.dockerignore not being read on image build

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I've been stuck on this for awhile. I would like docker to ignore a particular directory when building an image, because my user account does not have permissions to read that directory. I cannot move it, so that's not an alternative.

This is the structure of my project. docker/data is the directory that I do not have permissions to read, and docker/node-express.dockerfile is the image I'm trying to build.

enter image description here

Running docker build --no-cache --tag node-express --file ./docker/node-express.dockerfile . in the root directory outputs the error

error checking context: 'can't stat '/home/anthony/Repositories/Anthony-Monterrosa/aws-postgres-node-stack/docker/data''.

After this error and a bit of googling I learned about .dockerignore files, and made one in the root directory. The following is the file's text.

docker/data

I ran the command again but got an identical error. A bit more googling and I found out about image-specific .dockerignore files, so I set DOCKER_BUILDKIT to 1, created docker/node-express.dockerfile.dockerignore with the following content

data
docker/data

(I am not sure how relative paths work with image-specific .dockerignores, so I added both). Ran the command again, but still with the same error.

So, I don't seem to have ignores working correctly with either .dockerignore file, or both. What am I missing here?

docker-compose docker
1 Answers

The error is:

error checking context: 'can't stat '/home/anthony/Repositories/Anthony-Monterrosa/aws-postgres-node-stack/docker/data''.

So looks there is some operation before .dockerignore effect.

As there is no context content in your docker folder, I suggest you just add docker in .dockerignore.

This way, although still error, but the build will continue like next:

shubuntu1@shubuntu1:~/trial2020/trial$ docker build -t abcd:1 -f docker/Dockerfile .
ERRO[0000] Tar: Can't stat file /home/shubuntu1/trial2020/trial to tar: open 
/home/shubuntu1/trial2020/trial/docker/data: permission denied
Sending build context to Docker daemon  3.072kB
Step 1/1 : FROM ubuntu:18.04
 ---> 3556258649b2
Successfully built 3556258649b2
Successfully tagged abcd:1

UPDATE why according to your comments:

You may want to have a look for docker-ce source code, build.go & context.go:

build.go:

if err := build.ValidateContextDirectory(contextDir, excludes); err != nil {
    return errors.Errorf("error checking context: '%s'.", err)
}

context.go:

func ValidateContextDirectory(srcPath string, excludes []string) error {
    contextRoot, err := getContextRoot(srcPath)
    if err != nil {
        return err
    }

    pm, err := fileutils.NewPatternMatcher(excludes)
    if err != nil {
        return err
    }

    return filepath.Walk(contextRoot, func(filePath string, f os.FileInfo, err error) error {
        if err != nil {
            if os.IsPermission(err) {
                return errors.Errorf("can't stat '%s'", filePath)
            }
            if os.IsNotExist(err) {
                return errors.Errorf("file ('%s') not found or excluded by .dockerignore", filePath)
            }
            return err
        }

        // skip this directory/file if it's not in the path, it won't get added to the context
        if relFilePath, err := filepath.Rel(contextRoot, filePath); err != nil {
            return err
        } else if skip, err := filepathMatches(pm, relFilePath); err != nil {
            return err
        } else if skip {
            if f.IsDir() {
                return filepath.SkipDir
            }
            return nil
        }
......
    })
}

Before docker daemon tar the build context, it will first try to validate the context directory:

  1. docker/data in .dockerignore:

    It will use Walk to ergodic all things under docker, when it comes to docker/data, next code finally make the build exit, so you did not get image generated:

     if os.IsPermission(err) {
     return errors.Errorf("can't stat '%s'", filePath)
 }

  2. docker in .dockerignore:

    Same as above, difference is next code will effect when comes to the match docker in .dockerignore:

     return filepath.SkipDir

    This will make the Walk ignore the subfolders of docker, then docker/data no chance to be ergodic, so no permission error there.

    The ERRO[0000] Tar: Can't stat file comes from other later steps which won't exit the image build.

user_63947220
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