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  1. <?xml version="1.0" encoding="UTF-8" standalone="no"?>

  2. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>postgres</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="prev" href="pgwaldump.html" title="pg_waldump" /><link rel="next" href="app-postmaster.html" title="postmaster" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center"><span xmlns="http://www.w3.org/1999/xhtml" class="application">postgres</span></th></tr><tr><td width="10%" align="left"><a accesskey="p" href="pgwaldump.html" title="pg_waldump">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="reference-server.html" title="PostgreSQL Server Applications">Up</a></td><th width="60%" align="center">PostgreSQL Server Applications</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 12.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="app-postmaster.html" title="postmaster">Next</a></td></tr></table><hr></hr></div><div class="refentry" id="APP-POSTGRES"><div class="titlepage"></div><a id="id-1.9.5.14.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle"><span class="application">postgres</span></span></h2><p>postgres — <span class="productname">PostgreSQL</span> database server</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="cmdsynopsis"><p id="id-1.9.5.14.4.1"><code class="command">postgres</code> [<em class="replaceable"><code>option</code></em>...]</p></div></div><div class="refsect1" id="id-1.9.5.14.5"><h2>Description</h2><p>

  3.    <code class="command">postgres</code> is the

  4.    <span class="productname">PostgreSQL</span> database server.  In order

  5.    for a client application to access a database it connects (over a

  6.    network or locally) to a running <code class="command">postgres</code> instance.

  7.    The <code class="command">postgres</code> instance then starts a separate server

  8.    process to handle the connection.

  9.   </p><p>

  10.    One <code class="command">postgres</code> instance always manages the data of

  11.    exactly one database cluster.  A database cluster is a collection

  12.    of databases that is stored at a common file system location (the

  13.    <span class="quote">“<span class="quote">data area</span>”</span>).  More than one

  14.    <code class="command">postgres</code> instance can run on a system at one

  15.    time, so long as they use different data areas and different

  16.    communication ports (see below).  When

  17.    <code class="command">postgres</code> starts it needs to know the location

  18.    of the data area.  The location must be specified by the

  19.    <code class="option">-D</code> option or the <code class="envar">PGDATA</code> environment

  20.    variable; there is no default.  Typically, <code class="option">-D</code> or

  21.    <code class="envar">PGDATA</code> points directly to the data area directory

  22.    created by <a class="xref" href="app-initdb.html" title="initdb"><span class="refentrytitle">initdb</span></a>.  Other possible file layouts are

  23.    discussed in <a class="xref" href="runtime-config-file-locations.html" title="19.2. File Locations">Section 19.2</a>.

  24.   </p><p>

  25.    By default <code class="command">postgres</code> starts in the

  26.    foreground and prints log messages to the standard error stream.  In

  27.    practical applications <code class="command">postgres</code>

  28.    should be started as a background process, perhaps at boot time.

  29.   </p><p>

  30.    The <code class="command">postgres</code> command can also be called in

  31.    single-user mode.  The primary use for this mode is during

  32.    bootstrapping by <a class="xref" href="app-initdb.html" title="initdb"><span class="refentrytitle">initdb</span></a>.  Sometimes it is used

  33.    for debugging or disaster recovery;  note that running a single-user

  34.    server is not truly suitable for debugging the server, since no

  35.    realistic interprocess communication and locking will happen.

  36.    When invoked in single-user

  37.    mode from the shell, the user can enter queries and the results

  38.    will be printed to the screen, but in a form that is more useful

  39.    for developers than end users.  In the single-user mode,

  40.    the session user will be set to the user with ID 1, and implicit

  41.    superuser powers are granted to this user.

  42.    This user does not actually have to exist, so the single-user mode

  43.    can be used to manually recover from certain

  44.    kinds of accidental damage to the system catalogs.

