Lab 6.2 - Container Operations with Docker - alternatives
heiko_s
Posts: 99
Lab 6.2 is really nice - so many options to try out. But also so many syntax details to memorize.
A particularly mind-boggling example is this:sudo docker container inspect --format=’{{range.NetworkSettings.Networks}}{{.IPAddress}}{{end}}’ web-on-failure
Not a chance in the world I'll memorize that (I wonder who came up with this json syntax - must be a lonely fellow).
Turns out it's not so hard to parse the json file:sudo docker container inspect web-on-failure | grep \"IPAddress\": | cut -d '"' -f4 | uniq
And here a one-liner for the exercise:
[email protected]:~# curl $(sudo docker container inspect web-on-failure | grep \"IPAddress\": | cut -d '"' -f4 | uniq) Welcome to Container Fundamentals
The grep & cut works also with other parameters:
sudo docker container inspect web-on-failure | grep \"Gateway\": | cut -d '"' -f4 | uniq sudo docker container inspect web-on-failure | grep \"Runtime\": | cut -d '"' -f4 | uniq
Guess what's the runtime for the docker containers?
Unfortunately it fails when the value isn't quoted (""). For some incongruous reason many values are quoted, others are not. Example:
"Status": "running",
"Running": true,
"Paused": false,
"Restarting": false,
"OOMKilled": false,
Hope this is useful.
Comments
Hello @heiko_s,
Thank you for providing the grep/cut alternatives.
The JSON syntax assumes you are familiar with navigating the fields of the JSON file, while grep/cut requires you to know the position of the desired field. In both cases some some reconnaissance is required prior to extracting the desired value.
Regards,
-Chris
Thanks for the reply! Reconnaissance is definitely needed. But a simple grep gets me what I'm looking for, the rest is for scripting/automation.
Have been doing some other exercises using Podman and realised what was written in the lessons - no networking out of the box in unprivileged mode. The pod doesn't even get an IP. Looking forward to the container networking chapter.