Docker build fails with: unbound variable on darwin

[half2me]

Steps to reproduce:

git clone --depth 1 https://github.com/RPI-Distro/pi-gen.git
cd pi-gen
echo "IMG_NAME=Foo" > config
./build-docker.sh

I get the following error: ./build-docker.sh: line 147: DOCKER_CMDLINE_PRE[@]: unbound variable

Output of docker --version

Client:
 Cloud integration: v1.0.35-desktop+001
 Version:           24.0.5
 API version:       1.43
 Go version:        go1.20.6
 Git commit:        ced0996
 Built:             Fri Jul 21 20:32:30 2023
 OS/Arch:           darwin/arm64
 Context:           desktop-linux

Server: Docker Desktop 4.22.0 (117440)
 Engine:
  Version:          24.0
  API version:      1.43 (minimum version 1.12)
  Go version:       go1.20.6
  Git commit:       HEAD
  Built:            Sun Jul 30 02:09:41 2023
  OS/Arch:          linux/arm64
  Experimental:     false
 containerd:
  Version:          1.6.21
  GitCommit:        3dce8eb055cbb6872793272b4f20ed16117344f8
 runc:
  Version:          1.1.7
  GitCommit:        v1.1.7-0-g860f061
 docker-init:
  Version:          0.19.0
  GitCommit:        de40ad0

[reubenmiller]

This problem happens because MacOS has a very old version of bash by default which is missing some more "modern" features like arrays. Currently the default version is "3.2.57", where as iirc arrays was added to bash in >= 4.x.

1. Install a newer version of bash (e.g. using homebrew). Afterwards make sure it is included in the PATH variable before the /bin folder. Though you can see information online for further instructions if you run into problems installing it

2. Replace the shebang in the build-docker.sh script to the following:

   #!/usr/bin/env bash
   set -eu

Though you might run into some follow up problems (I'm currently doing the same thing and try to debug as I go).

Update

I was able to build the images with the above tweak to the build-docker.sh script on my MacOS M1, though you need to checkout the arm64 branch! This is mentioned in the troubleshooting section of the docs, but I overlooked it at the beginning. Below shows how to clone the project's arm64 branch (taken from the README.md)

git clone --branch arm64 https://github.com/RPI-Distro/pi-gen.git

[reubenmiller]

FYI: I've created a PR to the arm64 branch with a change to the build-docker.sh script to support running on MacOS with the default version of bash (e.g. version 3.x).

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