  45.   </p></div><div class="refsect1" id="APP-POSTGRES-OPTIONS"><h2>Options</h2><p>

  46.     <code class="command">postgres</code> accepts the following command-line

  47.     arguments.  For a detailed discussion of the options consult <a class="xref" href="runtime-config.html" title="Chapter 19. Server Configuration">Chapter 19</a>.  You can save typing most of these

  48.     options by setting up a configuration file.  Some (safe) options

  49.     can also be set from the connecting client in an

  50.     application-dependent way to apply only for that session.  For

  51.     example, if the environment variable <code class="envar">PGOPTIONS</code> is

  52.     set, then <span class="application">libpq</span>-based clients will pass that

  53.     string to the server, which will interpret it as

  54.     <code class="command">postgres</code> command-line options.

  55.    </p><div class="refsect2" id="id-1.9.5.14.6.3"><h3>General Purpose</h3><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">-B <em class="replaceable"><code>nbuffers</code></em></code></span></dt><dd><p>

  56.         Sets the number of shared buffers for use by the server

  57.         processes.  The default value of this parameter is chosen

  58.         automatically by <span class="application">initdb</span>.

  59.         Specifying this option is equivalent to setting the

  60.         <a class="xref" href="runtime-config-resource.html#GUC-SHARED-BUFFERS">shared_buffers</a> configuration parameter.

  61.        </p></dd><dt><span class="term"><code class="option">-c <em class="replaceable"><code>name</code></em>=<em class="replaceable"><code>value</code></em></code></span></dt><dd><p>

  62.         Sets a named run-time parameter. The configuration parameters

  63.         supported by <span class="productname">PostgreSQL</span> are

  64.         described in <a class="xref" href="runtime-config.html" title="Chapter 19. Server Configuration">Chapter 19</a>. Most of the

  65.         other command line options are in fact short forms of such a

  66.         parameter assignment.  <code class="option">-c</code> can appear multiple times

  67.         to set multiple parameters.

  68.        </p></dd><dt><span class="term"><code class="option">-C <em class="replaceable"><code>name</code></em></code></span></dt><dd><p>

  69.         Prints the value of the named run-time parameter, and exits.

  70.         (See the <code class="option">-c</code> option above for details.)  This can

  71.         be used on a running server, and returns values from

  72.         <code class="filename">postgresql.conf</code>, modified by any parameters

  73.         supplied in this invocation.  It does not reflect parameters

  74.         supplied when the cluster was started.

  75.        </p><p>

  76.         This option is meant for other programs that interact with a server

  77.         instance, such as <a class="xref" href="app-pg-ctl.html" title="pg_ctl"><span class="refentrytitle"><span class="application">pg_ctl</span></span></a>, to query configuration

  78.         parameter values.  User-facing applications should instead use <a class="xref" href="sql-show.html" title="SHOW"><span class="refentrytitle">SHOW</span></a> or the <code class="structname">pg_settings</code> view.

  79.        </p></dd><dt><span class="term"><code class="option">-d <em class="replaceable"><code>debug-level</code></em></code></span></dt><dd><p>

  80.         Sets the debug level.  The higher this value is set, the more

  81.         debugging output is written to the server log.  Values are

  82.         from 1 to 5.  It is also possible to pass <code class="literal">-d

  83.         0</code> for a specific session, which will prevent the

  84.         server log level of the parent <code class="command">postgres</code> process from being

  85.         propagated to this session.

  86.        </p></dd><dt><span class="term"><code class="option">-D <em class="replaceable"><code>datadir</code></em></code></span></dt><dd><p>

  87.         Specifies the file system location of the database

  88.         configuration files.  See

  89.         <a class="xref" href="runtime-config-file-locations.html" title="19.2. File Locations">Section 19.2</a> for details.

  90.        </p></dd><dt><span class="term"><code class="option">-e</code></span></dt><dd><p>

  91.         Sets the default date style to <span class="quote">“<span class="quote">European</span>”</span>, that is

  92.         <code class="literal">DMY</code> ordering of input date fields.  This also causes

  93.         the day to be printed before the month in certain date output formats.

  94.         See <a class="xref" href="datatype-datetime.html" title="8.5. Date/Time Types">Section 8.5</a> for more information.

