In this article we will install the Ganglia monitoring system on a set of machines running CentOS. There are two kinds of machines involved:

• The meta node: one machine that receives all measurements and presents it to a client through a website.
• The monitoring nodes: machines that run only the monitoring daemon and send the measurements to the meta node.

Meta node

For this example we assume the meta node has the IP address 192.168.1.253. We start by installing the necessary software:

rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-3.noarch.rpm
yum install rrdtool ganglia ganglia-gmetad ganglia-gmond ganglia-web httpd php apr apr-util

If you want to monitor the meta node as well as the monitoring nodes, edit the gmond configuration file /etc/gmond.conf:

cluster {
  name = "cluster1"
  owner = "owner1"
  latlong = "unspecified"
  url = "unspecified"
}

udp_send_channel {
  host = 192.168.1.253
  port = 8649
  ttl = 1
}

udp_recv_channel {
  port = 8649
}

Start the gmond service and make sure it starts at boot:

chkconfig gmond on
service gmond start

Edit the gmetad configuration file /etc/gmetad.conf:

data_source "my cluster" 192.168.1.253:8649

Start the gmetad service and make sure it starts at boot:

chkconfig gmetad on
service gmetad start

Enable the http daemon, to be able to see the pretty monitoring pictures:

chkconfig httpd on
service httpd start

Monitoring nodes

On all the monitoring nodes start by installing the necessary software:

rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-3.noarch.rpm
yum install ganglia-gmond

Edit the gmond configuration file /etc/gmond.conf. You can use an exact replica of the gmond configuration file shown for the meta node.
Start the gmond service and make sure it starts at boot:

chkconfig gmond on
service gmond start

If you would like to emit your own measurements (called metrics in Ganglia) and view them on the website, call the gmetric program:

gmetric --name mymetricname --value mymetricvalue --type string

To use the output of a program you wrote as a metric, simply call it like this, making sure to use backticks (`) instead of quotes (‘):

gmetric --name mymetricname --value `/home/user/mymetricprogram` --type string