listen_addresses (string)
      
      
         Specifies the TCP/IP address(es) on which the server is
         to listen for connections from client applications.
         The value takes the form of a comma-separated list of host names
         and/or numeric IP addresses.  The special entry *
         corresponds to all available IP interfaces.  The entry
         0.0.0.0 allows listening for all IPv4 addresses and
         :: allows listening for all IPv6 addresses.
         If the list is empty, the server does not listen on any IP interface
         at all, in which case only Unix-domain sockets can be used to connect
         to it.
         The default value is localhost,
         which allows only local TCP/IP “loopback” connections to be
         made.  While client authentication (Chapter 20) allows fine-grained control
         over who can access the server, listen_addresses
         controls which interfaces accept connection attempts, which
         can help prevent repeated malicious connection requests on
         insecure network interfaces.  This parameter can only be set
         at server start.
       
port (integer)
      
      The TCP port the server listens on; 5432 by default. Note that the same port number is used for all IP addresses the server listens on. This parameter can only be set at server start.
max_connections (integer)
      
      Determines the maximum number of concurrent connections to the database server. The default is typically 100 connections, but might be less if your kernel settings will not support it (as determined during initdb). This parameter can only be set at server start.
When running a standby server, you must set this parameter to the same or higher value than on the master server. Otherwise, queries will not be allowed in the standby server.
superuser_reserved_connections
      (integer)
      
      
        Determines the number of connection “slots” that
        are reserved for connections by PostgreSQL
        superusers.  At most max_connections
        connections can ever be active simultaneously.  Whenever the
        number of active concurrent connections is at least
        max_connections minus
        superuser_reserved_connections, new
        connections will be accepted only for superusers, and no
        new replication connections will be accepted.
       
        The default value is three connections. The value must be less
        than max_connections.
        This parameter can only be set at server start.
       
unix_socket_directories (string)
      
      
        Specifies the directory of the Unix-domain socket(s) on which the
        server is to listen for connections from client applications.
        Multiple sockets can be created by listing multiple directories
        separated by commas.  Whitespace between entries is
        ignored; surround a directory name with double quotes if you need
        to include whitespace or commas in the name.
        An empty value
        specifies not listening on any Unix-domain sockets, in which case
        only TCP/IP sockets can be used to connect to the server.
        The default value is normally
        /tmp, but that can be changed at build time.
        This parameter can only be set at server start.
       
        In addition to the socket file itself, which is named
        .s.PGSQL. where
        nnnnnnnn is the server's port number, an ordinary file
        named .s.PGSQL. will be
        created in each of the nnnn.lockunix_socket_directories directories.
        Neither file should ever be removed manually.
       
This parameter is irrelevant on Windows, which does not have Unix-domain sockets.
unix_socket_group (string)
      
      
        Sets the owning group of the Unix-domain socket(s).  (The owning
        user of the sockets is always the user that starts the
        server.)  In combination with the parameter
        unix_socket_permissions this can be used as
        an additional access control mechanism for Unix-domain connections.
        By default this is the empty string, which uses the default
        group of the server user.  This parameter can only be set at
        server start.
       
This parameter is irrelevant on Windows, which does not have Unix-domain sockets.
unix_socket_permissions (integer)
      
      
        Sets the access permissions of the Unix-domain socket(s).  Unix-domain
        sockets use the usual Unix file system permission set.
        The parameter value is expected to be a numeric mode
        specified in the format accepted by the
        chmod and umask
        system calls.  (To use the customary octal format the number
        must start with a 0 (zero).)
       
        The default permissions are 0777, meaning
        anyone can connect. Reasonable alternatives are
        0770 (only user and group, see also
        unix_socket_group) and 0700
        (only user). (Note that for a Unix-domain socket, only write
        permission matters, so there is no point in setting or revoking
        read or execute permissions.)
       
