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Sometimes you may want to run an agent check that does not come predefined with Zabbix. This is where user parameters come to help.
You may write a command that retrieves the data you need and include it in the user parameter in the agent configuration file ('UserParameter' configuration parameter).
A user parameter has the following syntax:
UserParameter=<key>,<command>
As you can see, a user parameter also contains a key. The key will be necessary when configuring an item. Enter a key of your choice that will be easy to reference (it must be unique within a host). Restart the agent.
Then, when configuring an item, enter the key to reference the command from the user parameter you want executed.
User parameters are commands executed by Zabbix agent. Up to 512KB of data can be returned. /bin/sh is used as a command line interpreter under UNIX operating systems. This way you can enhance the functionality of Zabbix agents.
See a step-by-step tutorial on making use of user parameters.
A simple command:
UserParameter=ping,echo 1
The agent will always return '1' for an item with 'ping' key.
A more complex example:
UserParameter=mysql.ping,mysqladmin -uroot ping|grep -c alive
The agent will return '1', if MySQL server is alive, '0' - otherwise.
Flexible user parameters accept parameters with the key. This way a flexible user parameter can be the basis for creating several items.
Flexible user parameters have the following syntax:
UserParameter=key[*],command
Parameter | Description |
---|---|
Key | Unique item key. The [*] defines that this key accepts parameters within the brackets. Parameters are given when configuring the item. |
Command | Command to be executed to evaluate value of the key. Use positional references $1…$9 to refer to the respective parameter in the item key. Zabbix parses the parameters enclosed in [ ] of the item key and substitutes $1,…,$9 in the command accordingly. $0 will be substituted by the original command (prior to expansion of $0,…,$9) to be run. |
$$2
will actually turn into $2
when executing the command.Something very simple:
UserParameter=ping[*],echo $1
We may define unlimited number of items for monitoring all having format ping[something].
Let's add more sense!
UserParameter=mysql.ping[*],mysqladmin -u$1 -p$2 ping | grep -c alive
This parameter can be used for monitoring availability of MySQL database. We can pass user name and password:
mysql.ping[zabbix,our_password]
How many lines matching a regular expression in a file?
UserParameter=wc[*],grep -c "$2" $1
This parameter can be used to calculate number of lines in a file.
wc[/etc/passwd,root] wc[/etc/services,zabbix]