I'm trying to create Go web server into small Docker images. Ideally the clean image contains only the Go application itself (and maybe supporting web components, but not the Go-building environment).
Here is my Dockerfile:
# golang:latest as build-env
FROM golang:latest AS build-env
RUN mkdir /app
ADD . /app/
WORKDIR /app
RUN cd /app && GO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o myapp .
# go build -o myapp
FROM scratch
COPY --from=build-env /app/myapp /app/images /
EXPOSE 8080
ENTRYPOINT /myapp
It uses the Docker Builder Pattern and scratch image, which is a special docker image that's empty.
It builds OK, but when I run it, I'm getting:
docker: Error response from daemon: OCI runtime create failed: container_linux.go:344: starting container process caused "exec: \"/bin/sh\": stat /bin/sh: no such file or directory": unknown.
UPDATE:
So the ENTRYPOINT need to be changed to the exec form:
ENTRYPOINT ["/myapp"]
Having done that, I'm getting a new error:
standard_init_linux.go:207: exec user process caused "no such file or directory"
Having use a small footprint Linux image as the base (i.e. Alpine Linux) instead of scratch wouldn't help either:
$ docker run -it -p 8080:8080 go-web-docker-small
standard_init_linux.go:207: exec user process caused "no such file or directory"
$ docker run -it -p 8080:8080 go-web-docker-small /bin/sh -i
standard_init_linux.go:207: exec user process caused "no such file or directory"
How to fix it? Thx!
While building Dockerfile provided by you, I am getting following error:
COPY failed: stat /var/lib/docker/overlay2/cc1f8144192760ce7bf9cda7a7dfd0af16065901594c38609c813ea103cfd8d7/merged/app/images: no such file or directory
Fixed copy command and few others and image is building with following in Dockerfile
# golang:latest as build-env
FROM golang:latest AS build-env
RUN mkdir /app
ADD . /app/
WORKDIR /app
RUN cd /app && GO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o myapp .
# go build -o myapp
FROM scratch
COPY --from=build-env /app/myapp .
EXPOSE 8080
ENTRYPOINT ["./myapp"]
The last line of your Dockerfile is
ENTRYPOINT /myapp
There are two forms of the ENTRYPOINT (and CMD and RUN) instructions. An "exec form" looks like a JSON list, and provides an uninterpreted list of arguments to run as the main container process. A "shell form" does not look like a JSON list, and is implicitly wrapped in /bin/sh -c '...'.
Your ENTRYPOINT uses the shell form, and a FROM scratch image doesn't have a shell, producing the error you get. You can change this to the exec form
ENTRYPOINT ["/myapp"]