Ganglia: Installation

This is part one of a three-part tutorial on installing and configuring Ganglia on Debian. The full tutorial includes

Installing Ganglia
Configuring Ganglia: the host node (gmetad)
Configuring Ganglia: the client nodes (gmon)

Supporting Packages

Ganglia uses RRDTool to generate and display its graphs and won't work without it. Fortunately, rrdtool doesn't need to be installed from source. Just run

apt-get install rrdtool librrds-perl librrd2-dev

In order to see the pie charts in PHP, you'll need an additional package:

apt-get install php5-gd

Getting Ganglia

Except for the frontend, Ganglia is in the Debian repository and easy to install. On the webserver, you'll need both packages, so

apt-get install ganglia-monitor gmetad

On all of the worker nodes (and head node, if it isn't running your webserver), you'll only need ganglia-monitor. You can apt-get this one at a time or see the Cluster Time-saving Tricks for tips on how to write a script.

Getting the Ganglia Frontend

Unfortunately, the frontend requires an entire build of Ganglia. That doesn't detract from the convenience of having the other two packages in the Debian repository, though, since you'll only need to build this one.
Visit Ganglia's SourceForge download page and copy the file location of the most recent version (the file should end in .tar.gz). Then, from whenever you keep your source files, run

wget http://downloads.sourceforge.net/ganglia/ganglia-3.0.7.tar.gz?modtime=1204128965&big_mirror=0

or similar. Then untar the file with

tar xvzf ganglia*.tar.gz

and cd into the new directory. Ganglia follows the typical source installation paradigm. Run ./configure --help to see all of the options. Important ones include

--prefix= - specify where the binaries should be installed, optional ones are often put in /opt
--enable-gexec - use gexec support
--with-gmetad - compile and install the metad daemon

The full line to enter should look similar to this:

./configure --prefix=/opt/ganglia --enable-gexec --with-gmetad

If it errors out and is unable to find rrd.h, make sure you installed everything listed above under "RRDTool". When it finishes successfully, you should see a screen like this:

Welcome to..
     ______                  ___
    / ____/___ _____  ____ _/ (_)___ _
   / / __/ __ `/ __ \/ __ `/ / / __ `/
  / /_/ / /_/ / / / / /_/ / / / /_/ /
  \____/\__,_/_/ /_/\__, /_/_/\__,_/
                   /____/

Copyright (c) 2005 University of California, Berkeley

Version: 3.0.7 (Fossett)
Library: Release 3.0.7 0:0:0

Type "make" to compile.

Go ahead and enter make, and after that finishes, make install.
Finally, when it's done, create a ganglia directory and copy all of /web to it:

mkdir /var/www/ganglia

cp web/* /var/www/ganglia

Apache

For convenience, you can update Apache to redirect any HTML requests for the root directory (ie, yourserver.yourdomain.com) to go straight to /ganglia. Open /etc/apache2/sites-enabled/000-default and find the block of code for the /var/www directory and add a redirect. The block should now look like this:

<Directory /var/www/>
                Options FollowSymLinks MultiViews
                AllowOverride None
                Order allow,deny
                allow from all
                RedirectMatch ^/$ /ganglia/
        </Directory>

After this, restart Apache:

apache2ctl restart

When you visit yourserver.yourdomain.com for the first time, you should be redirected to yourserver.yourdomain.com/ganglia, and you should have an "unspecified Grid report" as shown to the right. Cool!

Configuration Gmetad

/etc/gmetad.conf

The base of controls for gmetad in Debian is /etc/gmetad.conf. Going through the file from the beginning to the end, here are a few values to possibly change. You can search for these inside your favorite text editor.

Required Changes

Some of these are commented out by default (they have a # in front of the line). They need to be uncommented to work.

authority - This should be set to yourhost.yourdomain.com/ganglia. If you're behind a firewall and the URL appears as the firewall's, you should use that. For instance, my webserver is gyrfalcon, but through NAT with IPTables, my url appears as eyrie.mydomain.edu, and so I use that URL for authority.
trusted_hosts - If your webserver has multiple domain names, they should all be listed here. Otherwise, this can remain empty.

Optional Changes

gridname - If you don't like having the overall wrapper named "Grid", you can change it to something else.
rrd_rootdir - Ganglia needs to store a lot of data for RRD. If you want this stored some place other than /var/lib/ganglia/rrds, change this value.

Restarting Ganglia

After any changes, gmetad will need to be restarted. Do this with

/etc/init.d/gmetad restart

Configuring Gmon

The host running gmetad is probably also running gmon, if you want to monitor this host. It will need to be configured as a client node also.

/etc/gmond.conf

The file responsible for connecting each node appropriate to the server hosting Ganglia is /etc/gmond.conf. This file needs to be edited appropriately for each node. This can be done individually, or one file can be created on one node and it can be scripted and copied out to each one of the nodes.
The following values need to be edited:

name - This is the name of the cluster this node is associated with. This will show up on the web page.
owner - Different owners will be used to separate different clusters into administrative domains. If you only have one cluster, it's not such a big deal.
mcast_if - If the node has multiple interfaces, the one to be used to connect to the host should be specified.
num_nodes - The number of nodes in the cluster.

Restarting Ganglia Monitoring

After making the changes, gmond needs to be restarted on the node. Do this with

/etc/init.d/ganglia-monitor restart

Restarting Ganglia Host

After making the changes on all the nodes, gmetad on the webserver needs to be restarted. Do this with