Docker: COPY failed: file not found in build context (Dockerfile) - docker

Question

I'd like to instruct Docker to COPY my certificates from the local /etc/ folder on my Ubuntu machine.
I get the error:
COPY failed: file not found in build context or excluded by
.dockerignore: stat etc/.auth_keys/fullchain.pem: file does not exist
I have not excluded in .dockerignore
How can I do it?
Dockerfile:
FROM nginx:1.21.3-alpine
RUN rm /etc/nginx/conf.d/default.conf
RUN mkdir /etc/nginx/ssl
COPY nginx.conf /etc/nginx/conf.d
COPY ./etc/.auth_keys/fullchain.pem /etc/nginx/ssl/
COPY ./etc/.auth_keys/privkey.pem /etc/nginx/ssl/
WORKDIR /usr/src/app
I have also tried without the dot --> same error
COPY /etc/.auth_keys/fullchain.pem /etc/nginx/ssl/
COPY /etc/.auth_keys/privkey.pem /etc/nginx/ssl/
By placing the folder .auth_keys next to the Dockerfile --> works, but not desireable
COPY /.auth_keys/fullchain.pem /etc/nginx/ssl/
COPY /.auth_keys/privkey.pem /etc/nginx/ssl/

Answer 1

The docker context is the directory the Dockerfile is located in. If you want to build an image that is one of the restrictions you have to face.
In this documentation you can see how contexts can be switched, but to keep it simple just consider the same directory to be the context. Note; this also doesn't work with symbolic links.
So your observation was correct and you need to place the files you need to copy in the same directory.
Alternatively, if you don't need to copy them but still have them available at runtime you could opt for a mount. I can imagine this not working in your case because you likely need the files at startup of the container.

Answer 2

#JustLudo's answer is correct, in this case. However, for those who have the correct files in the build directory and still seeing this issue; remove any trailing comments.
Coming from a C and javascript background, one may be forgiven for assuming that trailing comments are ignored (e.g. COPY my_file /etc/important/ # very important!), but they are not! The error message won't point this out, as of my version of docker (20.10.11).
For example, the above erroneous line will give an error:
COPY failed: file not found in build context or excluded by .dockerignore: stat etc/important/: file does not exist
... i.e. no mention that it is the trailing # important! that is tripping things up.

Answer 3

It's also important to note that, as mentioned into the docs:
If you use STDIN or specify a URL pointing to a plain text file, the system places the contents into a file called Dockerfile, and any -f, --file option is ignored. In this scenario, there is no context.
That is, if you're running build like this:
docker build -t dh/myimage - < Dockerfile_test
Any COPY or ADD, having no context, will throw the error mentioned or another similar:
failed to compute cache key: "xyz" not found: not found
If you face this error and you're piping your Dockerfile, then I advise to use -f to target a custom Dockerfile.
docker build -t dh/myimage -f Dockerfile_test .
(. set the context to the current directory)
Here is a test you can do yourself :
In an empty directory, create a Dockerfile_test file, with this content
FROM nginx:1.21.3-alpine
COPY test_file /my_test_file
Then create a dummy file:
touch test_file
Run build piping the test Dockerfile, see how it fails because it has no context:
docker build -t dh/myimage - < Dockerfile_test
[..]
failed to compute cache key: "/test_file" not found: not found
[..]
Now run build with -f, see how the same Dockerfile works because it has context:
docker build -t dh/myimage -f Dockerfile_test .
[..]
=> [2/2] COPY test_file /my_test_file
=> exporting to image
[..]

Answer 4

Check your docker-compos.yml, it might be changing the context directory.
I had a similar problem, with the only clarification: I was running Dockerfile with docker-compos.yml
This is what my Dockerfile looked like when I got the error:
FROM alpine:3.17.0
ARG DB_NAME \
DB_USER \
DB_PASS
RUN apk update && apk upgrade && apk add --no-cache \
php \
...
EXPOSE 9000
COPY ./conf/www.conf /etc/php/7.3/fpm/pool.d #<--- an error was here
COPY ./tools /var/www/ #<--- and here
ENTRYPOINT ["sh", "/var/www/start.sh"]
This is part of my docker-compose.yml where I described my service.
wordpress:
container_name: wordpress
build:
context: . #<--- the problem was here
dockerfile: requirements/wordpress/Dockerfile
args:
DB_NAME: ${DB_NAME}
DB_USER: ${DB_USER}
DB_PASS: ${DB_PASS}
ports:
- "9000:9000"
depends_on:
- mariadb
restart: unless-stopped
networks:
- inception
volumes:
- wp:/var/www/
My docker-compos.yml was changing the context directory. Then I wrote a new path in the Dockerfile and it all worked.
COPY ./requirements/wordpress/conf/www.conf /etc/php/7.3/fpm/pool.d
COPY ./requirements/wordpress/tools /var/www/
project structure

Answer 5

FWIW this same error shows up when running gcloud builds submit if the files are included in .gitignore

Answer 6

Have you tried doing a simlink with ln -s to the /etc/certs/ folder in the docker build directory?
Alternatively you could have one image that has the certificates and in your image you just COPY FROM the docker image having the certs.

Answer 7

I had the same error. I resolved it by adding this to my Docker build command:
docker build --no-cache -f ./example-folder/example-folder/Dockerfile
This repoints Docker to the home directory. Even if your Dockerfile seems to run (i.e. the system seems to locate it and starts running it), I found I needed to have the home directory pre-defined above, for any copying to happen.
Inside my Dockerfile, I had the file copying like this:
COPY ./example-folder/example-folder /home/example-folder/example-folder

Answer 8

I merely had quoted the source file while building a windows container, e.g.,
COPY "file with space.txt" c:/some_dir/new_name.txt
Docker doesn't like the quotes.