Zabbix can verify a huge number of things, among which is the current time on monitored systems. Let's create a quick configuration to do just that. We will create an item to collect the current time and then a trigger to compare that time with the current time on the Zabbix server. Of course, for this to work properly, the clock on the Zabbix server must be correct—otherwise, we would complain that it is wrong on all the other systems.
The first thing is the item to collect—the current time. Go to Configuration | Hosts, click on Items next to Another host, and then click on Create item. Fill in the following values:
- Name: Local time
- Key: system.localtime
- Units: unixtime
When you are done, click on the Add button at the bottom. This item returns the current time as a Unix timestamp. While a unit is not required for our trigger, we entered unixtime there. This will translate the timestamp to a human-readable value in the frontend. We discussed item units in more detail in Chapter 3, Monitoring with Zabbix Agents and Basic Protocols.
In the bar above the item list, click on Triggers, then click on the Create trigger button. Enter these values:
- Name: Incorrect clock on {HOST.NAME}.
- Expression: Click on Add and then on Select next to the Item field. In the item list for Another host, click on Local time in the Name column and click on Insert. The Expression field is filled with this expression: {Another host:system.localtime.last()}=0. This isn't actually what we need, but we tried to avoid the function drop-down here, so we will edit the expression manually. Change it to read this: {Another host:system.localtime.fuzzytime(30)}=0. (Another option is to use the drop-down, select the fuzzytime() function from the list, and add 30 for time.)
- Severity: Select the Warning option.
When you're done, click on the Add button at the bottom. The fuzzytime() function accepts a time period as a parameter. This makes it compare the timestamp of the item with the current time on the Zabbix server. If the difference is greater than the time specified in the parameter, it returns 0, which is the problem condition we wanted to catch. Again, if you are not sure about the return value of some trigger function, you'd better check the Zabbix manual. You can change your local time by using the timedatectl command.