I have the tiniest of Docker Learn write-ups this week. 🙃

Alpine Builds and Runs so QUICKLY

Suppose you try each of the following commands:

1. docker run ubuntu
2. docker run fedora
3. docker run alpine
4. docker run golang

The first two commands install images and run super short-lived containers based on Ubuntu Linux and Fedora Linux, respectively. The third one does the same, but on Alpine Linux. By now I know that Alpine is 10x smaller than Ubuntu, but running these commands really brought the point home about why that makes a difference.

With the first two commands, it took a few seconds for the Docker daemon to download the images before it could run the container. But the third image (Alpine) downloaded so quickly that I almost didn't even notice the progress bar for it in the Docker terminal. The fourth command, on the other hand, took longer to execute than the first three combined.

docker images = docker image ls

If I run docker images or docker image ls, both commands will output the same thing:

$ docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
golang              latest              54e71dcafb7c        3 weeks ago         803MB
ubuntu              latest              775349758637        3 weeks ago         64.2MB
fedora              latest              f0858ad3febd        3 weeks ago         194MB
alpine              latest              965ea09ff2eb        4 weeks ago         5.55MB

This is a useful command, as I can now quickly compare the four images from above, by image size. The output seems to be sorted by image creation date rather than size. But it's still easy to compare the image sizes—and it's now obvious why the alpine image downloaded so quickly and the golang image so slowly, relatively speaking. Alpine was just 5.55 MB in size, compared to Golang's 803 MB.

By the way, docker images ls -a will also output the same information. (I don't yet know under what conditions this would not be the case)

And that's it! Until next week 👋🏾.