cluster.  The
      value should be a full time zone name
      (see <xref linkend="datatype-timezones"/>).
     </para>
    </listitem>
   </varlistentry>
  </variablelist>

 </refsect1>

 <refsect1>
  <title>Notes</title>

  <para>
   <command>initdb</command> can also be invoked via
   <command>pg_ctl initdb</command>.
  </para>
 </refsect1>

 <refsect1>
  <title>See Also</title>

  <simplelist type="inline">
   <member><xref linkend="app-pg-ctl"/></member>
   <member><xref linkend="app-postgres"/></member>
  </simplelist>
 </refsect1>

</refentry>
