Building the project

To build the container project, you need:

Mac with Apple silicon
macOS 15 minimum, macOS 26 recommended
Xcode 26, set as the active developer directory

[!IMPORTANT] There is a bug in the vmnet framework on macOS 26 that causes network creation to fail if the container helper applications are located under your Documents or Desktop directories. If you use make install, you can simply run the container binary in /usr/local. If you prefer to use the binaries that make all creates in your project bin and libexec directories, locate your project elsewhere, such as ~/projects/container, until this issue is resolved.

Compile and test

Build container and the background services from source, and run basic and integration tests:

bash

make all test integration

Copy the binaries to /usr/local/bin and /usr/local/libexec (requires entering an administrator password):

bash

make install

Or to install a release build, with better performance than the debug build:

bash

BUILD_CONFIGURATION=release make all test integration
BUILD_CONFIGURATION=release make install

Compile protobufs

container uses gRPC to communicate to the builder virtual machine that creates images from Dockerfiles, and depends on specific versions of grpc-swift and swift-protobuf. If you make changes to the gRPC APIs in the container-builder-shim project, install the tools and re-generate the gRPC code in this project using:

bash

make protos

Develop using a local copy of Containerization

To make changes to container that require changes to the Containerization project, or vice versa:

Clone the Containerization repository such that it sits next to your clone of the container repository. Ensure that you follow containerization instructions to prepare your build environment.
In your development shell, go to the container project directory.
bash
```
cd container
```
If the container services are already running, stop them.
bash
```
bin/container system stop
```
Reconfigure the Swift project to use your local containerization package and update your Package.resolved file.
bash
```
/usr/bin/swift package edit --path ../containerization containerization
/usr/bin/swift package update containerization
```
[!IMPORTANT] If you are using Xcode, do not run swift package edit. Instead, temporarily modify Package.swift to replace the versioned containerization dependency:
swift
```
.package(url: "https://github.com/apple/containerization.git", exact: Version(stringLiteral: scVersion)),
```
with the local path dependency:
swift
```
.package(path: "../containerization"),
```
Note: If you have already run swift package edit, whether intentionally or by accident, follow the steps in the next section to restore the normal containerization dependency. Otherwise, the modified Package.swift file will not work, and the project may fail to build.
If you want container to use any changes you made in the vminit subproject of Containerization, update the system property to use the locally built init filesystem image:
bash
```
container system property set image.init vminit:latest 
```
Build container.
```
make clean all
```

Restart the container services.

bin/container system stop
bin/container system start

To revert to using the Containerization dependency from your Package.swift:

If you were using the local init filesystem, revert the system property to its default value:
bash
```
container system property clear image.init
```
Use the Swift package manager to restore the normal containerization dependency and update your Package.resolved file. If you are using Xcode, revert your Package.swift change instead of using swift package unedit.
bash
```
/usr/bin/swift package unedit containerization
/usr/bin/swift package update containerization
```
Rebuild container.
bash
```
make clean all
```

Restart the container services.

bash

bin/container system stop
bin/container system start

Develop using a local copy of container-builder-shim

To test changes that require the container-builder-shim project:

Clone the container-builder-shim repository and navigate to its directory.
After making the necessary changes, build the custom builder image, set it as the active builder image, and remove the existing buildkit container so the new image will be used:

bash

container build -t builder .
container system property set image.builder builder:latest
container rm -f buildkit

Run the container build as usual:

bash

container build ...

[!IMPORTANT] If your modified builder image is broken, make sure to rebuild and correctly tag the builder image before attempting to build container-builder-shim again.

Debug XPC Helpers

Attach debugger to the XPC helpers using their launchd service labels:

Find launchd service labels:

console

% container system start
% container run -d --name test debian:bookworm sleep infinity
test
% launchctl list | grep container
27068   0       com.apple.container.container-network-vmnet.default
27072   0       com.apple.container.container-core-images
26980   0       com.apple.container.apiserver
27331   0       com.apple.container.container-runtime-linux.test

Stop container and start again after setting the environment variable CONTAINER_DEBUG_LAUNCHD_LABEL to the label of service to attach debugger. Services whose label starts with the CONTAINER_DEBUG_LAUNCHD_LABEL will wait the debugger:

console

% export CONTAINER_DEBUG_LAUNCHD_LABEL=com.apple.container.container-runtime-linux.test
% container system start # Only the service `com.apple.container.container-runtime-linux.test` waits debugger

console

% export CONTAINER_DEBUG_LAUNCHD_LABEL=com.apple.container.container-runtime-linux
% container system start # Every service starting with `com.apple.container.container-runtime-linux` waits debugger

Run the command to launch the service, and attach debugger:

console

% container run -it --name test debian:bookworm
⠧ [6/6] Starting container [0s] # It hangs as the service is waiting for debugger

Pre-commit hook

Run make pre-commit to install a pre-commit hook that ensures that your changes have correct formatting and license headers when you run git commit.