Linux Temperature logger

Linux system temperature logger compatible with Elastic.

This project allows a user to monitor the temperature of their Linux based system using Filebeat and Elasticsearch. A script reads the temperature of the CPU from the kernal and writes the output to a logfile in JSON format. Filebeat will then read that log file and ship the logs to Elasticsearch.

Tested Systems

This should work on most Linux systems however I've only tested on the following systems. If you are able to run cat /sys/class/thermal/thermal_zone0/temp and anything other than 0 is returned you should be good to go.

• - CentOS 7 - AMD64
• - CentOS 7 - Raspberry Pi4
• - Ubuntu 18.04 - AMD64
• - Ubuntu 18.04 - Raspberry Pi4
• - Ubuntu 20.04 - AMD64
• - Ubuntu 20.04 - Raspberry Pi4

How it works

1. A Bash script runs in the background to collect the system temperature at a given interval and then writes it to a log file.
2. Filebeat reads the log file line by line and ships it to Elasticsearch.
3. Elasticsearch indexes the documents.

The temperature script writes logs as JSON structured entries, Filebeat then processes the JSON to extract key/value pairs, this mitigates the need for any further log processing i.e., Ingest Pipelines or Logstash.

Unfortunately, Elastic Common Schema is yet to have a field mapping for system temperature (or any temperature at that), therefore a field is needed to be added to hold the system temp. To avoid adding any custom index templates the script formats the temperature logs in such a way that Elasticsearch will dynamically map the custom temperature field to a float. This allows mathematical operations and visualisations to be carried on the field contents such as line charts.

By running the script as a service, it allows for easy management as it will automatically start with the system.

Manual Install

1. Create script directory. sudo mkdir /opt/temperature-logger/
2. Copy the script. sudo cp ./temp-logger.sh /opt/temperature-logger/temp-logger.sh
3. Copy the service. sudo cp ./temp-logger.service /etc/systemd/system/temp-logger.sh
4. Install Filebeat - https://www.elastic.co/guide/en/beats/filebeat/current/setup-repositories.html
5. Configure Filebeat. I have included a very basic Filebeat config in the resources folder. The input section is needed.
6. Enable temp_logger service systemctl enable temp-logger.service
7. Start temp_logger service systemctl start temp-logger.service

Install using Ansible

If you use ansible there is a playbook pre-created in the ansible directory which will install the temperature logger with default variables.

1. cd in to the ansible directory.
2. Update ansible.cfg to point to your inventory or add hosts to the hosts file.
3. Run playbook ansible-playbook temp-logger.yml

You will need to manually install Filebeat or use a premade ansible playbook. An example config for Filebeat is included in the resources directory. The input section should be used even if using own base config!

Ansible Variables

Variable	Description
service_name	Name of the service to be installed. Default=temp-logger
script_file_path	The local path to the logger script. Default=../temp-logger.sh
service_file_path	The local path to the service file. Default=../temp-logger.service
script_dest	Path of where to install the logging script. Default=/opt/temperature-logger/

Script Variables

These variables reside in the temp-logger.sh script and control the behaviour of the script.

Variable	Description
PROBE_RATE	Rate of which the temperature is recorded
RETENTION_PERIOD	How many days to retain log files for. Default=30
TEMPERATURE_LOG_PATH	Path of where to store log files. Default=/var/log/temperature/
TEMPERATURE_LOG_FILE_NAME	Log file name. Default=cpu_temp