<!--
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>
   <arg choice="plain">
    <group choice="opt">
     <arg choice="plain"><option>--pgdata</option></arg>
     <arg choice="plain"><option>-D</option></arg>
    </group>
    <replaceable>datadir</replaceable>
   </arg>
  </cmdsynopsis>
 </refsynopsisdiv>

 <refsect1 id="r1-app-initdb-1">
  <title>Description</title>
  <para>
   <command>initdb</command> creates a new
   <productname>PostgreSQL</productname> <glossterm linkend="glossary-db-cluster">database cluster</glossterm>.
  </para>

  <para>
   Creating a database cluster consists of creating the
   <glossterm linkend="glossary-data-directory">directories</glossterm> in
   which the cluster 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.
  </para>

  <para>
   By default, <command>initdb</command> uses the locale provider
   <literal>libc</literal> (see <xref linkend="locale-providers"/>). The
   <literal>libc</literal> locale provider takes the locale settings from the
   environment, and determines the encoding from the locale settings.
  </para>

  <para>
   To choose a different locale for the cluster, use the option
   <option>--locale</option>.  There are also individual options
   <option>--lc-*</option> and <option>--icu-locale</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, <command>initdb</command> can use the ICU library to provide
   locale services by specifying <literal>--locale-provider=icu</literal>. The
   server must be built with ICU support. 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 id="app-initdb-option-auth">
      <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 id="app-initdb-option-auth-host">
      <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 id="app-initdb-option-auth-local">
      <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 id="app-initdb-option-pgdata">
      <term><option>-D <replaceable class="parameter">datadir</replaceable></option></term>
      <term><option>--pgdata=<replaceable class="parameter">datadir</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 data
        directory later by the same variable.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="app-initdb-option-encoding">
      <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 character sets supported by the
        <productname>PostgreSQL</productname> server are described in <xref
        linkend="multibyte-charset-supported"/>.
       </para>
       <para>
        By default, the template database encoding is derived from the
        locale. If <xref linkend="app-initdb-option-no-locale"/> is specified
        (or equivalently, if the locale is <literal>C</literal> or
        <literal>POSIX</literal>), then the default is <literal>UTF8</literal>
        for the ICU provider and <literal>SQL_ASCII</literal> for the
        <literal>libc</literal> provider.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="app-initdb-allow-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-icu-locale">
      <term><option>--icu-locale=<replaceable>locale</replaceable></option></term>
      <listitem>
       <para>
        Specifies the ICU locale when the ICU provider is used. Locale support
        is described in <xref linkend="locale"/>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="app-initdb-icu-rules">
      <term><option>--icu-rules=<replaceable>rules</replaceable></option></term>
      <listitem>
       <para>
        Specifies additional collation rules to customize the behavior of the
        default collation.  This is supported for ICU only.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="app-initdb-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.  This is enabled by default;
        use <xref linkend="app-initdb-no-data-checksums"/> to disable
        checksums.
       </para>

       <para>
        Enabling checksums
        might incur a small 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 id="app-initdb-option-locale">
      <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>
       <para>
        If <option>--locale-provider</option> is <literal>builtin</literal>,
        <option>--locale</option> or <option>--builtin-locale</option> must be
        specified and set to <literal>C</literal>, <literal>C.UTF-8</literal>
        or <literal>PG_UNICODE_FAST</literal>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="app-initdb-option-lc-collate">
      <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 id="app-initdb-option-no-locale">
      <term><option>--no-locale</option></term>
      <listitem>
       <para>
        Equivalent to <option>--locale=C</option>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="app-initdb-builtin-locale">
      <term><option>--builtin-locale=<replaceable>locale</replaceable></option></term>
      <listitem>
       <para>
        Specifies the locale name when the builtin provider is used. Locale support
        is described in <xref linkend="locale"/>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="app-initdb-option-locale-provider">
      <term><option>--locale-provider={<literal>builtin</literal>|<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> (see <xref
        linkend="locale-providers"/>).
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="app-initdb-no-data-checksums">
      <term><option>--no-data-checksums</option></term>
      <listitem>
       <para>
        Do not enable data checksums.
       </para>
      </listitem>
     </varlistentry>

