<!--
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>postgres</literal>,
   <literal>template1</literal>, and <literal>template0</literal> databases.
   The <literal>postgres</literal> database is a default database meant
   for use by users, utilities and third party applications.
   <literal>template1</literal> and <literal>template0</literal> are
   meant as source databases to be copied by later <command>CREATE
   DATABASE</command> commands.  <literal>template0</literal> should never
   be modified, but you can add objects to <literal>template1</literal>,
   which by default will be copied into databases created later.  See
   <xref linkend="manage-ag-templatedbs"/> for more details.
  </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. These can also be set separately for each
   database when it is created. <command>initdb</command> determines those
   settings for the template databases, which will serve as the default for
   all other databases.  By default, <command>initdb</command> uses the
   locale provider <literal>libc</literal>, takes the locale settings from
   the environment, and determines the encoding from the locale settings.
   This is almost always sufficient, unless there are special requirements.
  </para>

  <para>
   To choose a different locale for the cluster, use the option
   <option>--locale</option>.  There are also individual options
   <option>--lc-*</option> (see below) to set values for the individual locale
   categories.  Note that inconsistent settings for different locale
   categories can give nonsensical results, so this should be used with care.
  </para>

  <para>
   Alternatively, the ICU library can be used to provide locale services.
   (Again, this only sets the default for subsequently created databases.)  To
   select this option, specify <literal>--locale-provider=icu</literal>.
   To choose the specific ICU locale ID to apply, use the option
   <option>--icu-locale</option>.  Note that
   for implementation reasons and to support legacy code,
   <command>initdb</command> will still select and initialize libc locale
   settings when the ICU locale provider is used.
  </para>

  <para>
   When <command>initdb</command> runs, it will print out the locale settings
   it has chosen.  If you have complex requirements or specified multiple
   options, it is advisable to check that the result matches what was
   intended.
  </para>

  <para>
   More details about locale settings 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).  See <xref linkend="auth-pg-hba-conf"/>
        for an overview of valid values.
       </para>

       <para>
        <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 databases. This will also
        be the default encoding of any database you create later,
        unless you override it then.  The default is derived from the locale,
        if the libc locale provider is used, or <literal>UTF8</literal> if the
        ICU locale provider is used.  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>
      <term><option>--icu-locale=<replaceable>locale</replaceable></option></term>
      <listitem>
       <para>
        Specifies the ICU locale ID, if the ICU locale provider is used.
       </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>--locale-provider={<literal>libc</literal>|<literal>icu</literal>}</option></term>
      <listitem>
       <para>
        This option sets the locale provider for databases created in the
        new cluster.  It can be overridden in the <command>CREATE
        DATABASE</command> command when new databases are subsequently
        created.  The default is <literal>libc</literal>.
       </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.
        Generally, this option is useful for ensuring reliable recovery after
        changing <xref linkend="guc-fsync"/> from <literal>off</literal> to
        <literal>on</literal>.
       </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>

  <para>
   This utility, like most other <productname>PostgreSQL</productname> utilities,
   also uses the environment variables supported by <application>libpq</application>
   (see <xref linkend="libpq-envars"/>).
  </para>

 </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>
   <member><xref linkend="auth-pg-hba-conf"/></member>
  </simplelist>
 </refsect1>

</refentry>