  95.        </p></dd><dt><span class="term"><code class="option">-F</code></span></dt><dd><p>

  96.         Disables <code class="function">fsync</code> calls for improved

  97.         performance, at the risk of data corruption in the event of a

  98.         system crash.  Specifying this option is equivalent to

  99.         disabling the <a class="xref" href="runtime-config-wal.html#GUC-FSYNC">fsync</a> configuration

  100.         parameter. Read the detailed documentation before using this!

  101.        </p></dd><dt><span class="term"><code class="option">-h <em class="replaceable"><code>hostname</code></em></code></span></dt><dd><p>

  102.         Specifies the IP host name or address on which

  103.         <code class="command">postgres</code> is to listen for TCP/IP

  104.         connections from client applications.  The value can also be a

  105.         comma-separated list of addresses, or <code class="literal">*</code> to specify

  106.         listening on all available interfaces.  An empty value

  107.         specifies not listening on any IP addresses, in which case

  108.         only Unix-domain sockets can be used to connect to the

  109.         server.  Defaults to listening only on

  110.         <span class="systemitem">localhost</span>.

  111.         Specifying this option is equivalent to setting the <a class="xref" href="runtime-config-connection.html#GUC-LISTEN-ADDRESSES">listen_addresses</a> configuration parameter.

  112.        </p></dd><dt><span class="term"><code class="option">-i</code></span></dt><dd><p>

  113.         Allows remote clients to connect via TCP/IP (Internet domain)

  114.         connections.  Without this option, only local connections are

  115.         accepted.  This option is equivalent to setting

  116.         <code class="varname">listen_addresses</code> to <code class="literal">*</code> in

  117.         <code class="filename">postgresql.conf</code> or via <code class="option">-h</code>.

  118.        </p><p>

  119.         This option is deprecated since it does not allow access to the

  120.         full functionality of <a class="xref" href="runtime-config-connection.html#GUC-LISTEN-ADDRESSES">listen_addresses</a>.

  121.         It's usually better to set <code class="varname">listen_addresses</code> directly.

  122.        </p></dd><dt><span class="term"><code class="option">-k <em class="replaceable"><code>directory</code></em></code></span></dt><dd><p>

  123.         Specifies the directory of the Unix-domain socket on which

  124.         <code class="command">postgres</code> is to listen for

  125.         connections from client applications.  The value can also be a

  126.         comma-separated list of directories.  An empty value

  127.         specifies not listening on any Unix-domain sockets, in which case

  128.         only TCP/IP sockets can be used to connect to the server.

  129.         The default value is normally

  130.         <code class="filename">/tmp</code>, but that can be changed at build time.

  131.         Specifying this option is equivalent to setting the <a class="xref" href="runtime-config-connection.html#GUC-UNIX-SOCKET-DIRECTORIES">unix_socket_directories</a> configuration parameter.

  132.        </p></dd><dt><span class="term"><code class="option">-l</code></span></dt><dd><p>

  133.         Enables secure connections using <acronym class="acronym">SSL</acronym>.

  134.         <span class="productname">PostgreSQL</span> must have been compiled with

  135.         support for <acronym class="acronym">SSL</acronym> for this option to be

  136.         available. For more information on using <acronym class="acronym">SSL</acronym>,

  137.         refer to <a class="xref" href="ssl-tcp.html" title="18.9. Secure TCP/IP Connections with SSL">Section 18.9</a>.

  138.        </p></dd><dt><span class="term"><code class="option">-N <em class="replaceable"><code>max-connections</code></em></code></span></dt><dd><p>

  139.         Sets the maximum number of client connections that this

  140.         server will accept.  The default value of this parameter is chosen

  141.         automatically by <span class="application">initdb</span>.

  142.         Specifying this option is equivalent to setting the

  143.         <a class="xref" href="runtime-config-connection.html#GUC-MAX-CONNECTIONS">max_connections</a> configuration parameter.

  144.        </p></dd><dt><span class="term"><code class="option">-o <em class="replaceable"><code>extra-options</code></em></code></span></dt><dd><p>

  145.         The command-line-style arguments specified in <em class="replaceable"><code>extra-options</code></em> are passed to

  146.         all server processes started by this

  147.         <code class="command">postgres</code> process.

