#!/usr/bin/perl -wT

# multiversion/cluster aware pg_ctl wrapper; this also supplies the correct
# configuration parameters to 'start', and makes sure that postgres really
# stops on 'stop'.
#
# (C) 2005-2009 Martin Pitt <mpitt@debian.org>
# (C) 2009 Cyril Bouthors <cyril@bouthors.org>
# (C) 2013-2019 Christoph Berg <myon@debian.org>
#
#  This program is free software; you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation; either version 2 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.

use strict;
use warnings;
use Getopt::Long;
use POSIX qw/setsid dup2 :sys_wait_h/;
use PgCommon;
use Fcntl qw(SEEK_SET O_RDWR O_CREAT O_EXCL);
use POSIX qw(lchown);

my ($version, $cluster, $pg_ctl, $force);
my (@postgres_auxoptions, @pg_ctl_opts_from_cli);
my (%postgresql_conf, %info);
my $mode = 'fast'; # default shutdown mode
my $foreground = 0; # don't daemonize, use postgres instead of pg_ctl
my $stdlog = 0; # when run in foreground, still log to the default logfile

# untaint environment
$ENV{'PATH'} = '/sbin:/bin:/usr/sbin:/usr/bin';
delete @ENV{'IFS', 'CDPATH', 'ENV', 'BASH_ENV'};
chdir '/';

# If a pid file is already present, delete it if it is stale/invalid, or exit
# with a notice if it belongs to an already running postgres.
sub start_check_pid_file {
    my $pidfile = $info{'pgdata'}.'/postmaster.pid';
    if (PgCommon::check_pidfile_running $pidfile) {
        print "Cluster is already running.\n";
        exit 2;
    }

    # Remove invalid or stale PID file
    if (-e $pidfile) {
	unlink $pidfile;
	print "Removed stale pid file.\n";
    }
}

# Check if a pid file is not present or it is invalid. If so, clean up/abort.
sub stop_check_pid_file {
    my $pidfile = $info{'pgdata'}.'/postmaster.pid';
    my $pid = read_pidfile $pidfile;
    return if (defined $pid && PgCommon::check_pidfile_running $pidfile); 
    if ($info{'running'}) {
	error 'pid file is invalid, please manually kill the stale server process.';
    }

    # Remove invalid or stale PID file
    if (-e $pidfile) {
	unlink $pidfile;
	print "Removed stale pid file.\n";
    }
    print "Cluster is not running.\n";
    exit 2;
}

# check if a cluster reliably connects or fails
# Arguments: <version> <cluster> <port> <socket dir>
sub cluster_port_ready {
    my ($v, $c, $p, $sd) = @_;
    my $psql = get_program_path 'psql', $v;
    error 'cluster_port_ready: could not find psql binary' unless $psql;
    my $n = 0;
    my $result = 0;


    # probe until we get three successful or failed connections in a row
    $ENV{'PGPASSWORD'} = 'foo'; # prevent hangs if superuser cannot connect without password
    my $out;
    while ($n < ($result ? 10 : 3)) {
        select undef, undef, undef, 0.5;
        $out = `$psql -h '$sd' --port $p -Xl 2>&1 >/dev/null`;

        if ($? == $result) {    
            $n++;
        } else {
            $n = 0;
        }
        $result = $?;
    }

    if ($out =~ 'FATAL:') {
	print STDERR "Warning: connection to the database failed, disabling startup checks:\n$out\n";
	return cluster_port_running $v, $c, $p;
    }
    return !$result;
}

sub start {
    start_check_pid_file;

    # check conflicting port
    if (cluster_port_running $version, $cluster, $info{'port'}) {
        my $sockdir = get_cluster_socketdir $version, $cluster;
        error("Port conflict: another instance is already running on $sockdir with port $info{'port'}");
    }

