Server preparation - Server monitoring

Automatic monitoring of production system is crucial for bussiness continuity. Monitoring is recommended also for the testing environment, but it is not mandatory. This page will show you how to set up basic monitoring of server with CzechIdM using Nagios NRPE. It is very useful to store monitored values for trend overview (e.g. with Munin). Some monitoring systems (like Zabbix) can store trends and monitor services at once. It is also practical to install iostat, vmstat and sar utilities on the server.

Example server parameters for this guide

Table with example monitoring parameters was created for these server resources.

• RHEL7-flavoured system.
• About 100GB HDD.
• At least 8GB RAM.
• At least 2x2GHz CPU.

When implementing server monitoring adjust monitored parameters for your particular deployment.

This is a list of monitored server's (and services') parameters. It should be treated as a bare minimum and, if needed, extended according to your company's policy. Parameters and their thresholds mentioned below are based on our best practices for the monitoring of a deployment.

We will use nrpe and probes from the standard system packages. We have epel repository enabled.

• NRPE daemon will listen on 5666\tcp (its default port). Open the port in your iptables by adding the rule: -A INPUT -m state –state ESTABLISHED,RELATED -p tcp –dport 5666 -j ACCEPT.
• All probes are located in their default installation location /usr/lib64/nagios/plugins/.
• We use one external probe check\_mem which can be downloaded here: https://exchange.nagios.org/directory/Plugins/System-Metrics/Memory/check_mem-2Esh/details. This probe, however, returns bad results on RHEL7 because of the different meaning of the free command output. You can dowload the fixed version from here.

Deployment

First, install necessary packages:

yum install nrpe nagios-plugins-nrpe nagios-plugins-swap nagios-plugins-disk nagios-plugins-load nagios-plugins-procs nagios-plugins-ntp nagios-plugins-http nagios-plugins-pgsql

If you use SELinux, we need to permit the check\_disk plugin access to the /sys/kernel/…. Easiest way (but not necessarily the most correct) is to set permissive mode for some plugins:

yum install policycoreutils-python
semanage permissive -a nagios_checkdisk_plugin_t

Edit the /etc/nagios/nrpe.cfg file and add your monitoring server address to the allowed\_hosts directive:

allowed_hosts=127.0.0.1,IPofMonitoringServer

Create a configuration of system checks in the file /etc/nrpe.d/checks.cfg. Fill in the YOUR\_NTP\_SERVER and IDM\_SERVICE\_DOMAIN\_NAME accordingly. The MONITORING\_USER and MONITORING\_USER\_PASSWORD are values filled with credentials of an user which is capable to log into the PostgreSQL database. Create separate user just for this purpose.

checks.cfg

command[check_swap]=/usr/lib64/nagios/plugins/check_swap -w 50% -c 10%
command[check_disk]=/usr/lib64/nagios/plugins/check_disk -w 90 -c 95
command[check_load]=/usr/lib64/nagios/plugins/check_load -w 4,3.5,3 -c 6,5.5,5
command[check_mem]=/usr/lib64/nagios/plugins/check_mem -w 90 -c 95
command[check_procs]=/usr/lib64/nagios/plugins/check_procs -w 300 -c 500
command[check_zombies]=/usr/lib64/nagios/plugins/check_procs -w 1 -c 5 -s Z
command[check_time]=/usr/lib64/nagios/plugins/check_ntp_time -H YOUR_NTP_SERVER -w60 -c300
command[check_idm]=/usr/lib64/nagios/plugins/check_http -H 127.0.0.1 -p 8080 -u '/idm/api/v1/status'
command[check_httpd]=/usr/lib64/nagios/plugins/check_http -H IDM_SERVICE_DOMAIN_NAME -S -p443 -w1
command[check_httpd_cert]=/usr/lib64/nagios/plugins/check_http -H IDM_SERVICE_DOMAIN_NAME -S -p443 -C30,7
command[check_postgres]=/usr/lib64/nagios/plugins/check_pgsql -H 127.0.0.1 -P 5432 -d template1 -l MONITORING_USER -p MONITORING_USER_PASSWORD -w0.5 -c1

Add the check\_mem script to the /usr/lib64/nagios/plugins/ directory, make it executable:

cp check_mem /usr/lib64/nagios/plugins/
chmod 755 /usr/lib64/nagios/plugins/check_mem

Create the MONITORING\_USER in the PostgreSQL. Generate some strong password - you can use pwgen for that.

create user monitoring password 'somepassword';

Start and enable the NRPE daemon:

systemctl start nrpe
systemctl enable nrpe

To test the probes, you can use check\_nrpe plugin:

/usr/lib64/nagios/plugins/check_nrpe -H 127.0.0.1 -b 127.0.0.1 -c check_swap

Nagios server configuration

This is a sample configuration for the Nagios server. It is meant more as an inspiration, feel free to adapt it to your Nagios deployment.

Configure the check\_nrpe command (you probably already have this in your Nagios configuration):

define command{
        command_name check_nrpe
        command_line /usr/lib64/nagios/plugins/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
}

Define CzechIdM server host:

define host {
        use                             linux-server
        host_name                       czechidm_server
        alias                           idmserver.example.com - CzechIdM server
        address                         1.2.3.4
        check_period                    24x7
        # we expect interval_length=60 as is the default, so 1440*60s = 1 day
        notification_interval           1440
        notification_period             24x7
}

Define checks:

define service {
        use                             generic-service
        host_name                       czechidm_server
        service_description             SWAP
        check_command                   check_nrpe!check_swap
        # we expect interval_length=60 as is the default, so 5*60s = 5 minutes
        check_interval 			5
        # we expect interval_length=60 as is the default, so 1440*60s = 1 day
        notification_interval           1440
        contacts 			user1,user2
        contact_groups			admins1,admins2
}

... and similarly the other checks ...