check_netio is a simple and small monitoring plugin to retrieve statistics from network interfaces on Linux. Until now the plugin simply collected the data (Received Bytes and Transmitted Bytes) but never did a "real" check and simply returned OK. To simply gather data and graph them that was a quick and working method.
Today a new version (1.4) of check_netio is available. This version introduces a new optional parameter -e. With this parameter the plugin is told to check for interface errors. Let's try this:
$ /usr/lib/nagios/plugins/check_netio.sh -i enp5s0 -e
NETIO WARNING - Errors on enp5s0: 7 Receive errors, 0 Transmit errors|NET_enp5s0_RX=1995757695B;;;; NET_enp5s0_TX=4720483095B;;;; NET_enp5s0_ERR_IN=7;;;; NET_enp5s0_ERR_OUT=0;;;;
So far so good; the plugin detected 7 receive/rx errors on the interface.
Now the big question was what to do from now on? Should I set a threshold for the Receive/RX errors? I will go crazy doing this for 1000 servers whenever the error count increases... Instead I opted for a "short term memory" of the plugin itself. It will write the current error count into a temporary file and read this file out the next time it runs. By comparing the previous error count from the temporary file and the current error count, the plugin knows whether the error count increased and will again alert with a WARNING:
$ /usr/lib/nagios/plugins/check_netio.sh -i enp5s0 -e
NETIO WARNING - Errors on enp5s0: 14 Receive errors (previous check: 12), 2 Transmit errors (previous check: 0)|NET_enp5s0_RX=1995757695B;;;; NET_enp5s0_TX=4720483095B;;;; NET_enp5s0_ERR_RX=14;;;; NET_enp5s0_ERR_TX=2;;;;
If the error count did not increase, the plugin will return OK but with a hint that there were errors in the past:
$ /usr/lib/nagios/plugins/check_netio.sh -i enp5s0 -e
NETIO OK - enp5s0: Receive 1995757695 Bytes, Transmit 4720483095 Bytes - Hint: Previously detected errors (Receive: 14, Transmit: 2) but no change since last check|NET_enp5s0_RX=1995757695B;;;; NET_enp5s0_TX=4720483095B;;;; NET_enp5s0_ERR_RX=14;;;; NET_enp5s0_ERR_TX=2;;;;
On an interface with a steady increasing count of the errors, this will clearly be shown by the plugin.
Note: The performance data for the errors is always on, whether or not the -e parameter is used.
The documentation of check_netio is up to date now, too.
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