    # prepare environment (empty except for content of 'environment', and LANG)
    %ENV = read_cluster_conf_file $version, $cluster, 'environment';
    # set LANG so non-ascii chars in the server log are not replaced by '?' (affected are non-session contexts)
    unless (exists $ENV{LANG}) {
	my $lc_messages = PgCommon::get_conf_value $version, $cluster, 'postgresql.conf', 'lc_messages';
	$ENV{LANG} = $lc_messages if $lc_messages;
    }
    # 9.5 configures OOM killer using env vars
    if ($version >= 9.5) {
        $ENV{PG_OOM_ADJUST_FILE} = "/proc/self/oom_score_adj" unless (exists $ENV{PG_OOM_ADJUST_FILE});
        # PG_OOM_ADJUST_VALUE defaults to 0, but can be overridden here
    }

    my $postgres_opts = '';
    my $usd = $version >= 9.3 ? 'unix_socket_directories' : 'unix_socket_directory';
    if (!(PgCommon::get_conf_value $version, $cluster, 'postgresql.conf', $usd)) {
	$postgres_opts .= "-c $usd=\"$info{'socketdir'}\"";
    }

    my $cdir = $info{'configdir'};
    $postgres_opts .= " -c config_file=\"$cdir/postgresql.conf\"";
    if (!(PgCommon::get_conf_value $version, $cluster, 'postgresql.conf', 'hba_file')) {
        $postgres_opts .= " -c hba_file=\"$cdir/pg_hba.conf\"";
    }
    if (!(PgCommon::get_conf_value $version, $cluster, 'postgresql.conf', 'ident_file')) {
        $postgres_opts .= " -c ident_file=\"$cdir/pg_ident.conf\"";
    }

    if ((-d '/var/run/postgresql') && !defined (PgCommon::get_conf_value $version, $cluster, 'postgresql.conf', 'external_pid_file')) {
        # check whether /var/run/postgresql/ is writable as the cluster owner
        my $vrp_writable;
        if ($> == 0) {
            change_ugid $info{'owneruid'}, $info{'ownergid'};
            $vrp_writable = -w '/var/run/postgresql';
            $< = $> = 0;
            $( = $) = 0;
        } else {
            $vrp_writable = -w '/var/run/postgresql';
        }
        if ($vrp_writable) {
            $postgres_opts .= " -c external_pid_file=\"/var/run/postgresql/$version-$cluster.pid\"";
        }
    }

    $postgres_opts .= ' ' . (join ' ', @postgres_auxoptions);
    ($postgres_opts) = $postgres_opts =~ /(.*)/; # untaint

    if ($foreground) {
        if ($stdlog and $info{'logfile'}) {
            my $fd = POSIX::open($info{logfile}, POSIX::O_WRONLY|POSIX::O_APPEND|POSIX::O_CREAT) or error "Could not open logfile $info{logfile}";
            dup2($fd, 1);
            dup2($fd, 2);
        }
        my $postgres = get_program_path 'postgres', $version;
        error "Could not find postgres executable for version $version" unless ($postgres);
        exec '/bin/sh', '-c', "exec $postgres $postgres_opts" or
            error "Executing $postgres failed: $!"
    }

    # only supply or default logfile path when none is given explicitly in
    # postgresql.conf
    my @options = ($pg_ctl, 'start', '-D', $info{'pgdata'});
    my $logsize = 0;
    if ($info{'logfile'}) {
        push @options, ('-l', $info{'logfile'});
        # remember current size of the log
        $logsize = (stat $info{'logfile'})[7] || 0; # ignore stat errors
    }

    push @options, @pg_ctl_opts_from_cli if @pg_ctl_opts_from_cli;

    my %pg_ctl_opts_from_file = read_cluster_conf_file $version, $cluster, 'pg_ctl.conf';
    push @options, split(' ', $pg_ctl_opts_from_file{'pg_ctl_options'})
	if defined $pg_ctl_opts_from_file{'pg_ctl_options'} and $pg_ctl_opts_from_file{'pg_ctl_options'} ne '';

    push @options, ('-s', '-o', $postgres_opts);

    if (fork) {
        wait;
        if ($?) {
            my $exit = $? >> 8;
            print STDERR "Error: $pg_ctl @options exited with status $exit: $!\n";
            my $currlogsize = (stat $info{'logfile'})[7] if $info{'logfile'} && -r $info{'logfile'};
            if ($currlogsize) {
                open LOG, $info{'logfile'} or
                    error "Could not open log file " . $info{'logfile'};
                seek LOG, $logsize, SEEK_SET;
                print STDERR $_ while <LOG>;
            }
            exit $exit;
        }
    } else {
        setsid or error "could not start session: $!";
        if ($info{'logfile'}) {
            my $fd = POSIX::open($info{'logfile'}, POSIX::O_WRONLY|POSIX::O_APPEND|POSIX::O_CREAT) or error "Could not open logfile $info{'logfile'}";
            dup2($fd, 1);
            dup2($fd, 2);
        }
        exec $pg_ctl @options or error "could not exec $pg_ctl @options: $!";
    }

