fix init_container script, fix container file ownership, add container info to readme.

Author: FoamyGuy

ports/zephyr-cp/README.md

@@ -28,6 +28,33 @@ make BOARD=nordic_nrf7002dk
 This uses Zephyr's cmake to generate Makefiles that then delegate to
 `tools/cpbuild/build_circuitpython.py` to build the CircuitPython bits in parallel.
 
+## Native simulator build container
+
+Building the native sim requires `libsdl2-dev:i386` and other 32bit dependencies that
+can cause conflicts on 64bit systems resulting in the removal of 64bit versions of critical
+software such as the display manager and network manager. A Containerfile and a few scripts
+are provided to set up a container to make the native sim build inside without affecting the
+host system.
+
+The container automatically mounts this instance of the circuitpython repo inside at
+`/home/dev/circuitpython`. Changes made in the repo inside the container and on the host PC
+will sync automatically between host and container.
+
+To use the container file:
+
+1. Build the container with `podman build -t zephyr-cp-dev -f native_sim_build_Containerfile .`
+2. Run/Start the container by running `./native_sim_build_run_container.sh` on the host PC.
+   The script will automatically run or start based on whether the container has been run before.
+3. Init requirements inside the container with `./native_sim_build_init_container.sh`
+
+To delete the container and cleanup associated files:
+```sh
+podman ps -a --filter ancestor=zephyr-cp-dev -q | xargs -r podman rm -f
+podman rmi zephyr-cp-dev
+podman image prune -f
+podman rm -f zcp
+```
+
 ## Running the native simulator
 
 From `ports/zephyr-cp`, run:

ports/zephyr-cp/native_sim_build_Containerfile

@@ -12,7 +12,10 @@ RUN dpkg --add-architecture i386 && apt-get update && apt-get install -y --no-in
         protobuf-compiler sudo \
     && rm -rf /var/lib/apt/lists/*
 
-RUN useradd -m -s /bin/bash dev \
+# Remove the default ubuntu:24.04 'ubuntu' user (UID 1000) so 'dev' can take
+# UID 1000 — required for --userns=keep-id to map host UID 1000 to 'dev'.
+RUN userdel -r ubuntu 2>/dev/null || true \
+ && useradd -m -u 1000 -s /bin/bash dev \
  && echo 'dev ALL=(ALL) NOPASSWD:ALL' > /etc/sudoers.d/dev \
  && chmod 440 /etc/sudoers.d/dev
 USER dev

ports/zephyr-cp/native_sim_build_init_container.sh

@@ -9,10 +9,12 @@
 # Safe to re-run; west/pip/etc. are idempotent.
 set -euo pipefail
 
+git config --global --add safe.directory /home/dev/circuitpython
+
 cd "$(dirname "${BASH_SOURCE[0]}")"
 
 echo "==> west init"
-if [ ! -d ../../.west ]; then
+if [ ! -d .west ]; then
     west init -l zephyr-config
 else
     echo "    (already initialized, skipping)"
@@ -34,7 +36,6 @@ echo "==> west sdk install (x86_64-zephyr-elf)"
 west sdk install -t x86_64-zephyr-elf
 
 echo "==> fetch port submodules"
-git config --global --add safe.directory /home/dev/circuitpython
 python ../../tools/ci_fetch_deps.py zephyr-cp
 
 echo