# Docker Build

Docker can be used to run the build inside a container. This is useful on non-Debian hosts (e.g. Fedora, Arch, macOS with Linux VM) or to keep the build environment isolated from the host system.

> **Note**: The Docker build is not fully isolated — it still needs kernel-level access for `binfmt_misc` (ARM emulation) and `losetup` (loop devices for `.img` builds).

## Building

```bash
cp config.example config   # edit as needed
./build-docker.sh
```

Output will be in `deploy/`.

## Continuing After a Failure

Edit the failing script, then resume without restarting from scratch:

```bash
CONTINUE=1 ./build-docker.sh
```

## Inspecting the Container After a Failure

```bash
sudo docker run -it --privileged --volumes-from=pigen_work vesperos-build /bin/bash
```

## Preserving the Container Between Runs

By default the container is removed after a successful build. To keep it for incremental development:

```bash
PRESERVE_CONTAINER=1 ./build-docker.sh
```

## Passing Extra Docker Arguments

Use `PIGEN_DOCKER_OPTS` to pass additional flags to `docker run`:

```bash
PIGEN_DOCKER_OPTS="--add-host myrepo:192.168.1.10" ./build-docker.sh
```

The `--name` and `--privileged` flags are already set by the script and should not be redefined.

## binfmt_misc on Docker Hosts

If building ARM images, `binfmt_misc` must be enabled on the host kernel before starting the build:

```bash
sudo apt-get install binfmt-support qemu-user-static
sudo update-binfmts --enable
```