Can you make any sense of Dockers error-messages?

Question

I admit, I am a newbie in the container-world. But I managed to get docker running on my W10 with WSL2. I can also use the docker-UI and run Containers/Apps or Images. So I believe that the infrastructure is in place and uptodate. Yet, when I try even the simplest Dockerfile, it doesn't seem to work and I don't understand the error-messages it gives: This is Dockerfile:

FROM ubuntu:20.04

(yes, a humble beginning - or an extremly slimmed down repro)

docker build Dockerfile
[+] Building 0.0s (2/2) FINISHED
 => ERROR [internal] load build definition from Dockerfile                                                                                                                    0.0s
 => => transferring dockerfile: 33B                                                                                                                                           0.0s
 => ERROR [internal] load .dockerignore                                                                                                                                       0.0s
 => => transferring context: 33B                                                                                                                                              0.0s
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 > [internal] load build definition from Dockerfile:
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 > [internal] load .dockerignore:
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failed to solve with frontend dockerfile.v0: failed to build LLB: error from sender: Dockerfile is not a directory

Answer 1

You need to run docker build -f [docker_file_name] . (don't miss the dot at the end).

If the name of your file is Dockerfile then you don't need the -f and the filename.

Answer 2

I faced a similar issue, I use the docker desktop for windows. Restarted the laptop and the issue was resolved. Hope it may help someone.

Answer 3

For me, I had a Linux symlink in the same directory as the Dockerfile. When running docker build from Windows 10, it gave me the ERROR [internal] load build definition from Dockerfile. I suspect Docker docker build . scans the directory and, if it can't read one file, it crashes. For me, I mounted the directory with WSL and removed the symblink.