gcloud submit : specify Dockerfile with --file parameter doesn't seem to work

Question

In my project, Dockerfiles are not stored in the same place that the files I want to COPY in my image. Like :

root
     Dockerfiles:
          app_name1:
              dockerfile1
          ...
    folder
          app1
          app2
          ...
cloudbuild

I have a cloudbuild.yaml like that :

steps:
- name: gcr.io/cloud-builders/docker
  args:
  - build
  - '--tag=eu.gcr.io/$PROJECT_ID/${_IMAGE_NAME}:${_STAGE}'
  - **'-f ./Dockerfiles/${_IMAGE_NAME}/Dockerfile'**
  - .
images: [
    'eu.gcr.io/$PROJECT_ID/${_IMAGE_NAME}'
]

and I build the image from root like that :

gcloud builds submit .
      --config=cloudbuild.yaml
      --substitutions [...]
      .

I checked inside my GCP Bucket, the source specified in gcloud submit (.) is successfuly uploaded and so should be accessible in ./workspace/.

But the build fails with the following error :

unable to prepare context: unable to evaluate symlinks in Dockerfile path: lstat /workspace/ .: no such file or directory

It seems like he doesn't want to use the Dockerfile specified in the --file argument. And I can't manage to find an exemple of cloudbuild.yaml using this argument. Any idea on what's happening ?

Upon searching about what the error message means, I can see that the image creation process was trying to find the Dockerfile as it's based context for building the image but unable to do so. For more information about the error message, you can see this Stackoverflow link as a [guide](https://stackoverflow.com/questions/35511604/docker-unable-to-prepare-context-unable-to-evaluate-symlinks-in-dockerfile-pat). — Andie Vanille, Nov 23 '20 at 17:53
Yeah but using the -f argument should avoid this problem. I tested it locally and it worked well. — , Nov 24 '20 at 08:48

score 2 · Accepted Answer · answered Nov 23 '20 at 17:42

It's possibly that, if your file structure is accurate, you're referencing the Dockerfile path incorrectly.

A sanity check would be to run the docker build locally first:

PROJECT_ID="..."
_IMAGE_NAME="app1"
_STAGE="dev"

docker build \
--tag=gcr.io/$PROJECT_ID/${_IMAGE_NAME}:${_STAGE} \
--file=./Dockerfiles/${_IMAGE_NAME}/Dockerfile \
.

The following works for me:

.
├── cloudbuild.yaml
├── Dockerfiles
│   └── app1
│       └── Dockerfile
└── folder
    └── app1
        └── greeting.txt

And:

./Dockerfiles/app1/Dockerfile:

FROM busybox

WORKDIR /tmp

COPY ./folder/app1/greeting.txt ./greeting.txt

ENTRYPOINT ["cat","/tmp/greeting.txt"]

And:

cloudbuild.yaml:

steps:
  - name: docker
    args:
      - build
      - --tag=gcr.io/$PROJECT_ID/${_IMAGE_NAME}:${_STAGE}
      - --file=./Dockerfiles/${_IMAGE_NAME}/Dockerfile
      - .
images:
  - gcr.io/$PROJECT_ID/${_IMAGE_NAME}

And:

PROJECT="..."
QUESTION="64972175"
gcloud builds submit . \
--config=./cloudbuild.yaml \
--substitutions=_IMAGE_NAME=app1,_STAGE="dev" \
--project=${PROJECT}

Yields:

BUILD
Pulling image: docker
Using default tag: latest
latest: Pulling from library/docker
Digest: sha256:9170b902404a630a982a2a6473442d3e2cc2342b66345f7a9cf148f8affcf5d3
Status: Downloaded newer image for docker:latest
docker.io/library/docker:latest
Sending build context to Docker daemon  6.144kB
Step 1/4 : FROM busybox
latest: Pulling from library/busybox
Digest: sha256:a9286defaba7b3a519d585ba0e37d0b2cbee74ebfe590960b0b1d6a5e97d1e1d
Status: Downloaded newer image for busybox:latest
 ---> f0b02e9d092d
Step 2/4 : WORKDIR /tmp
 ---> Running in 6ffe8d2b3f56
Removing intermediate container 6ffe8d2b3f56
 ---> 51dcdc2e141a
Step 3/4 : COPY ./folder/app1/greeting.txt ./greeting.txt
 ---> 7459813216f3
Step 4/4 : ENTRYPOINT ["cat","/tmp/greeting.txt"]
 ---> Running in 25362a24391b
Removing intermediate container 25362a24391b
 ---> 398b1f4a60e2
Successfully built 398b1f4a60e2
Successfully tagged gcr.io/[[PROJECT]]/app1:dev
PUSH
Pushing gcr.io/[[PROJECT]]/app1
The push refers to repository [gcr.io/[[PROJECT]]/app1]
8b5d68988e85: Preparing
d2421964bad1: Preparing
d2421964bad1: Layer already exists
8b5d68988e85: Pushed
dev: digest: sha256:d33bd458b8df930fc3338110f8369743ac74068b8a527c5f59958ee1ce1182ff size: 734
DONE

Thank you for the detailed awnser ! I know why it didn't worked... In the cloudbuild.yaml, i wrote : `-f path` When I should have written `-f=path'. Stupid mistake... — , Nov 24 '20 at 08:57
You're welcome. You should be able to use a short flag (`-f value`) or a long flag (`--file=value`). Pleased to read the you got it working. Cloud Build is a really excellent service. — DazWilkin, Nov 24 '20 at 15:49

gcloud submit : specify Dockerfile with --file parameter doesn't seem to work

1 Answers1