collectd on Debian
==================

General notes:
--------------

- Some plugins require additional libraries. To prevent you from having to
  install dependencies that you don't actually need those libraries are
  recommendations rather than dependencies. See README.Debian.plugins in the
  "collectd" package for details.

Configuring collectd:
---------------------

- See collectd.conf(5) for details about configuring collectd.

Access the collected data:
--------------------------

collectd is able to write data to CSV (comma separated list) and RRD (round
robin database - see http://oss.oetiker.ch/rrdtool/) files. However it does
not create graphs from these files. This package contains two sample scripts
in /usr/share/doc/collectd/examples/ which can be used for this purpose. They
are meant to be a starting point for your own experiments - more sophisticated
solutions are welcome.

- collectd2html.pl: This script by Vincent Stehlé will search for RRD files in
  "/var/lib/collectd/" and generate a static HTML file and a directory
  containing several PNG files which are graphs of the RRD files found.

- collection.cgi: Sample CGI script that creates graphs on the fly. The Perl
  modules "RRDs" (package librrds-perl), "URI:Escape" (package liburi-perl),
  "HTML::Entities" (package libhtml-parser-perl) and a CGI capable web server
  (e.g. apache2 or boa) are required for this script to run. Simply install
  the (gunzip'ed) script to a place where the webserver will treat it as a CGI
  script (/usr/lib/cgi-bin/ by default) and visit that page in a browser
  (http://localhost/cgi-bin/collection.cgi by default). Please refer to your
  webserver's documentation for more details.

  Starting with version 4, collection.cgi requires a small config file, which
  is installed to /etc/collectd/collection.conf. You should not need to change
  anything there.

Building your own plugins:
--------------------------

- Originally, plugins for collectd had to be written in C and linked as shared
  objects. Starting with version 4.0.0, it is also possible to use plugins
  written in the scripting language Perl or implemented as separate processes.
  See collectd-perl(5) and collectd-exec(5) for details.

- If you want to contribute plugins to the official distribution you should
  read http://collectd.org/dev-info.shtml.

- If you want to build C plugins for your personal use only simply install the
  collectd-dev package and use /usr/share/doc/collectd-dev/examples/myplugin.c
  as a starting point (Note: This is already a working example, though it does
  not collect any useful data).
  
  The resulting file can be compiled as follows:

    gcc -shared -fPIC -o myplugin.so myplugin.c

  Copy myplugin.so to /usr/lib/collectd and add the following line to your
  collectd config file:

    LoadPlugin myplugin

  Restart collectd and you're done.

- The collectd-dev package also provides an example Perl plugin that can be
  used as a starting point for your own development. It can be found in
  /usr/share/doc/collectd-dev/examples/MyPlugin.pm (Note: This is already a
  working example, though it does not collect any useful data).

  To enable the plugin, copy it to a place where Perl can find it (i.e. a
  subdirectory named "Collectd/Plugin" of a directory listed in @INC) and add
  the following line to the perl plugin section in your config file:

    LoadPlugin "Collectd::Plugin::MyPlugin"

  or

    BaseName "Collectd::Plugin"
    LoadPlugin MyPlugin

  Restart collectd and you're done.

Additional helper scripts:
--------------------------

- The directory /usr/share/doc/collectd/examples/PerlLib/ contains Perl
  modules which can be used in conjunction with collectd. See the perldoc
  documentation of the .pm-files to find out what they're good for.

- add_rra.sh: Before version 3.9.0 collectd used to create a different set of
  RRAs. The most detailed of these old RRAs had a one minute resolution. This
  script can be used to add three more RRAs: minimum, maximum and average with
  a ten second resolution and 2200 rows (~6 hours). This will make hourly
  statistics much more interesting. Please note that no sanity-checking
  whatsoever is performed. You can seriously screw up your RRD files if you
  don't know what you're doing.