sub become_daemon
{
    my $dont_die = shift || 0;

    my ($child, $sig);

    $child = fork;
    if (defined $child)
    {
        exit 0 if $child;
    }
    else
    {
        $dont_die && return "Error in fork: $!";
        die "$0 died in fork: $!, dead";
    }

    #
    # First-generation child.
    #
    setpgrp;
    close(STDIN);
    close(STDOUT);
    close(STDERR);
    chdir '/';
    umask 0;
    for (qw(TSTP TTIN TTOU)) { $SIG{$_} = 'IGNORE' if (exists $SIG{$_}) }

    #
    # In case of SysV, re-spawn to avoid danger of re-acquiring a control
    # terminal. Now the child is not the pgrp leader.
    #
    $sig = $SIG{HUP};
    $SIG{HUP} = 'IGNORE';

    $child = fork;
    if (defined $child)
    {
        exit 0 if $child;
    }
    elsif ($child)
    {
        $dont_die && return "Error in (1st-generation child) fork: $!";
        die "$0 (1st-generation child) died in fork: $!, dead";
    }

    #
    # Restore HUP (which will probably be set later on, anyway) and return.
    #

    $SIG{HUP} = $sig;
    return;
}