  148.        </p><p>

  149.         Spaces within <em class="replaceable"><code>extra-options</code></em> are

  150.         considered to separate arguments, unless escaped with a backslash

  151.         (<code class="literal">\</code>); write <code class="literal">\\</code> to represent a literal

  152.         backslash.  Multiple arguments can also be specified via multiple

  153.         uses of <code class="option">-o</code>.

  154.        </p><p>

  155.         The use of this option is obsolete; all command-line options

  156.         for server processes can be specified directly on the

  157.         <code class="command">postgres</code> command line.

  158.        </p></dd><dt><span class="term"><code class="option">-p <em class="replaceable"><code>port</code></em></code></span></dt><dd><p>

  159.         Specifies the TCP/IP port or local Unix domain socket file

  160.         extension on which <code class="command">postgres</code>

  161.         is to listen for connections from client applications.

  162.         Defaults to the value of the <code class="envar">PGPORT</code> environment

  163.         variable, or if <code class="envar">PGPORT</code> is not set, then

  164.         defaults to the value established during compilation (normally

  165.         5432).  If you specify a port other than the default port,

  166.         then all client applications must specify the same port using

  167.         either command-line options or <code class="envar">PGPORT</code>.

  168.        </p></dd><dt><span class="term"><code class="option">-s</code></span></dt><dd><p>

  169.         Print time information and other statistics at the end of each command.

  170.         This is useful for benchmarking or for use in tuning the number of

  171.         buffers.

  172.        </p></dd><dt><span class="term"><code class="option">-S</code> <em class="replaceable"><code>work-mem</code></em></span></dt><dd><p>

  173.         Specifies the amount of memory to be used by internal sorts and hashes

  174.         before resorting to temporary disk files.  See the description of the

  175.         <code class="varname">work_mem</code> configuration parameter in <a class="xref" href="runtime-config-resource.html#RUNTIME-CONFIG-RESOURCE-MEMORY" title="19.4.1. Memory">Section 19.4.1</a>.

  176.        </p></dd><dt><span class="term"><code class="option">-V</code><br /></span><span class="term"><code class="option">--version</code></span></dt><dd><p>

  177.         Print the <span class="application">postgres</span> version and exit.

  178.        </p></dd><dt><span class="term"><code class="option">--<em class="replaceable"><code>name</code></em>=<em class="replaceable"><code>value</code></em></code></span></dt><dd><p>

  179.         Sets a named run-time parameter; a shorter form of

  180.         <code class="option">-c</code>.

  181.        </p></dd><dt><span class="term"><code class="option">--describe-config</code></span></dt><dd><p>

  182.         This option dumps out the server's internal configuration variables,

  183.         descriptions, and defaults in tab-delimited <code class="command">COPY</code> format.

  184.         It is designed primarily for use by administration tools.

  185.        </p></dd><dt><span class="term"><code class="option">-?</code><br /></span><span class="term"><code class="option">--help</code></span></dt><dd><p>

  186.         Show help about <span class="application">postgres</span> command line

  187.         arguments, and exit.

  188.        </p></dd></dl></div></div><div class="refsect2" id="id-1.9.5.14.6.4"><h3>Semi-Internal Options</h3><p>

  189.      The options described here are used

  190.      mainly for debugging purposes, and in some cases to assist with

  191.      recovery of severely damaged databases. There should be no reason

  192.      to use them in a production database setup.  They are listed

  193.      here only for use by <span class="productname">PostgreSQL</span>

  194.      system developers.  Furthermore, these options might

  195.      change or be removed in a future release without notice.

  196.     </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">-f</code> <code class="literal">{ s | i | o | b | t | n | m | h }</code></span></dt><dd><p>

  197.         Forbids the use of particular scan and join methods:

  198.         <code class="literal">s</code> and <code class="literal">i</code>

  199.         disable sequential and index scans respectively,

  200.         <code class="literal">o</code>, <code class="literal">b</code> and <code class="literal">t</code>

  201.         disable index-only scans, bitmap index scans, and TID scans

  202.         respectively, while

  203.         <code class="literal">n</code>, <code class="literal">m</code>, and <code class="literal">h</code>

  204.         disable nested-loop, merge and hash joins respectively.

