Step 1: Build a list of hosts to monitor

For this I used an nmap ping test to generate a list of “up” hosts:

nmap -sP 10.0.0.0/24 -oG 10.0.0.0-255.255.255.0

This creates a list of IPs that are up in a format like this:


Host: 10.0.0.60 () Status: Up
Host: 10.0.0.61 () Status: Up
Host: 10.0.0.63 () Status: Up
Host: 10.0.0.64 () Status: Up
Host: 10.0.0.65 () Status: Up


Step 2: Parse out the IP address and run cfgmaker

Here’s the command I ran:

$ for i in `perl -ne 'chomp; next if $_ =~ /^#/; my @a = split(/ /); print "$a[1]\n";' 10.0.0.0-255.255.255.0`; do /usr/bin/cfgmaker --global 'LogFormat: rrdtool' --global 'WorkDir: /mrtg/data/mrtg' --global 'Options[_]: growright,bits' --global 'XSize[_]: 600' --global 'YSize[_]: 400' public@$i > /etc/mrtg/mrtg-$i ; done

This parses out the IP address from the input file and for each address, runs cfgmaker and puts the output in /etc/mrtg/mrtg-[ipaddress] .

Taking this a step further, I used gethostbyaddr to resolve the IPs to hostnames, so the MRTG files have the proper hostnames in them:

$ for i in `perl -MSocket -ne 'chomp; next if $_ =~ /^#/; my @a = split(/ /); my $ip = inet_aton($a[1]); my $host = gethostbyaddr($ip, AF_INET); print "$host\n";' 10.0.0.0-255.255.255.0`; do /usr/bin/cfgmaker --global 'LogFormat: rrdtool' --global 'WorkDir: /mrtg/data/mrtg' --global 'Options[_]: growright,bits' --global 'XSize[_]: 600' --global 'YSize[_]: 400' public@$i > /etc/mrtg/mrtg-$i ; done

Then all of the mrtg .cfg config files are in /etc/mrtg/, but who wants to put in all those cron entries to run each one? Not me. Simple fix?

cat /etc/mrtg/*.cfg > /etc/mrtg-all.cfg

Then you only have one cron entry.