This posting is ~4 years years old. You should keep this in mind. IT is a short living business. This information might be outdated.
While searching for a simple monitoring für my root servers, I’m stumbled over a python-based software called Simplemonitor. Other alternatives, like Nagios, or forks like Incinga etc., were a bit too much for my needs.
What is SimpleMonitor?
SimpleMonitor is a Python script which monitors hosts and network connectivity. It is designed to be quick and easy to set up and lacks complex features that can make things like Nagios, OpenNMS and Zenoss overkill for a small business or home network. Remote monitor instances can send their results back to a central location.
My requirements were simple:
Disk space monitoring
Monitoring is nothing without alerting, so I was pretty happy that Simplemonitor is able to send messages into a Slack channel! But it can also send e-mails, SMS, or it can write into a log file. To get a full feature overview, visit the Simplemonitor website.
The project is hosted on GitHub. If you are familiar with Python, you can contribute to the project, or you can add features as you need.
Installation & configuration
The installation is pretty simple: Just fetch the ZIP or the tarball from the project website, and extract it.
The configuration is split into two files:
The naming is a bit confusing. The monitor.ini contains the basic monitoring configuration, like the interval for the checks, the alerting and reporting settings. The monitors.ini contains the configuration of the service checks. That’s confusing, that confused me, and so I changed the name of the monitors.ini to services.ini.
The services.ini (monitors.ini) contains the service checks. This is a short example of a ping, a service check, a port check, and a disk space check.
In case of a service fail, or service recovery, a notification is sent to the configured Slack channel.
To start Simplemonitor, just start the monitor.py. It expects the monitor.ini in the same directory.
[email protected] /opt/simplemonitor # python2 monitor.py -v
--> Loading main config from monitor.ini
--> Loading monitor config from services.ini
Adding host monitor ping-host2
Adding rc monitor svc-postfix-host1
Adding rc monitor svc-nginx-host1
Adding rc monitor svc-mysql-host1
Adding rc monitor svc-fail2ban-host1
Adding rc monitor svc-postgrey-host1
Adding rc monitor svc-phpfpm-host1
Adding rc monitor svc-named-host1
Adding diskspace monitor diskspace
--> Loaded 9 monitors.
Adding logfile logger logfile
Adding slack alerter slack
--> Starting... (loop runs every 60s) Hit ^C to stop
php_fpm is running as pid 33937.
named is running as pid 566.
fail2ban is running as pid 41306.
postgrey is running as pid 649.
mysql is running as pid 23726.
postfix is running as pid 53332.
nginx is running as pid 52736.
I really like the simplicity of Simplemonitor. Download, extract, configure, run, done. That’s what I’ve searched for. It is still under development, but you should not expect that it will gain much complexity. Even if features will be added, it should be a simple monitoring.
This posting is ~5 years years old. You should keep this in mind. IT is a short living business. This information might be outdated.
The Simple Network Management Protocol (SNMP) is a protocol for monitoring and configuration of network-attached devices. SNMP exposes data in the form of variables and values. These variables can then be queried or set. A query retrieves the value of a variable, a set operation assigns a value to a variable. The variables are organized in a hierarchy and each variable is identified by an object identifiers (OID). The management information base (MIB ) describes this hierarchy. MIB files (simple text files) contain metadata for each OID. These are necessary for the translation of a numeric OID into a human-readable format. SNMP knows two devices types:
the managed device which runs the SNMP agent
the network management station (NMS) which runs the management software
The NMS queries the SNMP agent with GET requests. Configuration changes are made using SET requests. The SNMP agent can inform the NMS about state changes using a SNMP trap message. The easiest way for authentication is the SNMP community string.
SNMP is pretty handy and it’s still used, especially for monitoring and managing networking components. SNMP has the benefit, that it’s very lightweight. Monitoring a system with WBEM or using an API can cause slightly more load, compared to SNMP. Furthermore, SNMP is a internet-protocol standard. Nearly every device supports SNMP.
Monitoring host hardware with SNMP
Why should I monitor my ESXi host hardware with SNMP? The vCenter Server can trigger an alarm and most customers use applications like VMware vRealize Operations, Microsoft System Center Operations Manager, or HPE Systems Insight Manager (SIM). There are better ways to monitor the overall health of an ESXi host. But sometimes you want to get some stats about the network interfaces (throughput), or you have a script that should do something, if a NIC goes down or something else happens. Again, SNMP is very resource-friendly and widely supported.
Configure SNMP on ESXi
I focus on ESXi 5.1 and beyond. The ESXi host is called “the SNMP Agent”. We don’t configure traps or trap destinations. We just want to poll the SNMP agent using SNMP GET requests. The configuration is done using esxcli . First of all, we need to set a community string and enable SNMP.
[[email protected]:~] esxcli system snmp set -c public -e true
[[email protected]:~] esxcli system snmp get
That’s it! The necessary firewall ports and services are opened and started automatically.
Querying the SNMP agent
I use a CentOS VM to show you some queries. The Net-SNMP package contains the tools snmpwalk and snmpget. To install the Net-SNMP utils, simply use yum .
ifOperStatus.1 corresponds with ifDescr.1 , ifOperStatus.2 corresponds with ifDescr.2 and so on. The ifOperStatus corresponds with the status of the NICs in the vSphere Web Client.
If you want to monitor the fans or power supplies, use these these OIDs.
HOST-RESOURCES-MIB::hrDeviceDescr.35 = STRING: POWER Power Supply 1
HOST-RESOURCES-MIB::hrDeviceDescr.36 = STRING: POWER Power Supply 2
HOST-RESOURCES-MIB::hrDeviceDescr.37 = STRING: FAN Fan Block 1
HOST-RESOURCES-MIB::hrDeviceDescr.38 = STRING: FAN Fan Block 2
HOST-RESOURCES-MIB::hrDeviceDescr.39 = STRING: FAN Fan Block 3
HOST-RESOURCES-MIB::hrDeviceDescr.40 = STRING: FAN Fan Block 4
HOST-RESOURCES-MIB::hrDeviceStatus.35 = INTEGER: running(2)
HOST-RESOURCES-MIB::hrDeviceStatus.36 = INTEGER: running(2)
HOST-RESOURCES-MIB::hrDeviceStatus.37 = INTEGER: running(2)
HOST-RESOURCES-MIB::hrDeviceStatus.38 = INTEGER: running(2)
HOST-RESOURCES-MIB::hrDeviceStatus.39 = INTEGER: running(2)
HOST-RESOURCES-MIB::hrDeviceStatus.40 = INTEGER: running(2)
SNMP offers a simple and lightweight way to monitor a managed device. It’s not a replacement for vCenter, vROps or SCOM. But it can be an addition, especially because SNMP is an internet-protocol standard.
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