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11 External checks


External check is a check executed by Zabbix server by running a shell script or a binary. However, when hosts are monitored by a Zabbix proxy, the external checks are executed by the proxy.

External checks do not require any agent running on a host being monitored.

The syntax of the item key is:



script Name of a shell script or a binary.
parameter(s) Optional command line parameters.

If you don't want to pass any parameters to the script you may use:

script[] or

Zabbix server will look in the directory defined as the location for external scripts (parameter 'ExternalScripts' in Zabbix server configuration file) and execute the command. The command will be executed as the user Zabbix server runs as, so any access permissions or environment variables should be handled in a wrapper script, if necessary, and permissions on the command should allow that user to execute it. Only commands in the specified directory are available for execution.

Do not overuse external checks! As each script requires starting a fork process by Zabbix server, running many scripts can decrease Zabbix performance a lot.

Usage example

Executing the script with the first parameters '-h'. The second parameter will be replaced by IP address or DNS name, depending on the selection in the host properties.["-h","{HOST.CONN}"]

Assuming host is configured to use IP address, Zabbix will execute: '-h' ''

External check result

The return value of an external check is a standard output together with a standard error produced by the check.

An item that returns text (character, log, or text type of information) will not become unsupported in case of a standard error output.

The return value is limited to 16MB (including trailing whitespace that is truncated); database limits also apply.

If the requested script is not found or Zabbix server has no permissions to execute it, the item will become unsupported and a corresponding error message will be displayed.

In case of a timeout, the item will become unsupported, a corresponding error message will be displayed, and the process forked for the script will be terminated.