This access control mechanism is independent of the one described in Chapter 20.
This parameter can only be set at server start.
        This parameter is irrelevant on systems, notably Solaris as of Solaris
        10, that ignore socket permissions entirely.  There, one can achieve a
        similar effect by pointing unix_socket_directories to a
        directory having search permission limited to the desired audience.
        This parameter is also irrelevant on Windows, which does not have
        Unix-domain sockets.
       
bonjour (boolean)
      
      Enables advertising the server's existence via Bonjour. The default is off. This parameter can only be set at server start.
bonjour_name (string)
      
      
        Specifies the Bonjour service
        name.  The computer name is used if this parameter is set to the
        empty string '' (which is the default).  This parameter is
        ignored if the server was not compiled with
        Bonjour support.
        This parameter can only be set at server start.
       
tcp_keepalives_idle (integer)
      
      
        Specifies the amount of time with no network activity after which
        the operating system should send a TCP keepalive message to the client.
        If this value is specified without units, it is taken as seconds.
        A value of 0 (the default) selects the operating system's default.
        This parameter is supported only on systems that support
        TCP_KEEPIDLE or an equivalent socket option, and on
        Windows; on other systems, it must be zero.
        In sessions connected via a Unix-domain socket, this parameter is
        ignored and always reads as zero.
       
On Windows, setting a value of 0 will set this parameter to 2 hours, since Windows does not provide a way to read the system default value.
tcp_keepalives_interval (integer)
      
      
        Specifies the amount of time after which a TCP keepalive message
        that has not been acknowledged by the client should be retransmitted.
        If this value is specified without units, it is taken as seconds.
        A value of 0 (the default) selects the operating system's default.
        This parameter is supported only on systems that support
        TCP_KEEPINTVL or an equivalent socket option, and on
        Windows; on other systems, it must be zero.
        In sessions connected via a Unix-domain socket, this parameter is
        ignored and always reads as zero.
       
On Windows, setting a value of 0 will set this parameter to 1 second, since Windows does not provide a way to read the system default value.
tcp_keepalives_count (integer)
      
      
        Specifies the number of TCP keepalive messages that can be lost before
        the server's connection to the client is considered dead.
        A value of 0 (the default) selects the operating system's default.
        This parameter is supported only on systems that support
        TCP_KEEPCNT or an equivalent socket option;
        on other systems, it must be zero.
        In sessions connected via a Unix-domain socket, this parameter is
        ignored and always reads as zero.
       
This parameter is not supported on Windows, and must be zero.
tcp_user_timeout (integer)
      
      
        Specifies the amount of time that transmitted data may
        remain unacknowledged before the TCP connection is forcibly closed.
        If this value is specified without units, it is taken as milliseconds.
        A value of 0 (the default) selects the operating system's default.
        This parameter is supported only on systems that support
        TCP_USER_TIMEOUT; on other systems, it must be zero.
        In sessions connected via a Unix-domain socket, this parameter is
        ignored and always reads as zero.
       
This parameter is not supported on Windows, and must be zero.
authentication_timeout (integer)
      
      
      
      
        Maximum amount of time allowed to complete client authentication. If a
        would-be client has not completed the authentication protocol in
        this much time, the server closes the connection. This prevents
        hung clients from occupying a connection indefinitely.
        If this value is specified without units, it is taken as seconds.
        The default is one minute (1m).
        This parameter can only be set in the postgresql.conf
        file or on the server command line.
       
password_encryption (enum)
      
      
        When a password is specified in CREATE ROLE or
        ALTER ROLE, this parameter determines the algorithm
        to use to encrypt the password. The default value is md5,
        which stores the password as an MD5 hash (on is also
        accepted, as alias for md5). Setting this parameter to
        scram-sha-256 will encrypt the password with SCRAM-SHA-256.
       