    # wait a bit until the socket exists
    my $success = 0;
    my $currlogsize = 0;
    my $pidfile = $info{'pgdata'}.'/postmaster.pid';
    for (my $attempt = 0; $attempt < 60; $attempt++) {
        select (undef, undef, undef, 0.5);
        $currlogsize = (stat $info{'logfile'})[7] if $info{'logfile'} && -r $info{'logfile'};
        if (cluster_port_running $version, $cluster, $info{'port'}) {
            $success = 1;
            last;
        }

        # if postgres wrote something, but the process does not exist any
        # more, there must be a problem and we can stop immediately
        last if ($currlogsize > $logsize && !PgCommon::check_pidfile_running $pidfile);
    }

    # OK, the server runs, now wait until it stabilized
    if ($success) {
	$success = cluster_port_ready $version, $cluster, $info{'port'}, $info{'socketdir'};
    }

    if (!$success) {
        if ($currlogsize) {
            print STDERR "The PostgreSQL server failed to start. Please check the log output:\n";
            open LOG, $info{'logfile'} or 
                error "Could not open log file " . $info{'logfile'};
            seek LOG, $logsize, SEEK_SET;
            print STDERR $_ while <LOG>;
        } else {
            print STDERR "The PostgreSQL server failed to start. Please check the log output.\n";
        }
        exit 1;
    }

    return 0;
}

sub stop {
    stop_check_pid_file;
    my $result = 1;

    my @options = ('stop', '-s', '-w', '-D', $info{'pgdata'});

    push @options, @pg_ctl_opts_from_cli if @pg_ctl_opts_from_cli;

    my %pg_ctl_opts_from_file = read_cluster_conf_file $version, $cluster, 'pg_ctl.conf';
    push @options, split(' ', $pg_ctl_opts_from_file{'pg_ctl_options'})
	if defined $pg_ctl_opts_from_file{'pg_ctl_options'} and $pg_ctl_opts_from_file{'pg_ctl_options'} ne '';

    if (!fork()) {
        close STDOUT;
        exec $pg_ctl, @options, '-m', ($force ? 'fast' : $mode);
    } else {
        wait;
        $result = $? >> 8;
    }

    # try harder if forced and server hasn't stopped yet
    if ($force and -f $info{'pgdata'}.'/postmaster.pid') {
        print "(does not shutdown gracefully, now stopping immediately)\n";
        $result = system $pg_ctl, @options, '-m', 'immediate';
    }

    # external_pid_file files are currently not removed by postgres itself
    if ($result == 0) {
	unlink "/var/run/postgresql/$version-$cluster.pid";
    }

    return $result;
}

sub restart {
    my $result;

    if ($info{'running'}) {
	$result = stop;
	return $result if $result;
    }
    return start;
}

sub reload {
    exec $pg_ctl, '-D', $info{'pgdata'}, '-s', @pg_ctl_opts_from_cli, 'reload';
}

sub status {
    exec $pg_ctl, '-D', $info{'pgdata'}, 'status';
}

sub promote {
    exec $pg_ctl, '-D', $info{'pgdata'}, '-s', @pg_ctl_opts_from_cli, 'promote';
}

#
# main
#

my ($skip_systemctl_redirect, $bindir);

exit 1 unless GetOptions ('o|options=s' => \@postgres_auxoptions,
    'f|force' => \$force,
    'm|mode=s' => \$mode,
    'foreground' => \$foreground,
    'skip-systemctl-redirect' => \$skip_systemctl_redirect,
    'stdlog' => \$stdlog,
    'bindir=s' => \$bindir,
);

if ($mode =~ /^(s(mart)?|f(ast)?|i(mmediate)?)$/) {
    $mode = $1; # untaint
} else {
    print "Invalid -m mode, valid are: smart fast immediate\n";
    exit 1;
}

