1. Get the Number of Logged-in Users#
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[root@web02 ~]#w
17:44:18 up 1:17, 2 users, load average: 0.01, 0.02, 0.05
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
root pts/0 11.0.1.1 16:31 11:46 0.07s 0.07s -bash
root pts/1 11.0.1.52 17:07 2.00s 0.04s 0.00s w
[root@web02 ~]#w|awk 'NR==1{print $4}'
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2. Define It as a Zabbix Monitoring Item#
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[root@web02 ~]# cat /etc/zabbix/zabbix_agentd.d/system.conf
UserParameter=login_number,w|awk 'NR==1{print $4}'
# zabbix_agentd -p can be used to check the item's syntax
[root@web02 ~]#zabbix_agentd -p|grep login_number
login_number [t|2]
# restart the agent
[root@web02 ~]# systemctl restart zabbix-agent.service
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3. Collect and Monitor from the Zabbix Server Side#
From the server, use the command line to test whether the custom value can be fetched through the monitoring item.
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# install the zabbix-get command
[root@zabbix ~]# yum -y install zabbix-get
[root@zabbix ~]#zabbix_get -s 172.16.1.8 -k login_number
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Add the monitoring item on the web page
View the monitoring item
4. Monitor Whether TCP Port 22 Is Alive#
Select the key value that matches the information you want to monitor.
Check whether the TCP port is in the LISTEN state. Returns 0 - not listening; 1 - listening.
Stop the sshd service on web02
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[root@web02 ~]# systemctl stop sshd
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Apply the value mapping
6. Custom Monitoring of Server Memory Percentage#
Step 1: Define a custom item to get the free-memory percentage
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[root@web02 ~]# cat /etc/zabbix/zabbix_agentd.d/system.conf
UserParameter=login_number,w|awk 'NR==1{print $4}'
UserParameter=mem_free,free|awk 'NR==2{print $NF/$2*100}'
[root@web02 ~]# systemctl restart zabbix-agent.service
[root@web02 ~]#zabbix_agentd -p|grep mem_free
mem_free [t|79.8753]
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Step 2: Test fetching the key value from the server and add the monitoring item
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[root@zabbix ~]#zabbix_get -s 172.16.1.8 -k mem_free
79.9775
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7. Set a Trigger for Available Memory#
Trigger an alert when the available-memory percentage drops below 20%.
Test: turn off the swap partition
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[root@web02 ~]# swapoff -a
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Use dd to stress-test and consume memory
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[root@web02 ~]# dd if=/dev/zero of=/dev/null bs=1200M count=2048
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Trigger an alert only when both conditions are met simultaneously.
Add the swap-free percentage
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[root@web02 ~]# cat /etc/zabbix/zabbix_agentd.d/system.conf
UserParameter=login_number,w|awk 'NR==1{print $4}'
UserParameter=mem_free,free|awk 'NR==2{print $NF/$2*100}'
UserParameter=swap_free,free -m|awk 'NR==3{print $3/$2*100}'
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Modify the trigger configuration
Then run the dd stress test again to check the result.