  205.        </p><p>

  206.         Neither sequential scans nor nested-loop joins can be disabled

  207.         completely; the <code class="literal">-fs</code> and

  208.         <code class="literal">-fn</code> options simply discourage the optimizer

  209.         from using those plan types if it has any other alternative.

  210.        </p></dd><dt><span class="term"><code class="option">-n</code></span></dt><dd><p>

  211.         This option is for debugging problems that cause a server

  212.         process to die abnormally.  The ordinary strategy in this

  213.         situation is to notify all other server processes that they

  214.         must terminate and then reinitialize the shared memory and

  215.         semaphores.  This is because an errant server process could

  216.         have corrupted some shared state before terminating.  This

  217.         option specifies that <code class="command">postgres</code> will

  218.         not reinitialize shared data structures.  A knowledgeable

  219.         system programmer can then use a debugger to examine shared

  220.         memory and semaphore state.

  221.        </p></dd><dt><span class="term"><code class="option">-O</code></span></dt><dd><p>

  222.         Allows the structure of system tables to be modified.  This is

  223.         used by <code class="command">initdb</code>.

  224.        </p></dd><dt><span class="term"><code class="option">-P</code></span></dt><dd><p>

  225.         Ignore system indexes when reading system tables, but still update

  226.         the indexes when modifying the tables.  This is useful when

  227.         recovering from damaged system indexes.

  228.        </p></dd><dt><span class="term"><code class="option">-t</code> <code class="literal">pa[rser] | pl[anner] | e[xecutor]</code></span></dt><dd><p>

  229.         Print timing statistics for each query relating to each of the

  230.         major system modules.  This option cannot be used together

  231.         with the <code class="option">-s</code> option.

  232.        </p></dd><dt><span class="term"><code class="option">-T</code></span></dt><dd><p>

  233.         This option is for debugging problems that cause a server

  234.         process to die abnormally.  The ordinary strategy in this

  235.         situation is to notify all other server processes that they

  236.         must terminate and then reinitialize the shared memory and

  237.         semaphores.  This is because an errant server process could

  238.         have corrupted some shared state before terminating.  This

  239.         option specifies that <code class="command">postgres</code> will

  240.         stop all other server processes by sending the signal

  241.         <code class="literal">SIGSTOP</code>, but will not cause them to

  242.         terminate.  This permits system programmers to collect core

  243.         dumps from all server processes by hand.

  244.        </p></dd><dt><span class="term"><code class="option">-v</code> <em class="replaceable"><code>protocol</code></em></span></dt><dd><p>

  245.         Specifies the version number of the frontend/backend protocol

  246.         to be used for a particular session.  This option is for

  247.         internal use only.

  248.        </p></dd><dt><span class="term"><code class="option">-W</code> <em class="replaceable"><code>seconds</code></em></span></dt><dd><p>

  249.         A delay of this many seconds occurs when a new server process

  250.         is started, after it conducts the authentication procedure.

  251.         This is intended to give an opportunity to attach to the

  252.         server process with a debugger.

  253.        </p></dd></dl></div></div><div class="refsect2" id="id-1.9.5.14.6.5"><h3>Options for Single-User Mode</h3><a id="id-1.9.5.14.6.5.2" class="indexterm"></a><p>

  254.      The following options only apply to the single-user mode

  255.      (see <a class="xref" href="app-postgres.html#APP-POSTGRES-SINGLE-USER" title="Single-User Mode">Single-User Mode</a>).

  256.     </p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="option">--single</code></span></dt><dd><p>

  257.         Selects the single-user mode.  This must be the first argument

  258.         on the command line.

  259.        </p></dd><dt><span class="term"><em class="replaceable"><code>database</code></em></span></dt><dd><p>

  260.         Specifies the name of the database to be accessed.  This must be

  261.         the last argument on the command line.  If it is

  262.         omitted it defaults to the user name.

