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diff --git a/scripts/system/vyatta_check_domainname.pl b/scripts/system/vyatta_check_domainname.pl
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+++ b/scripts/system/vyatta_check_domainname.pl
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+#!/usr/bin/perl
+
+# **** License ****
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 as
+# published by the Free Software Foundation.
+#
+# 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.
+#
+# This code was originally developed by Vyatta, Inc.
+# Portions created by Vyatta are Copyright (C) 2010 Vyatta, Inc.
+# All Rights Reserved.
+#
+# **** End License ****
+
+use strict;
+use warnings;
+
+# Source: http://en.wikipedia.org/wiki/Domain_Name_System
+# Rules for forming domain names appear in RFC 1035, RFC 1123, and RFC 2181.
+# A domain name consists of one or more parts, technically called labels,
+# that are conventionally concatenated, and delimited by dots, 
+# such as example.com.
+#
+#  * The right-most label conveys the top-level domain; for example,
+#   the domain name www.example.com belongs to the top-level domain com.
+#  * The hierarchy of domains descends from right to left; each label to
+#    the left specifies a subdivision, or subdomain of the domain to the
+#    right. For example: the label example specifies a subdomain of the
+#    com domain, and www is a sub domain of example.com. This tree of
+#    subdivisions may have up to 127 levels.
+# 
+# * Each label may contain up to 63 characters. The full domain name may
+#   not exceed a total length of 253 characters in its external
+#   dotted-label specification.[10] In the internal binary
+#   representation of the DNS the maximum length requires 255 octets of
+#   storage.[3] In practice, some domain registries may have shorter
+#   limits.[citation needed]
+# 
+#  * DNS names may technically consist of any character representable in
+#    an octet. However, the allowed formulation of domain names in the
+#    DNS root zone, and most other sub domains, uses a preferred format
+#    and character set. The characters allowed in a label are a subset
+#    of the ASCII character set, and includes the characters a through
+#    z, A through Z, digits 0 through 9, and the hyphen. This rule is
+#    known as the LDH rule (letters, digits, hyphen). Domain names are
+#    interpreted in case-independent manner. Labels may not start or end
+#    with a hyphen.[11]
+
+foreach my $fqdn (@ARGV) {
+    die "$fqdn: full domain length exceeds 253 characters\n"
+	if length($fqdn) > 253;
+
+    my @label = split /\./, $fqdn;
+    die "$fqdn: domain name greater than 127 levels\n"
+	if ($#label > 127);
+
+    foreach my $label (@label) {
+	die "$label: invalid character in domain name\n"
+	    unless $label =~ /^[-0-9a-zA-H]+$/;
+
+	die "$label: label must not start or end with hyphen\n"
+	    if $label =~ /(^-)|(-$)/;
+
+	die "$label: domain name element greater than 63 characters\n"
+	    if (length($label) > 63);
+    }
+}
+