($bindir) = $bindir =~ /^(\/.*)$/ if $bindir; # untaint

# accept both "version cluster action" and "version[-/]cluster action"
if (@ARGV < 2 or (@ARGV < 3 and $ARGV[0] !~ m![-/]!)) {
    print "Usage: $0 <version> <cluster> <action>\n";
    exit 1;
}

$version = shift @ARGV;
if ($version =~ m!^(\d+\.?\d)[-/](.+)!) {
    ($version, $cluster) = ($1, $2);
} else {
    $cluster = shift @ARGV;
}
my $action = shift @ARGV;

@pg_ctl_opts_from_cli=();
foreach my $argv (@ARGV) {
    push @pg_ctl_opts_from_cli, $argv =~ /(.*)/; # untaint
}

($version) = $version =~ /^(\d+\.?\d+)$/; # untaint
($cluster) = $cluster =~ /^([^'"\s]+)$/; # untaint
error 'specified cluster does not exist' unless $version && $cluster && cluster_exists $version, $cluster;
%info = cluster_info ($version, $cluster);

unless ($action eq 'stop') {
    # check if cluster is disabled in start.conf
    error 'Cluster is disabled' if $info{'start'} eq 'disabled';
}

unless (-d $info{'pgdata'} && defined $info{'owneruid'}) {
    error $info{'pgdata'} . ' is not accessible or does not exist';
}

# check that owner uid/gid is valid
unless (getpwuid $info{'owneruid'}) {
    error 'The cluster is owned by user id '.$info{'owneruid'}.' which does not exist'
}
unless (getgrgid $info{'ownergid'}) {
    error 'The cluster is owned by group id '.$info{'ownergid'}.' which does not exist'
}
# owneruid and configuid need to match, unless configuid is root
if (($< == 0 or $> == 0) and $info{'configuid'} != 0 and
        $info{'configuid'} != $info{'owneruid'}) {
    my $configowner = (getpwuid $info{'configuid'})[0] || "(unknown)";
    my $dataowner = (getpwuid $info{'owneruid'})[0];
    error "Config owner ($configowner:$info{configuid}) and data owner ($dataowner:$info{owneruid}) do not match, and config owner is not root";
}

# redirect the request through systemd
if (not $skip_systemctl_redirect and getppid() != 1 and # not run from init
    -d '/run/systemd/system' and not exists $ENV{_SYSTEMCTL_SKIP_REDIRECT} and # systemd is running
    not $foreground and # foreground operation not requested
    not exists $ENV{'PG_CLUSTER_CONF_ROOT'} and # not handling user clusters
    $action =~ /^(start|stop|restart)$/ # redirect only these actions
) {
    $action = $1; # untaint
    system 'systemctl', 'is-active', '-q', "postgresql\@$version-$cluster";
    my $unit_active = $? == 0;

    # if extra options are given, proceed with pg_ctlcluster with a warning
    if (@postgres_auxoptions != 0 or @pg_ctl_opts_from_cli != 0 or $bindir) { # extra options given
        print "Notice: extra pg_ctl/postgres options given, bypassing systemctl for $action operation\n" if (-t 1);
    # if we are root, redirect to systemctl unless stopping a cluster running outside systemd
    } elsif ($> == 0) {
        if ($action eq 'stop' and not $unit_active) {
            # proceed with pg_ctlcluster
        } else {
            #print "Redirecting $action request to systemctl\n" if (-t 1);
            system 'systemctl', $action, "postgresql\@$version-$cluster";
            exit $? >> 8;
            # program end
        }
    # as non-root, raise an error on restarting a cluster running from systemd
    } elsif ($action eq 'restart' and $unit_active) {
        error "cluster is running from systemd, can only restart it as root. Try instead:\n  sudo systemctl $action postgresql\@$version-$cluster";
        # program end
    # otherwise just raise a warning on start and restart as non-root
    } elsif (-t 1) {
        if ($action =~ /start/) {
            print "Warning: the cluster will not be running as a systemd service. Consider using systemctl:\n";
        } elsif ($unit_active) { # on stop, warn when running from systemd
            print "Warning: stopping the cluster using pg_ctlcluster will mark the systemd unit as failed. Consider using systemctl:\n";
        }
        print "  sudo systemctl $action postgresql\@$version-$cluster\n";
    }
}