  263.        </p></dd><dt><span class="term"><code class="option">-E</code></span></dt><dd><p>

  264.         Echo all commands to standard output before executing them.

  265.        </p></dd><dt><span class="term"><code class="option">-j</code></span></dt><dd><p>

  266.         Use semicolon followed by two newlines, rather than just newline,

  267.         as the command entry terminator.

  268.        </p></dd><dt><span class="term"><code class="option">-r</code> <em class="replaceable"><code>filename</code></em></span></dt><dd><p>

  269.         Send all server log output to <em class="replaceable"><code>filename</code></em>.  This option is only

  270.         honored when supplied as a command-line option.

  271.        </p></dd></dl></div></div></div><div class="refsect1" id="id-1.9.5.14.7"><h2>Environment</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="envar">PGCLIENTENCODING</code></span></dt><dd><p>

  272.       Default character encoding used by clients.  (The clients can

  273.       override this individually.)  This value can also be set in the

  274.       configuration file.

  275.      </p></dd><dt><span class="term"><code class="envar">PGDATA</code></span></dt><dd><p>

  276.       Default data directory location

  277.      </p></dd><dt><span class="term"><code class="envar">PGDATESTYLE</code></span></dt><dd><p>

  278.       Default value of the <a class="xref" href="runtime-config-client.html#GUC-DATESTYLE">DateStyle</a> run-time

  279.       parameter.  (The use of this environment variable is deprecated.)

  280.      </p></dd><dt><span class="term"><code class="envar">PGPORT</code></span></dt><dd><p>

  281.       Default port number (preferably set in the configuration file)

  282.      </p></dd></dl></div></div><div class="refsect1" id="id-1.9.5.14.8"><h2>Diagnostics</h2><p>

  283.     A failure message mentioning <code class="literal">semget</code> or

  284.     <code class="literal">shmget</code> probably indicates you need to configure your

  285.     kernel to provide adequate shared memory and semaphores.  For more

  286.     discussion see <a class="xref" href="kernel-resources.html" title="18.4. Managing Kernel Resources">Section 18.4</a>.  You might be able

  287.     to postpone reconfiguring your kernel by decreasing <a class="xref" href="runtime-config-resource.html#GUC-SHARED-BUFFERS">shared_buffers</a> to reduce the shared memory

  288.     consumption of <span class="productname">PostgreSQL</span>, and/or by reducing

  289.     <a class="xref" href="runtime-config-connection.html#GUC-MAX-CONNECTIONS">max_connections</a> to reduce the semaphore

  290.     consumption.

  291.    </p><p>

  292.     A failure message suggesting that another server is already running

  293.     should be checked carefully, for example by using the command

  294. </p><pre class="screen">

  295. <code class="prompt">$</code> <strong class="userinput"><code>ps ax | grep postgres</code></strong>

  296. </pre><p>

  297.         or

  298. </p><pre class="screen">

  299. <code class="prompt">$</code> <strong class="userinput"><code>ps -ef | grep postgres</code></strong>

  300. </pre><p>

  301.     depending on your system.  If you are certain that no conflicting

  302.     server is running, you can remove the lock file mentioned in the

  303.     message and try again.

  304.    </p><p>

  305.     A failure message indicating inability to bind to a port might

  306.     indicate that that port is already in use by some

  307.     non-<span class="productname">PostgreSQL</span> process.  You might also

  308.     get this error if you terminate <code class="command">postgres</code>

  309.     and immediately restart it using the same port; in this case, you

  310.     must simply wait a few seconds until the operating system closes

  311.     the port before trying again.  Finally, you might get this error if

  312.     you specify a port number that your operating system considers to

  313.     be reserved.  For example, many versions of Unix consider port

  314.     numbers under 1024 to be <span class="quote">“<span class="quote">trusted</span>”</span> and only permit

  315.     the Unix superuser to access them.

  316.    </p></div><div class="refsect1" id="id-1.9.5.14.9"><h2>Notes</h2><p>

  317.    The utility command <a class="xref" href="app-pg-ctl.html" title="pg_ctl"><span class="refentrytitle"><span class="application">pg_ctl</span></span></a> can be used to

  318.    start and shut down the <code class="command">postgres</code> server

  319.    safely and comfortably.

