Zabbix items: types, keys and intervals

You’ll install Nginx on web01 and create items that watch it from three angles: the agent (process count, page), the server (simple TCP check) and a calculated percentage. Commands run on web01 unless marked zbx01. web01 talks to zbx01 with PSK since Lesson 6, so zabbix_get commands include the PSK options; if you skipped Lesson 6, drop them.

1Install Nginx on web01

Run this on web01:

sudo apt install -y nginx
sudo ufw allow from 192.168.56.0/24 to any port 80 proto tcp
systemctl is-active nginx
curl -sI http://localhost/ | head -1

You should see this:

active
HTTP/1.1 200 OK

The ufw rule lets zbx01 reach the web server for the simple check later. Nginx starts a master process and one worker per CPU core by default, which is what the process count will show.

✅ Checkpoint: Nginx is active on web01 and returns HTTP 200 on localhost.

2Try the keys from the server first

Run this on zbx01 (put web01’s key in /tmp/web01.psk first, chmod 600):

P="--tls-connect psk --tls-psk-identity 'PSK web01' --tls-psk-file /tmp/web01.psk"
for k in 'proc.num[nginx]' 'net.tcp.service[http,,80]' 'vfs.fs.size[/,pused]' 'nginx.status'; do
  echo "== $k"; eval zabbix_get -s 192.168.56.81 -k "'$k'" $P
done

You should see this (the disk value is live and will differ):

== proc.num[nginx]
2
== net.tcp.service[http,,80]
1
== vfs.fs.size[/,pused]
48.534803
== nginx.status
ZBX_NOTSUPPORTED: Unsupported item key.

Testing keys with zabbix_get before creating items saves a lot of clicking. Two processes is one master and one worker: Ubuntu’s Nginx uses worker_processes auto, which starts one worker per CPU core, and web01 has 1 vCPU. nginx.status isn’t a real agent key, which you’ll use in Break It.

✅ Checkpoint: zabbix_get returns numbers for proc.num[nginx] and net.tcp.service, and “Unsupported item key.” for nginx.status.

3Create an agent item: Nginx processes

Open Data collection > Hosts, click Items next to web01, then Create item:

Click Add. Use the active type because web01 runs active checks (Lesson 4); a passive “Zabbix agent” item would also work here since web01 still accepts passive PSK connections. Tags let you filter Latest data and, later, route alerts.

✅ Checkpoint: The item “Nginx: number of processes” appears in web01’s item list as Enabled.

4Use Test before you save

Create a second item and, before saving, click Test at the bottom of the form:

In the Test dialog tick Get value from host and click Get value and test. Zabbix asks the agent through the server, using the host interface 192.168.56.81:10050 and its PSK settings, and shows the result. The Test button can only fetch a value for item types the server polls itself, so for “Zabbix agent (active)” items it can test preprocessing but can’t get a value from the host.

You should see the HTTP response headers followed by the Nginx welcome page HTML. Close the dialog and click Add.

✅ Checkpoint: Test returned an HTTP 200 response, and the “Nginx: home page” item is saved with type Text and 7d history.

5Add a simple check from the server side

A simple check is run by the server itself, so it tests the network path from zbx01 to web01 port 80, including web01’s firewall. It returns 1 when the TCP connection works and 0 when it doesn’t, which is not an error, just a value.

✅ Checkpoint: The simple check item is saved and, after a minute, Latest data shows 1.

6Add a calculated item

Calculated items do maths on other items. This one turns two template items into a percentage of memory used:

The key of a calculated item is just a unique name you choose. The formula uses the same function syntax as triggers: last(/host/key). Calculated items are evaluated by the server, so they don’t put any load on the agent.

✅ Checkpoint: “Memory used, %” shows a value in Latest data that, added to Available memory in %, makes 100.

7Watch the new items in Latest data

Open Monitoring > Latest data, filter host web01 and tag component: nginx, and click Apply.

Click History on the home page item to see the full text, and Graph on a numeric item to see its values over time. Text items have no graph, only a list of values.

✅ Checkpoint: All three Nginx items show recent values in Latest data.

8Use a flexible interval

Edit “Nginx: HTTP port reachable from Zabbix” and under Custom intervals add a Flexible row: interval 10s, period 1-5,09:00-18:00. Click Update. During weekday office hours the check now runs every 10 seconds, and every minute the rest of the time.

Note that Zabbix uses the server’s time zone for these periods.

✅ Checkpoint: The item shows “1m” with a custom interval, and during 09:00 to 18:00 on weekdays Last check updates every 10 seconds.