Note that older clients might lack support for the SCRAM authentication mechanism, and hence not work with passwords encrypted with SCRAM-SHA-256. See Section 20.5 for more details.
krb_server_keyfile (string)
      
      
        Sets the location of the Kerberos server key file. See
        Section 20.6
        for details. This parameter can only be set in the
        postgresql.conf file or on the server command line.
       
krb_caseins_users (boolean)
      
      
        Sets whether GSSAPI user names should be treated
        case-insensitively.
        The default is off (case sensitive). This parameter can only be
        set in the postgresql.conf file or on the server command line.
       
db_user_namespace (boolean)
      
      
        This parameter enables per-database user names.  It is off by default.
        This parameter can only be set in the postgresql.conf
        file or on the server command line.
       
        If this is on, you should create users as username@dbname.
        When username is passed by a connecting client,
        @ and the database name are appended to the user
        name and that database-specific user name is looked up by the
        server. Note that when you create users with names containing
        @ within the SQL environment, you will need to
        quote the user name.
       
        With this parameter enabled, you can still create ordinary global
        users.  Simply append @ when specifying the user
        name in the client, e.g. joe@.  The @
        will be stripped off before the user name is looked up by the
        server.
       
        db_user_namespace causes the client's and
        server's user name representation to differ.
        Authentication checks are always done with the server's user name
        so authentication methods must be configured for the
        server's user name, not the client's.  Because
        md5 uses the user name as salt on both the
        client and server, md5 cannot be used with
        db_user_namespace.
       
This feature is intended as a temporary measure until a complete solution is found. At that time, this option will be removed.
See Section 18.9 for more information about setting up SSL.
ssl (boolean)
      
      
        Enables SSL connections.
        This parameter can only be set in the postgresql.conf
        file or on the server command line.
        The default is off.
       
ssl_ca_file (string)
      
      
        Specifies the name of the file containing the SSL server certificate
        authority (CA).
        Relative paths are relative to the data directory.
        This parameter can only be set in the postgresql.conf
        file or on the server command line.
        The default is empty, meaning no CA file is loaded,
        and client certificate verification is not performed.
       
ssl_cert_file (string)
      
      
        Specifies the name of the file containing the SSL server certificate.
        Relative paths are relative to the data directory.
        This parameter can only be set in the postgresql.conf
        file or on the server command line.
        The default is server.crt.
       
ssl_crl_file (string)
      
      
        Specifies the name of the file containing the SSL server certificate
        revocation list (CRL).
        Relative paths are relative to the data directory.
        This parameter can only be set in the postgresql.conf
        file or on the server command line.
        The default is empty, meaning no CRL file is loaded.
       
ssl_key_file (string)
      
      
        Specifies the name of the file containing the SSL server private key.
        Relative paths are relative to the data directory.
        This parameter can only be set in the postgresql.conf
        file or on the server command line.
        The default is server.key.
       
ssl_ciphers (string)
      
      
        Specifies a list of SSL cipher suites that are
        allowed to be used by SSL connections.  See the
        ciphers
        manual page in the OpenSSL package for the
        syntax of this setting and a list of supported values.  Only
        connections using TLS version 1.2 and lower are affected.  There is
        currently no setting that controls the cipher choices used by TLS
        version 1.3 connections.  The default value is
        HIGH:MEDIUM:+3DES:!aNULL.  The default is usually a
        reasonable choice unless you have specific security requirements.
       
        This parameter can only be set in the
        postgresql.conf file or on the server command
        line.
       
Explanation of the default value:
HIGH
            Cipher suites that use ciphers from HIGH group (e.g.,
            AES, Camellia, 3DES)
           
MEDIUM
            Cipher suites that use ciphers from MEDIUM group
            (e.g., RC4, SEED)
           
+3DES
            The OpenSSL default order for HIGH is problematic
            because it orders 3DES higher than AES128.  This is wrong because
            3DES offers less security than AES128, and it is also much
            slower.  +3DES reorders it after all other
            HIGH and MEDIUM ciphers.
           
