====== collectd ======

Collectd collects data from your system (CPU, load, etc) and the software it's running (e.g. Apache, MySQL).





===== Installation =====

Just follow the instructions on the [[http://collectd.org/wiki/index.php/First_steps|collectd wiki]]. The wiki assumes you're using a Debian-based system, but they're advising you to compile from source code anyway. I got collectd to work on my Debian-based systems by simply using apt-get:

<code>
apt-get install collectd
</code>

You may also need to install libcurl (used by collectd's Apache plugin):

<code>
apt-get install curl
</code>

Collectd's core task is to collect data, but they also provide a simple graphics generator, based on perl scripts. Here's what you've got to install to get it working:

<code>
apt-get install librrds-perl libconfig-general-perl libhtml-parser-perl  libregexp-common-perl
</code>


==== Compiling collectd ====

Make sure your system meets all the requirements. Each collectd plugin may also have its own requirements. See the [[http://git.verplant.org/?p=collectd.git;a=blob;hb=master;f=README|README]].

On my Ubuntu 6 system, I also had to install ''libcurl3-dev''. To make sure that your system meets the requirements, use the --enable switch:

<code>
./configure --enable-apache --enable-mysql
</code>

===== Configuration =====

Now it's time to configure collectd. Use a text editor (e.g. nano) to edit ''/etc/collectd.conf''. An important thing to get right immediately, is the ''Interval'' directive. If you change this setting afterward, you apparently have to completely reinstall collectd or remove all its data files. The default, 10 seconds, is okay.




==== Apache Plugin ====

To use the Apache plugin, you have to configure Apache first: collectd uses mod_status. Debian-based systems usually have mod_status installed already. All you have to do, is tell Apache you want to use it. Edit the ''/etc/apache2/apache2.conf'' file by adding:

<code>
ExtendedStatus on
<Location /mod_status>
  SetHandler server-status
</Location>
</code>

Don't forget to restart Apache after saving the ''apache2.conf'' file.

Now you've got to uncomment the load directive for the plugin in the ''/etc/collectd.conf'' file:

<code>
LoadPlugin apache
</code>

And add some configuration for the Apache plugin in the ''/etc/collectd.conf'' file:

<code>
<Plugin apache>
        URL "http://localhost/mod_status?auto"
#       User "www-user"
#       Password "secret"
#       VerifyPeer false
#       VerifyHost false
#       CACert "/etc/ssl/ca.crt"
</Plugin>
</code>

Please be warned that your Apache server info, as printed by http://localhost/mod_status, will be accessible by whatever name your localhost has to the outside world. E.g., if your system is called mymachine.com, then Apache will happily ouput its status through mymachine.com/mod_status.





==== MySQL Plugin ====

Just create a MySQL user called collectd, with no privileges at all. Restrict this user to the localhost and make up a good, strong password.

Again, uncomment the load directive in the ''/etc/collectd.conf'' file:

<code>
LoadPlugin mysql
</code>

And configure the plugin:

<code>
<Plugin mysql>
        Host "localhost"
        User "collectd"
        Password "secret_password"
#       Database "db_name"
</Plugin>
</code>

Now (re)start the daemon: ''/etc/init.d/collectd restart'', or: ''/opt/collectd/sbin/collectd''.






==== Creating Graphs ====

Copy the directory ''/usr/share/doc/collectd/examples/collection3'' to a place where your cgi scripts are running, e.g. ''/home/onno/cgi-bin''. Change the ownership of the ''collection3'' directory:

<code>
chown -R www-data:www-data collection3
</code>

You can now access your graphs at ''http://yoursite.com/cgi-bin/collection3/bin/index.cgi''.

Please note that the graphing scripts seem to require at least Perl 5.10. Ubuntu 6.06 carries Perl 5.8.7.


=== Visage ===

Visage is a Ruby / Sinatra based tool which uses collectd's rrdtool plugin to plot data in graphs.

The [[http://github.com/auxesis/visage|Visage GitHub site]] explains the installation and configuration. If you run into trouble with Sinatra, check [[http://blog.yetisoftware.com/2009/03/07/sinatra-on-dreamhost/|this blog]].


===== Running and Securing Collectd =====

To run collectd, simply use: ''/etc/init.d/collectd restart'', or ''/opt/collectd/sbin/collectd''. If you've installed collectd through apt-get, it's going to start automatically on reboot.

You can secure access to the graphs by simply securing the directory through Apache: [[linux:apache_webserver#securing_a_web_directory_with_apache]].