Give the name and… tag — Marcin Gładkowski

When a child birth one of the first thing is give a name! You should do the same with yours images! Why I writing about this? If you are not becarefule with images names and tags you can do the mess with our local docker images storage. Sometimes you have to prepare different images for some features/branches/deploys.

Let's prepare our dockerized website.

Website:

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>Title</title>

</head>
<body>
<h1>Hello World</h1>
</body>

Image to run container responsible for displaing it:

FROM nginx

COPY index.html /usr/share/nginx/html/index.html

OK, It's time to building. Build first version by command docker build . Then we want to something change in the our website and build again by build command. Which images we have?

Console output:

root@local:~/project$ docker images
REPOSITORY   TAG       IMAGE ID       CREATED              SIZE
<none>       <none>    c8af32463c20   5 seconds ago        141MB
<none>       <none>    f1663715c693   About a minute ago   141MB
nginx        latest    605c77e624dd   8 days ago           141MB

As you see there are a <none> words. It's not helpful when you want to pick up specific image. Why we have images without REPOSITORY and TAG? It's caused by build image without -t option These images were built by command docker build . How we can fix it or how we can build images? It's firstival we can tag image after build by command docker tag.

For example docker tag f1663715c693 website:1.0 and docker tag f1663715c693 website:1.2.

Console output:

root@local:~/project$ docker images
REPOSITORY   TAG       IMAGE ID       CREATED          SIZE
<none>       <none>    c8af32463c20   16 minutes ago   141MB
website      1.2       c8af32463c20   21 minutes ago   141MB
website      1.0       f1663715c693   22 minutes ago   141MB
nginx        latest    605c77e624dd   8 days ago       141MB

But this needs from us additional action.

Remember, we can do it while building an new image.

docker build -t website:1.3 .

Very interesting option is adding multiple specific tags at once. The case with latest is very helpful to tag a version of image and set it at latest.

docker build -t website:1.3 -t website:latest .

Full documentation about tagging we can find on docs.docker.com.

Symfony, where is your TDD?