# 3 Agent

#### Overview

Zabbix agent is deployed on a monitoring target to actively monitor
local resources and applications (hard drives, memory, processor
statistics etc).

The agent gathers operational information locally and reports data to
Zabbix server for further processing. In case of failures (such as a
hard disk running full or a crashed service process), Zabbix server can
actively alert the administrators of the particular machine that
reported the failure.

Zabbix agents are extremely efficient because of use of native system
calls for gathering statistical information.

##### Passive and active checks

Zabbix agents can perform passive and active checks.

In a [passive
check](/manual/appendix/items/activepassive#passive_checks) the agent
responds to a data request. Zabbix server (or proxy) asks for data, for
example, CPU load, and Zabbix agent sends back the result.

[Active checks](/manual/appendix/items/activepassive#active_checks)
require more complex processing. The agent must first retrieve a list of
items from Zabbix server for independent processing. Then it will
periodically send new values to the server.

Whether to perform passive or active checks is configured by selecting
the respective monitoring [item
type](/manual/config/items/itemtypes/zabbix_agent). Zabbix agent
processes items of type 'Zabbix agent' or 'Zabbix agent (active)'.

#### Supported platforms

Zabbix agent is supported for:

-   Linux
-   IBM AIX
-   FreeBSD
-   NetBSD
-   OpenBSD
-   HP-UX
-   Mac OS X
-   Solaris: 8, 9, 10, 11
-   Windows: all desktop and server versions since 2000

##### Installation

See [installation
instructions](/manual/installation/install#installing_zabbix_daemons)
for Zabbix agent.

::: noteimportant
In general, 32bit Zabbix agents will work on 64bit
systems, but may fail in some cases.
:::

#### Running agent processes

Zabbix agent is run on the host being monitored.

Zabbix agent on UNIX runs as a daemon process. To start the agent
(standalone daemon), execute:

    shell> cd sbin
    shell> ./zabbix_agentd

Zabbix agent on Windows runs as a Windows service. You can run a single
instance of Zabbix agent or multiple instances of the agent on a host. A
single instance can use the default configuration file or a
configuration file specified in the command line. In case of multiple
instances each agent instance must have its own configuration file (one
of the instances can use the default configuration file).

The following command line parameters can be used with Zabbix agent:

|**Parameter**|**Description**|
|-------------|---------------|
|**UNIX and Windows agent**|<|
|-c --config <config-file>|Absolute path to the configuration file.<br>You may use this option to specify a configuration file that is not the default one.<br>On UNIX, default is /usr/local/etc/zabbix\_agentd.conf or as set by [compile-time](/manual/installation/install#installing_zabbix_daemons) variables *--sysconfdir* or *--prefix*<br>On Windows, default is c:\\zabbix\_agentd.conf|
|-p --print|Print known items and exit.<br>*Note*: To return [user parameter](/manual/config/items/userparameters) results as well, you must specify the configuration file (if it is not in the default location).|
|-t --test <item key>|Test specified item and exit.<br>*Note*: To return [user parameter](/manual/config/items/userparameters) results as well, you must specify the configuration file (if it is not in the default location).|
|-h --help|Display help information|
|-V --version|Display version number|
|**Windows agent only**|<|
|-m --multiple-agents|Use multiple agent instances (with -i,-d,-s,-x functions).<br>To distinguish service names of instances, each service name will include the Hostname value from the specified configuration file.|
|**Windows agent only (functions)**|<|
|-i --install|Install Zabbix Windows agent as service|
|-d --uninstall|Uninstall Zabbix Windows agent service|
|-s --start|Start Zabbix Windows agent service|
|-x --stop|Stop Zabbix Windows agent service|

See [more
details](/manual/appendix/install/windows_agent#installing_agent_as_windows_service)
on installing and running Zabbix agent on Windows.

Specific **examples** of using command line parameters:

-   printing all built-in agent items with values
-   testing a user parameter with "mysql.ping" key defined in the
    specified configuration file
-   installing a "Zabbix Agent" service for Windows using the default
    path to configuration file c:\\zabbix\_agentd.conf
-   installing a "Zabbix Agent \[Hostname\]" service for Windows using
    the configuration file zabbix\_agentd.conf located in the same
    folder as agent executable and make the service name unique by
    extending it by Hostname value from the config file

```{=html}
<!-- -->
```
    shell> zabbix_agentd --print
    shell> zabbix_agentd -t "mysql.ping" -c /etc/zabbix/zabbix_agentd.conf
    shell> zabbix_agentd.exe -i
    shell> zabbix_agentd.exe -i -m -c zabbix_agentd.conf

##### Process user

Zabbix agent on UNIX is designed to run as a non-root user. It will run
as whatever non-root user it is started as. So you can run agent as any
non-root user without any issues.

If you will try to run it as 'root', it will switch to a hardcoded
'zabbix' user, which must be present on your system. You can only run
agent as 'root' if you modify the 'AllowRoot' parameter in the agent
configuration file accordingly.

#### Locale

Note that the agent requires a UTF-8 locale so that some textual agent
items can return the expected content. Most modern Unix-like systems
have a UTF-8 locale as default, however, there are some systems where
that may need to be set specifically.

##### Configuration file

For details on configuring Zabbix agent see the configuration file
options for [zabbix\_agentd](/manual/appendix/config/zabbix_agentd) or
[Windows agent](/manual/appendix/config/zabbix_agentd_win).