ENV variable substitution no longer working in Dockerfiles?

[ocoleman-cordel]

VS Code version: 1.72.0
Dev Containers version: 0.255.3
Host operating system: Ubuntu 22.04
Docker version: 20.10.18

We have a base docker image that specifies an ENV variable for a user name. We build that docker image outside of vscode.
We then have a separate "dev" dockerfile that builds on this image that we open with the Dev Container extension. This "dev" dockerfile needs to use the ENV variable from the base image.

This has been working for us for a year or two now. A couple of days ago it stopped working, build/launch log attached.

If we replace the ENV variable with a hard-coded value in the "dev" dockerfile it works again. Perhaps ENV variable substitution is broken?

NOTE: once this error has occurred we have to remove the built images and containers from docker cache before a new working image can be built (eg with docker system prune). Probably not everything, but we wanted to be sure.

I made a minimal reproducible example, attached.

Steps to reproduce:

1. Extract the zip file into a new folder.
2. Build the base image with: docker build -t testbaseimage -f Dockerfile.base .
3. Open the new folder in vscode.
4. Run the Reopen in container command: it builds and opens without issue.
5. In .devcontainer/Dockerfile (the "dev" dockerfile referred to above):
   • uncomment the line # USER $MYUSER , and
   • comment out the line USER testuser
6. Run the Reopen in container command: it fails.

remoteContainers-2022-10-13T00-20-23.815Z.log
test.zip

[chrmarti]

Related: #7303

[chrmarti]

This should be fixed in Dev Containers 0.262.0-pre-release. Could you give that a try and let me know if it indeed fixes this issue? Thanks!

[rzhao271]

It works on 0.262.0. Thanks!