  320.   </p><p>

  321.    If at all possible, <span class="emphasis"><em>do not</em></span> use

  322.    <code class="literal">SIGKILL</code> to kill the main

  323.    <code class="command">postgres</code> server.  Doing so will prevent

  324.    <code class="command">postgres</code> from freeing the system

  325.    resources (e.g., shared memory and semaphores) that it holds before

  326.    terminating.  This might cause problems for starting a fresh

  327.    <code class="command">postgres</code> run.

  328.   </p><p>

  329.    To terminate the <code class="command">postgres</code> server normally, the

  330.    signals <code class="literal">SIGTERM</code>, <code class="literal">SIGINT</code>, or

  331.    <code class="literal">SIGQUIT</code> can be used.  The first will wait for

  332.    all clients to terminate before quitting, the second will

  333.    forcefully disconnect all clients, and the third will quit

  334.    immediately without proper shutdown, resulting in a recovery run

  335.    during restart.

  336.   </p><p>

  337.    The <code class="literal">SIGHUP</code> signal will reload

  338.    the server configuration files.  It is also possible to send

  339.    <code class="literal">SIGHUP</code> to an individual server process, but that

  340.    is usually not sensible.

  341.   </p><p>

  342.    To cancel a running query, send the <code class="literal">SIGINT</code> signal

  343.    to the process running that command. To terminate a backend process

  344.    cleanly, send <code class="literal">SIGTERM</code> to that process. See

  345.    also <code class="function">pg_cancel_backend</code> and <code class="function">pg_terminate_backend</code>

  346.    in <a class="xref" href="functions-admin.html#FUNCTIONS-ADMIN-SIGNAL" title="9.26.2. Server Signaling Functions">Section 9.26.2</a> for the SQL-callable equivalents

  347.    of these two actions.

  348.   </p><p>

  349.    The <code class="command">postgres</code> server uses <code class="literal">SIGQUIT</code>

  350.    to tell subordinate server processes to terminate without normal

  351.    cleanup.

  352.    This signal <span class="emphasis"><em>should not</em></span> be used by users.  It

  353.    is also unwise to send <code class="literal">SIGKILL</code> to a server

  354.    process — the main <code class="command">postgres</code> process will

  355.    interpret this as a crash and will force all the sibling processes

  356.    to quit as part of its standard crash-recovery procedure.

  357.   </p></div><div class="refsect1" id="APP-POSTGRES-BUGS"><h2>Bugs</h2><p>

  358.    The <code class="option">--</code> options will not work on <span class="systemitem">FreeBSD</span> or <span class="systemitem">OpenBSD</span>.

  359.    Use <code class="option">-c</code> instead. This is a bug in the affected operating

  360.    systems; a future release of <span class="productname">PostgreSQL</span>

  361.    will provide a workaround if this is not fixed.

  362.   </p></div><div class="refsect1" id="APP-POSTGRES-SINGLE-USER"><h2>Single-User Mode</h2><p>

  363.     To start a single-user mode server, use a command like

  364. </p><pre class="screen">

  365. <strong class="userinput"><code>postgres --single -D /usr/local/pgsql/data <em class="replaceable"><code>other-options</code></em> my_database</code></strong>

  366. </pre><p>

  367.     Provide the correct path to the database directory with <code class="option">-D</code>, or

  368.     make sure that the environment variable <code class="envar">PGDATA</code> is set.

  369.     Also specify the name of the particular database you want to work in.

  370.    </p><p>

  371.     Normally, the single-user mode server treats newline as the command

  372.     entry terminator; there is no intelligence about semicolons,

  373.     as there is in <span class="application">psql</span>.  To continue a command

  374.     across multiple lines, you must type backslash just before each

  375.     newline except the last one.  The backslash and adjacent newline are

  376.     both dropped from the input command.  Note that this will happen even

  377.     when within a string literal or comment.