!aNULLDisables anonymous cipher suites that do no authentication. Such cipher suites are vulnerable to man-in-the-middle attacks and therefore should not be used.
        Available cipher suite details will vary across OpenSSL versions.  Use
        the command
        openssl ciphers -v 'HIGH:MEDIUM:+3DES:!aNULL' to
        see actual details for the currently installed OpenSSL
        version.  Note that this list is filtered at run time based on the
        server key type.
       
ssl_prefer_server_ciphers (boolean)
      
      
        Specifies whether to use the server's SSL cipher preferences, rather
        than the client's.
        This parameter can only be set in the postgresql.conf
        file or on the server command line.
        The default is on.
       
Older PostgreSQL versions do not have this setting and always use the client's preferences. This setting is mainly for backward compatibility with those versions. Using the server's preferences is usually better because it is more likely that the server is appropriately configured.
ssl_ecdh_curve (string)
      
      
        Specifies the name of the curve to use in ECDH key
        exchange.  It needs to be supported by all clients that connect.
        It does not need to be the same curve used by the server's Elliptic
        Curve key.
        This parameter can only be set in the postgresql.conf
        file or on the server command line.
        The default is prime256v1.
       
        OpenSSL names for the most common curves are:
        prime256v1 (NIST P-256),
        secp384r1 (NIST P-384),
        secp521r1 (NIST P-521).
        The full list of available curves can be shown with the command
        openssl ecparam -list_curves.  Not all of them
        are usable in TLS though.
       
ssl_min_protocol_version (enum)
      
      
        Sets the minimum SSL/TLS protocol version to use.  Valid values are
        currently: TLSv1, TLSv1.1,
        TLSv1.2, TLSv1.3.  Older
        versions of the OpenSSL library do not
        support all values; an error will be raised if an unsupported setting
        is chosen.  Protocol versions before TLS 1.0, namely SSL version 2 and
        3, are always disabled.
       
        The default is TLSv1, mainly to support older
        versions of the OpenSSL library.  You might
        want to set this to a higher value if all software components can
        support the newer protocol versions.
       
ssl_max_protocol_version (enum)
      
      Sets the maximum SSL/TLS protocol version to use. Valid values are as for ssl_min_protocol_version, with addition of an empty string, which allows any protocol version. The default is to allow any version. Setting the maximum protocol version is mainly useful for testing or if some component has issues working with a newer protocol.
ssl_dh_params_file (string)
      
      
        Specifies the name of the file containing Diffie-Hellman parameters
        used for so-called ephemeral DH family of SSL ciphers. The default is
        empty, in which case compiled-in default DH parameters used. Using
        custom DH parameters reduces the exposure if an attacker manages to
        crack the well-known compiled-in DH parameters. You can create your own
        DH parameters file with the command
        openssl dhparam -out dhparams.pem 2048.
       
        This parameter can only be set in the postgresql.conf
        file or on the server command line.
       
ssl_passphrase_command (string)
      
      Sets an external command to be invoked when a passphrase for decrypting an SSL file such as a private key needs to be obtained. By default, this parameter is empty, which means the built-in prompting mechanism is used.
        The command must print the passphrase to the standard output and exit
        with code 0.  In the parameter value, %p is
        replaced by a prompt string.  (Write %% for a
        literal %.)  Note that the prompt string will
        probably contain whitespace, so be sure to quote adequately.  A single
        newline is stripped from the end of the output if present.
       
The command does not actually have to prompt the user for a passphrase. It can read it from a file, obtain it from a keychain facility, or similar. It is up to the user to make sure the chosen mechanism is adequately secure.
        This parameter can only be set in the postgresql.conf
        file or on the server command line.
       
ssl_passphrase_command_supports_reload (boolean)
      
      
        This parameter determines whether the passphrase command set by
        ssl_passphrase_command will also be called during a
        configuration reload if a key file needs a passphrase.  If this
        parameter is off (the default), then
        ssl_passphrase_command will be ignored during a
        reload and the SSL configuration will not be reloaded if a passphrase
        is needed.  That setting is appropriate for a command that requires a
        TTY for prompting, which might not be available when the server is
        running.  Setting this parameter to on might be appropriate if the
        passphrase is obtained from a file, for example.
       
        This parameter can only be set in the postgresql.conf
        file or on the server command line.