easyto-init

The init system for easyto.

This is PID 1 inside an easyto-built AMI. On boot, it:

• Mounts the early filesystems (/, devtmpfs, proc, sysfs, cgroup2, etc).
• Reads container metadata baked into the AMI, derived from the container image the AMI was built from. This contains the default command or entrypoint, environment variables, working directory, etc.
• Brings up networking on the primary EC2 interface.
• Retrieves the instance's user data from IMDS. The user data can contain overrides for the container metadata and other configuration, such as external sources for environment variables and files.
• Resolves environment variables or files from S3, SSM, or Secrets Manager.
• Formats and mounts any configured EBS volumes. Optionally, it will first attach external EBS volumes that match specified tags.
• Loads kernel modules.
• Sets sysctls.
• Runs init scripts defined in user data.
• Runs the configured command as a process supervised by easyto-init, or via execve() (by setting replace-init: true in user data). Note that the latter option will not perform a clean shutdown when the EC2 instance is terminated unless your command knows how to do so.

The user data is a YAML document that can be seen under tests/integration/scenarios/; see basic-boot for the smallest example and env-from-imds or secrets-manager-env-from for environment variable resolution from AWS sources.

Building

make build
make release VERSION=v0.x.y

Testing

make test                                      # Run unit tests.
make test-integration-kvm                      # Run the full integration test suite.
make test-integration-kvm SCENARIO=basic-boot  # Run one integration scenario.

Integration tests run scenarios inside QEMU/KVM with a mock IMDS server and (where needed) LocalStack for S3/SSM/Secrets Manager.