  378.    </p><p>

  379.     But if you use the <code class="option">-j</code> command line switch, a single newline

  380.     does not terminate command entry; instead, the sequence

  381.     semicolon-newline-newline does.  That is, type a semicolon immediately

  382.     followed by a completely empty line.  Backslash-newline is not

  383.     treated specially in this mode.  Again, there is no intelligence about

  384.     such a sequence appearing within a string literal or comment.

  385.    </p><p>

  386.     In either input mode, if you type a semicolon that is not just before or

  387.     part of a command entry terminator, it is considered a command separator.

  388.     When you do type a command entry terminator, the multiple statements

  389.     you've entered will be executed as a single transaction.

  390.    </p><p>

  391.     To quit the session, type <acronym class="acronym">EOF</acronym>

  392.     (<span class="keycap"><strong>Control</strong></span>+<span class="keycap"><strong>D</strong></span>, usually).

  393.     If you've entered any text since the last command entry terminator,

  394.     then <acronym class="acronym">EOF</acronym> will be taken as a command entry terminator,

  395.     and another <acronym class="acronym">EOF</acronym> will be needed to exit.

  396.    </p><p>

  397.     Note that the single-user mode server does not provide sophisticated

  398.     line-editing features (no command history, for example).

  399.     Single-user mode also does not do any background processing, such as

  400.     automatic checkpoints or replication.

  401.    </p></div><div class="refsect1" id="APP-POSTGRES-EXAMPLES"><h2>Examples</h2><p>

  402.    To start <code class="command">postgres</code> in the background

  403.    using default values, type:

  404. 

  405. </p><pre class="screen">

  406. <code class="prompt">$</code> <strong class="userinput"><code>nohup postgres &gt;logfile 2&gt;&amp;1 &lt;/dev/null &amp;</code></strong>

  407. </pre><p>

  408.   </p><p>

  409.    To start <code class="command">postgres</code> with a specific

  410.    port, e.g. 1234:

  411. </p><pre class="screen">

  412. <code class="prompt">$</code> <strong class="userinput"><code>postgres -p 1234</code></strong>

  413. </pre><p>

  414.    To connect to this server using <span class="application">psql</span>, specify this port with the -p option:

  415. </p><pre class="screen">

  416. <code class="prompt">$</code> <strong class="userinput"><code>psql -p 1234</code></strong>

  417. </pre><p>

  418.    or set the environment variable <code class="envar">PGPORT</code>:

  419. </p><pre class="screen">

  420. <code class="prompt">$</code> <strong class="userinput"><code>export PGPORT=1234</code></strong>

  421. <code class="prompt">$</code> <strong class="userinput"><code>psql</code></strong>

  422. </pre><p>

  423.   </p><p>

  424.    Named run-time parameters can be set in either of these styles:

  425. </p><pre class="screen">

  426. <code class="prompt">$</code> <strong class="userinput"><code>postgres -c work_mem=1234</code></strong>

  427. <code class="prompt">$</code> <strong class="userinput"><code>postgres --work-mem=1234</code></strong>

  428. </pre><p>

  429.    Either form overrides whatever setting might exist for

  430.    <code class="varname">work_mem</code> in <code class="filename">postgresql.conf</code>.  Notice that

  431.    underscores in parameter names can be written as either underscore

  432.    or dash on the command line.  Except for short-term experiments,

  433.    it's probably better practice to edit the setting in

  434.    <code class="filename">postgresql.conf</code> than to rely on a command-line switch

  435.    to set a parameter.

  436.   </p></div><div class="refsect1" id="id-1.9.5.14.13"><h2>See Also</h2><p>

  437.    <a class="xref" href="app-initdb.html" title="initdb"><span class="refentrytitle">initdb</span></a>,

  438.    <a class="xref" href="app-pg-ctl.html" title="pg_ctl"><span class="refentrytitle"><span class="application">pg_ctl</span></span></a>

  439.   </p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="pgwaldump.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="reference-server.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="app-postmaster.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top"><span class="application">pg_waldump</span> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> <span class="application">postmaster</span></td></tr></table></div></body></html>
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