# recreate missing standard log dir
if ($> == 0 && ! -e '/var/log/postgresql' &&
    $info{'logfile'} =~ m!^/var/log/postgresql!) {
    system 'install', '-d', '-m', '1775', '-o', 'root', '-g', 'postgres', '/var/log/postgresql';
}

# recreate missing log file
if ($action ne 'stop' && $info{'logfile'} && ! -e $info{'logfile'}) {
    if ($> == 0) { # drop privileges; this is important if logfile
        # was determined via an /etc/postgresql/.../log symlink
        change_ugid $info{'owneruid'}, $info{'ownergid'};
    }
    sysopen (L, $info{'logfile'}, O_RDWR|O_CREAT|O_EXCL) or
	error 'Could not create log file ' . $info{'logfile'};
    close L;
    chmod 0640, $info{'logfile'};
    $< = $> = 0; # will silently fail if we were not root before, that's intended
    $( = $) = 0;
    if ($info{'owneruid'} < 500) {
        my $g = (getgrnam 'adm')[2];
        lchown $info{'owneruid'}, $g, $info{'logfile'} if (defined $g);
    }
}

if ($action ne 'stop') {
    # recreate /var/run/postgresql while possibly still running as root
    if (! -d '/var/run/postgresql') {
        system 'install', '-d', '-m', 2775, '-o', 'postgres', '-g', 'postgres', '/var/run/postgresql';
    }

    # allow creating socket directories below /var/run/postgresql for any user
    if ($info{socketdir} =~ m!^(/var)/run/postgresql/[\w_.-]+$! and ! -d $info{socketdir}) {
        if (mkdir $info{socketdir}, 02775) { # don't use "install" here as it would allow stealing existing directories
            chown $info{owneruid}, $info{ownergid}, $info{socketdir};
        } else {
            error "Could not create $info{socketdir}: $!";
        }
    }

    # allow creating stats_temp_directory below /var/run/postgresql for any user
    if ($info{config}->{stats_temp_directory} and $info{config}->{stats_temp_directory}=~ m!^(/var)/run/postgresql/[\w_.-]+$! and ! -d $info{config}->{stats_temp_directory}) {
        if (mkdir $info{config}->{stats_temp_directory}, 0750) { # don't use "install" here as it would allow stealing existing directories
            chown $info{owneruid}, $info{ownergid}, $info{config}->{stats_temp_directory};
        } else {
            error "Could not create $info{config}->{stats_temp_directory}: $!";
        }
    }
}

if ($> == 0) {
    # have postgres start with increased OOM killer protection; 9.0 and
    # later has builtin support for resetting the adjustment of child processes
    if ($action eq 'start' and $version >= '9.0' and not $PgCommon::rpm) {
        if (-w '/proc/self/oom_score_adj') {
	    open F, '>/proc/self/oom_score_adj';
	    print F "-900\n";
	    close F;
	} 
    }

    change_ugid $info{'owneruid'}, $info{'ownergid'};
}

# we are running as the cluster owner now

if( $> != $info{'owneruid'} ) {
    error 'You must run this program as the cluster owner ('.
        (getpwuid $info{'owneruid'})[0].') or root';
}

# create socket directory (if it wasn't already created in /var/run/postgresql by the code above)
if ($action ne 'stop' && ! -d $info{socketdir}) {
    system 'install', '-d', '-m', 2775, $info{socketdir};
}

# create stats_temp_directory (if it wasn't already created in /var/run/postgresql by the code above)
if ($action ne 'stop' && $info{config}->{stats_temp_directory} && ! -d $info{config}->{stats_temp_directory}) {
    system 'install', '-d', '-m', 750, $info{config}->{stats_temp_directory};
}

$pg_ctl = $bindir ? "$bindir/pg_ctl" : get_program_path ('pg_ctl', $version);
error "Could not find pg_ctl executable for version $version" unless ($pg_ctl);

if ($action =~ /^(start|stop|restart|reload|status|promote)$/) {
    no strict 'refs';
    exit &$action;
} else {
    error 'Invalid action (must be one of: start stop restart reload status promote)';
}

__END__

=head1 NAME

pg_ctlcluster - start/stop/restart/reload a PostgreSQL cluster

=head1 SYNOPSIS

B<pg_ctlcluster> [I<options>] I<cluster-version> I<cluster-name> I<action> [B<--> I<pg_ctl options>]

where I<action> = B<start>|B<stop>|B<restart>|B<reload>|B<status>|B<promote>

=head1 DESCRIPTION

This program controls the B<postgres> server for a particular cluster. It
essentially wraps the L<pg_ctl(1)> command. It determines the cluster version
and data path and calls the right version of B<pg_ctl> with appropriate
configuration parameters and paths.

