Desarrollo Linux y software libre

In this article i will develop a plugin for mmonit for monitoring the CPU temperature and send alerts (emails) if it detects problems. Althought it seems to have a lot of steps, in 3 minutes you can get it up and running:

1º) Install the Linux package temperature.
After this, running «sensors» will show the temperature:

carlos@WhenIGrowUp:~$ sensors
k8temp-pci-00c3
Adapter: PCI adapter
Core0 Temp: -49.0°C
Core1 Temp: +56.0°C
M/B Temp: +55.0°C (low = -1.0°C, high = +127.0°C) sensor = thermistor
CPU Temp: +45.0°C (low = -1.0°C, high = +127.0°C) sensor = thermistor
Temp3: -128.0°C (low = -1.0°C, high = +127.0°C) sensor = disabled

2º) Download, check and install this script in your crontab.
This script will check the temperature, write it in the file /tmp/tempFile and, as Monit can’t read content of files, set the permissions as the following:

if temp is OK, /tmp/tempFile permissions will be 700
if it is a warning temp, /tmp/tempFile permissions will be 710
If it is a danger temp, /tmp/tempFile permissions will be 712

Later, Monit will check the permissions of this file, so it will know if the system is in trouble.

Run the script to test it:
carlos@shirley:~/hardware$ ./monit.temperature.sh
Temperature is: 45
Temp OK

Throubleshooting: if you get no result,
carlos@shirley:~/hardware$ ./monit.temperature.sh
Temperature is:
Temp OKedit the script and change CPU with the name of the line with the info (delete «temp3» and write «CPU» i.e) where you can see the temperature runnning «sensors»:
carlos@shirley:~/hardware$ nano monit.temperature.sh
temp=$(sensors | grep temp3) <-- Replace temp3 with CPU or a string of the output "sensors".

Now, install it in your crontab to be executed every minute:
# crontab -e
* * * * * /home/carlos/monit.temperature.sh


3º) Install and run Monit (not Mmonit, his commercial brother). Monit is GNU. Here you can see a quick guide.
Monit is an utility for monitoring systems (HD, processes, resources, connectivity, networks…), sending alerts and taking actions . Install it:

# sudo apt-get install monit
(or download last version here)


4º) Add these lines to /etc/monit/monitrc
# sudo nano /etc/monit/monitrc
[...]
check file TemperatureOK with path /tmp/tempFile
if failed permission 700 then alert
check file warningTemperature with path /tmp/tempFile
if failed permission 710 then alert
check file dangerTemperature with path /tmp/tempFile
if failed permission 712 then alert
[...]

for checking the correct syntax of Monit’s control file, run:
# sudo monit -tc /etc/monit/monitrc
Control file syntax OK

And restart it
# sudo /etc/init.d/monit restart

5º) Check Monit’s web interface, you will get something like this:
http://172.26.0.1:2812 (default: admin // monit)