labmasterkc/nettest repository overview

⁠labmaster-kc/nettest

⁠A simple docker image that uses curl, and a simple shell script to monitor external network information.

⁠Flow of operations:

• 1: Container starts up and sleeps number of seconds specified by NET_CHECK (Defaults to 900 seconds, or 15 minutes if variable not provided)
• 2: Once NET_CHECK time has passed, container waits between 1 and 15 seconds (Randomized each time the loop runs so that you can run multiple containers and not cause an API time-out)
  • Curl makes a call to https://api.ipify.org⁠ to determine current external IP address of host.
• 3: Container start-up and any external IP records are logged inside container to /tmp/nettest-log, this directory can be exported to make the logs available outside container

⁠Notes:

• Required variables have a default set of NULL, the container looks for these and exits with a message of problem in the log file. An easy way to trouble-shoot container is to map /tmp to an external directory (explained in the docker-compose and docker run example below)
• Only required ENV variables are DOMAIN and API_KEY, everything else has valid defaults
  • Labmaster 2020.11.05 - Added required ENV variable API_SECRET
• ENV variables "PUID" and "PGID" can be passed to set owner of logfile to a specific user, this is useful for mapping an external directory and setting the owner to a normal user

⁠Docker-compose example

• In this example I will be monitoring and updating cool-site.example.com, and checking for a change to DNS every 600 seconds (10 minutes)
  • volumes can be omitted or mapped somewhere such as a a folder under your home directory, simply change the left side to point to where you'd like to save DNS update logfiles
• Change "TIME_ZONE" to match your desired timezone. A vaild list can be found at https://www.wikiwand.com/en/List_of_tz_database_time_zones⁠ under the "TZ database name" column. Default is "America/New_York"

#docker-compose.yaml
version: "2.1"
services:
  nettest:
    image: labmasterkc/nettest
    container_name: nettest
    restart: unless-stopped
    environment:
      NET_CHECK: 600
      TIME_ZONE: America/New_York
    volumes:
      - /tmp:/tmp

⁠Support

• Shell access while the container is running:
  docker exec -it nettest /bin/bash
• To see log of DNS updates:
  docker exec -it nettest cat /tmp/*-log
• Container version number:
  docker inspect -f '{{ index .Config.Labels "build_version" }}' nettest
• Image version number:
  docker inspect -f '{{ index .Config.Labels "build_version" }}' labmasterkc/nettest