Central configuration for DHCP, DNS and Firewall

The script below doesn't directly answer your question, but as an example of the type of thing you can do with a perl script it may be useful. My setup is a building with 4 floors and a more restricted admin network. I use the script to add new machines as they arrive, recording the mac address and giving them an address that corresponds to the floor they're on. I use a $PWD/.floorN file to record the address so I can correctly increment. It also adds forward and reverse DNS records and IPAC-NG rules to record bandwidth. The script makes some assumptions as to the locations of files and the presence of some text in them to allow substitution for new records.

#!/usr/bin/perl -w
##################
($firstname, $secondname, $mac, $floor) = @ARGV;
$mac2 = lc $mac;
@requires = qw/firstname secondname mac/;
foreach(@requires) {
unless($$_) {
print "\$$_ not found, Please run this as $0 Firstname Secondname MAC floor\n";
exit;
}
}
unless($floor) { $floor = "0"; }
open(IPS, "+<.floor$floor");
$count = 1;
while (<IPS>) { $count++; }
print IPS "$firstname$secondname :$count\n";
print <<END;
adding to /etc/dhcp3/dhcpd.conf

host $firstname$secondname {
hardware ethernet $mac2;
fixed-address 10.0.1$floor.$count;
option routers 10.0.1$floor.254; 
}
END
open(ORIG, "/etc/dhcp3/dhcpd.conf");
@orig = <ORIG>; 
close(ORIG);
$add = <<END;
host $firstname$secondname {
hardware ethernet $mac2;
fixed-address 10.0.1$floor.$count;
option routers 10.0.1$floor.254;
}
END
open(CONF, "+>/etc/dhcp3/dhcpd.conf");
foreach(@orig) {
$line = $_;
$line =~ s/  \# new entries here/$add\n  \# new entries here/;
print CONF $line;
}

close(CONF);
system("/etc/init.d/dhcp3-server restart");
close(IPS);
# add DNS records for this host
print "Adding DNS Entries ...\n";
open(REV, ">>/var/cache/bind/1$floor.0.10.in-addr.arpa");
print REV "$count\t\tPTR\t$firstname$secondname.zone.com.\n";
close(REV);
open(ZONE, ">>/var/cache/bind/zone.com");
print ZONE "$firstname$secondname\t28800\tIN\tA\t10.0.1$floor.$count\n";
close(ZONE);
system("rndc reload");
# Add two ipac rules, so we can see traffic going to/from this IP
print "Adding IP Accounting rules ...\n";
open(IPAC, ">>/etc/ipac-ng/rules.conf");
print IPAC <<END;
$firstname.$secondname in|ipac~i|+|all|0/0|10.0.1$floor.$count
$firstname.$secondname out|ipac~o|+|all|10.0.1$floor.$count|0/0
END
close(IPAC);

There are two programs for generating configuration files;

• HostDB
• netconfgen

This falls under the broader category of configuration management, which is addressed elsewhere on serverfault (eg here). I'd recommend puppet for this type of thing.

This approach is rather more indepth than the simple examples you were talking about, but it also allows for much more control of your systems