Docker build colored messages unreadable

Question

I am using 'docker build' on Windows 10 to build asp net core web app image. However, since the last update, messages are colored in such a way that it gets unreadable. Searching on the internet did not provide any answers.
Any ideas on how to get around this?

Answer 1

[Updated 2022-08-02]

As of PR #2954 (which may take a bit to get released into Docker Desktop), you can run:

export NO_COLOR=1

There have also been changes to make the default text colors more readable.

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[Original answer]

With docker, you can pass the --help option to a command to see usage. E.g.:

$ docker build --help

Usage:  docker build [OPTIONS] PATH | URL | -

Build an image from a Dockerfile

Options:
      --add-host list           Add a custom host-to-IP mapping (host:ip)
      --build-arg list          Set build-time variables
      --cache-from strings      Images to consider as cache sources
      --disable-content-trust   Skip image verification (default true)
  -f, --file string             Name of the Dockerfile (Default is 'PATH/Dockerfile')
      --iidfile string          Write the image ID to the file
      --isolation string        Container isolation technology
      --label list              Set metadata for an image
      --network string          Set the networking mode for the RUN instructions during build (default "default")
      --no-cache                Do not use cache when building the image
  -o, --output stringArray      Output destination (format: type=local,dest=path)
      --platform string         Set platform if server is multi-platform capable
      --progress string         Set type of progress output (auto, plain, tty). Use plain to show container output (default "auto")
      --pull                    Always attempt to pull a newer version of the image
  -q, --quiet                   Suppress the build output and print image ID on success
      --secret stringArray      Secret file to expose to the build (only if BuildKit enabled): id=mysecret,src=/local/secret
      --squash                  Squash newly built layers into a single new layer
      --ssh stringArray         SSH agent socket or keys to expose to the build (only if BuildKit enabled) (format: default|<id>[=<socket>|<key>[,<key>]])                                                                                                                     
  -t, --tag list                Name and optionally a tag in the 'name:tag' format
      --target string           Set the target build stage to build.

For turning off the colored output, you can set --progress plain which removes the color formatted text and other tty features like updating the time for each build step. You can make this the default with:

export BUILDKIT_PROGRESS=plain

Alternatively, you may just want to change the color of your terminal. Black and white both work nicely. But a bluish background will clash with the blue text.

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The other option is to disable buildkit and revert back to the classic build engine. That can be done with an environment variable:

export DOCKER_BUILDKIT=0

or configuring the default in /etc/docker/daemon.json:

{
  "features": {"buildkit": false }
}

However, the classic builder will not support features being added to buildkit and is unlikely to see much development going forward.

Answer 2

Just add flag --progress plain while running docker build command, in the last.

for example,

docker build -t getting-started . --progress plain

Answer 3

Another ev option

export BUILDKIT_PROGRESS=plain