How to see all output when executing `docker build`

Question

The docker build is scrolling the output.

docker build -t "setuppython"  .

In the screenshot the area enclosed in the red rectangle is being scrolled - and the prior output is lost. I would like to be able to see all output without it being hidden:

Here is the Dockerfile

from ubuntu:20.04
WORKDIR .
RUN echo "HOME is $HOME"
COPY  ./setup-python.sh .

RUN ./setup-python.sh

How can that be done?

Answer 1

Set the --progress=plain option, so modify the build command as follows:

docker build -t "setuppython" --progress=plain .

Alternatively, you can set the BUILDKIT_PROGRESS environment variable (documented here) instead of explicitly setting this option for each individual build command, like so:

export BUILDKIT_PROGRESS=plain

The --progress argument and/or the BUILDKIT_PROGRESS environment variable accept the values auto, plain, and tty. Using tty, the output will try to be "nicer" for interactive terminals (so it overwrites itself), and plain will simply output everything. The auto setting (default) will try to determine which of the two is more appropriate for the current environment.