Dockerfile 当我更改 FROM 图像时 COPY 命令停止工作

Question

I have two custom images. One is for developing websites using next.js and the other is to develop APIs.

My company/site image is like:

FROM node:lts-bullseye-slim

# the rest of it

And my company/api image is like:

ARG VARIANT="6.0-bullseye-slim"
FROM mcr.microsoft.com/vscode/devcontainers/dotnet:${VARIANT}

# the rest of it

The problem is that, the COPY commands works when I use company/api as my FROM image, but fails when I use company/site .

In other words, this works:

FROM company/api

COPY . .

RUN /buildScript.sh

But for the same directory, the same context, the same everything, this fails:

FROM compnay/site

COPY . .

RUN /buildScript.sh

In other words, COPY copies no file to the image. Everything is the same. There is no .dockerignore file. The same directory, the same context, the same syntax docker build -t company/api-or-site.

The only thing that causes this fail, is changing the base image.

What can cause this error? How can I debug this?

Answer 1

After spending days on this, I finally realized what the problem was.

When you create a custom image using a Dockerfile , if you use the WORKDIR command, then that would be the . in your future COPY commands.

Consider the following image:

FROM node:lts-bullseye-slim

# Your specific commands

WORKDIR /project

Let's say you build this image and tag it company/node .

Now if you want to use it as the base image for another image, and COPY. . COPY. . files, then those files would be copied to the /project directory.

FROM company/node

COPY . . # here, the second dot means the relative path inside the company/node image