You have to start this program as the user who owns the database cluster or as
root.

To ease integration with B<systemd> operation, the alternative syntax
"B<pg_ctlcluster> I<version>B<->I<cluster> I<action>" is also supported.

=head1 ACTIONS

=over 4

=item B<start>

A log file for this specific cluster is created if it does not exist yet (by
default,
C</var/log/postgresql/postgresql->I<cluster-version>C<->I<cluster-name>C<.log>),
and a PostgreSQL server process (L<postgres(1)>) is started on it. Exits with
0 on success, with 2 if the server is already running, and with 1 on other
failure conditions.

=item B<stop>

Stops the L<postgres(1)> server of the given cluster. By default, "fast"
shutdown mode is used.

=item B<restart>

Stops the server if it is running and starts it (again).

=item B<reload>

Causes the configuration files to be re-read without a full shutdown of the
server.

=item B<status>

Checks whether a server is running. If it is, the PID and the command line
options that were used to invoke it are displayed.

=item B<promote>

Commands a running standby server to exit recovery and begin read-write
operations.

=back

=head1 OPTIONS

=over 4

=item B<-f>|B<--force>

For B<stop> and B<restart>, the "fast" mode is used which rolls back all active
transactions, disconnects clients immediately and thus shuts down cleanly. If
that does not work, shutdown is attempted again in "immediate" mode, which can
leave the cluster in an inconsistent state and thus will lead to a recovery run
at the next start. If this still does not help, the B<postgres> process is
killed.  Exits with 0 on success, with 2 if the server is not running, and with
1 on other failure conditions. This mode should only be used when the machine
is about to be shut down.

=item B<-m>|B<--mode> [B<smart>|B<fast>|B<immediate>]

Shutdown mode to use for B<stop> and B<restart> actions, default is B<fast>.
See pg_ctl(1) for documentation.

=item B<--foreground>

Start B<postgres> in foreground, without daemonizing via B<pg_ctl>.

=item B<--stdlog>

When B<--foreground> is in use, redirect stderr to the standard logfile in
C</var/log/postgresql/>.  (Default when not run in foreground.)

=item B<--skip-systemctl-redirect>

When running as root, B<pg_ctlcluster> redirects actions to B<systemctl> so
running clusters are properly supervised by B<systemd>. This option skips the
redirect; it is used in the B<postgresql@.service> unit file. The redirect is
also skipped if additional B<postgres> or B<pg_ctl> options are provided.

=item B<--bindir> I<directory>

Path to B<pg_ctl>.  (Default is C</usr/lib/postgresql/>I<version>C</bin>.)

=item B<-o>|B<--options> I<option>

Pass given I<option> as command line option to the C<postgres> process. It is
possible to specify B<-o> multiple times. See L<postgres(1)> for a
description of valid options.

=item I<pg_ctl options>

Pass given I<pg_ctl options> as command line options to B<pg_ctl>. See L<pg_ctl(1)>
for a description of valid options.

=back

=head1 FILES

=over 4

=item C</etc/postgresql/>I<cluster-version>C</>I<cluster-name>C</pg_ctl.conf>

This configuration file contains cluster specific options to be passed to
L<pg_ctl(1)>.

=item C</etc/postgresql/>I<cluster-version>C</>I<cluster-name>C</start.conf>

This configuration file controls the start/stop behavior of the cluster. See
section "STARTUP CONTROL" in L<pg_createcluster(8)> for details.

=back

=head1 BUGS

Changing the port number on startup using B<-o -p> will not work as it breaks
the checks for running clusters.

=head1 SEE ALSO

L<pg_createcluster(8)>, L<pg_ctl(1)>, L<pg_wrapper(1)>, L<pg_lsclusters(1)>,
L<postgres(1)>

=head1 AUTHOR

Martin Pitt L<E<lt>mpitt@debian.orgE<gt>>