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

     <varlistentry id="app-initdb-option-text-search-config">
      <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 id="app-initdb-option-username">
      <term><option>-U <replaceable class="parameter">username</replaceable></option></term>
      <term><option>--username=<replaceable class="parameter">username</replaceable></option></term>
      <listitem>
       <para>
        Sets the user name of the
        <glossterm linkend="glossary-bootstrap-superuser">bootstrap superuser</glossterm>.
        This defaults to the name of the operating-system user running
        <command>initdb</command>.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="app-initdb-option-pwprompt">
      <term><option>-W</option></term>
      <term><option>--pwprompt</option></term>
      <listitem>
       <para>
        Makes <command>initdb</command> prompt for a password
        to give the bootstrap 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 id="app-initdb-option-waldir">
      <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 id="app-initdb-option-wal-segsize">
      <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 id="app-initdb-option-set">
      <term><option>-c <replaceable>name</replaceable>=<replaceable>value</replaceable></option></term>
      <term><option>--set <replaceable>name</replaceable>=<replaceable>value</replaceable></option></term>
      <listitem>
       <para>
        Forcibly set the server parameter <replaceable>name</replaceable>
        to <replaceable>value</replaceable> during <command>initdb</command>,
        and also install that setting in the
        generated <filename>postgresql.conf</filename> file,
        so that it will apply during future server runs.
        This option can be given more than once to set several parameters.
        It is primarily useful when the environment is such that the server
        will not start at all using the default parameters.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="app-initdb-option-debug">
      <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 id="app-initdb-option-discard-caches">
      <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 id="app-initdb-option-l">
      <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 id="app-initdb-option-no-clean">
      <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>

     <varlistentry id="app-initdb-option-no-sync">
      <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 id="app-initdb-option-no-sync-data-files">
      <term><option>--no-sync-data-files</option></term>
      <listitem>
       <para>
        By default, <command>initdb</command> safely writes all database files
        to disk.  This option instructs <command>initdb</command> to skip
        synchronizing all files in the individual database directories, the
        database directories themselves, and the tablespace directories, i.e.,
        everything in the <filename>base</filename> subdirectory and any other
        tablespace directories.  Other files, such as those in
        <literal>pg_wal</literal> and <literal>pg_xact</literal>, will still be
        synchronized unless the <option>--no-sync</option> option is also
        specified.
       </para>
       <para>
        Note that if <option>--no-sync-data-files</option> is used in
        conjunction with <option>--sync-method=syncfs</option>, some or all of
        the aforementioned files and directories will be synchronized because
        <literal>syncfs</literal> processes entire file systems.
       </para>
       <para>
        This option is primarily intended for internal use by tools that
        separately ensure the skipped files are synchronized to disk.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="app-initdb-option-no-instructions">
      <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 id="app-initdb-option-show">
      <term><option>-s</option></term>
      <term><option>--show</option></term>
      <listitem>
       <para>
        Show internal settings and exit, without doing anything else.  This
        can be used to debug the <application>initdb</application>
        installation.
       </para>
      </listitem>
     </varlistentry>

     <varlistentry id="app-initdb-option-sync-method">
      <term><option>--sync-method=<replaceable>method</replaceable></option></term>
      <listitem>
       <para>
        When set to <literal>fsync</literal>, which is the default,
        <command>initdb</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 id="app-initdb-option-sync-only">
      <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>
    </variablelist>
   </para>

   <para>
    Other options:

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

     <varlistentry id="app-initdb-option-help">
       <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 id="app-initdb-environment-pgdata">
    <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 id="app-initdb-environment-pg-color">
    <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 id="app-initdb-environment-tz">
    <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>
   <member><xref linkend="auth-pg-hba-conf"/></member>
  </simplelist>
 </refsect1>

</refentry>
