All Agent data is pulled in one TCP connection during the unix-agent module. The module populates an $agent_data array which can be used by other modules. For example:

$agent_data = 
['app'] => 
['apache'] => 
... DATA ...
['bind'] =>
... DATA ...
['other'] =>
... DATA ...

Installation
The preferred method of running the Unix agent is via xinetd, preferably with an iptables firewall only allowing access from the monitoring server(s). Make sure this package is installed.

sudo apt-get install xinetd

Observium provides an example xinetd configuration file. Copy this from Observium to the server that will be running the agent.

scp /opt/observium/scripts/observium_agent_xinetd user@your_server:/etc/xinetd.d/observium_agent_xinetd

Edit observium_agent_xinetd so the Observium server is allowed to connect. You can do this by substituting 127.0.0.1, or place your IP after it, separated by a space. Make sure to restart xinetd afterwards so the configuration file is read.

sudo service xinetd restart

Copy the observium_agent script from Observium to the server that will be running the agent.

scp /opt/observium/scripts/observium_agent user@your_server:/usr/bin/observium_agent

Create a /usr/lib/observium_agent directory:

sudo mkdir -p /usr/lib/observium_agent

Next, create /usr/lib/observium_agent/scripts-available and /usr/lib/observium_agent/scripts-enabled directories.

Copy all agent scripts into the scripts-available directory, and place a symbolic link into scripts-enabled for the ones you want to enable:

scp /opt/observium/scripts/agent-local/* user@your_server:/usr/lib/observium_agent/scripts-available
sudo ln -s /usr/lib/observium_agent/scripts-available/os /usr/lib/observium_agent/scripts-enabled
sudo ln -s /usr/lib/observium_agent/scripts-available/dmi /usr/lib/observium_agent/scripts-enabled
sudo ln -s /usr/lib/observium_agent/scripts-available/apache /usr/lib/observium_agent/scripts-enabled

If you prefer to use a simpler layout and don’t need the ability to enable/disable specific scripts using symbolic links, you can alternatively simply create a /usr/lib/observium_agent/local directory and put the agent scripts you want to run in the local directory directly:

sudo mkdir -p /usr/lib/observium_agent/local

scp /opt/observium/scripts/agent-local/os user@your_server:/usr/lib/observium_agent/local

Enabling Observium’s Unix Agent module

Next, enable the unix-agent module (on your device’s settings tab, modules section) or globally for all *nix devices in the config.php configuration file:

$config['poller_modules']['unix-agent'] = 1;

Testing
To verify the agent is running, try to telnet from your Observium server to the monitored server on port 36602. If you see a blast of output, then the agent is working and is available to Observium.

telnet your_server 36602

To verify a specific script is working, you can run it from the command line on the monitored host. Make sure the script is executable (+x), otherwise the agent won’t run it.

chmod +x /usr/bin/observium_agent
/usr/bin/observium_agent

Modules
The scripts/agent-local directory of your Observium installation includes various modules which can be placed into /usr/lib/observium_agent/local to add additional functions to the agent. The files you want to be executed have to be marked as executable with chmod +x.

As this infrastructure is currently in development, it is recommended that these are downloaded to the server via SVN and symlinked into place, allowing updating of the scripts either manually or via cron.

Please refer to the Applications page for a list of supported apps.

Src: https://docs.observium.org/unix_agent/#enabling-observiums-unix-agent-module