Garden

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This topic describes Garden, the component that Cloud Foundry uses to create and manage isolated environments called containers. Each instance of an application deployed to Cloud Foundry runs within a container. For more information about how containers work, see the Container Mechanics section of the Understanding Container Security topic.

Backends

Garden has pluggable backends for different platforms and runtimes, and specifies a set of interfaces that each platform-specific backend must implement. These interfaces contain methods to perform the following actions:

• Create and delete containers
• Apply resource limits to containers
• Open and attach network ports to containers
• Copy files into and out of containers
• Run processes within containers
• Stream STDOUT and STDERR data out of containers
• Annotate containers with arbitrary metadata
• Snapshot containers for redeploys without downtime

For more information, see the Garden repository on GitHub.

Garden-runC

Cloud Foundry currently uses the Garden-runC backend, a Linux-specific implementation of the Garden interface using the Open Container Interface (OCI) standard. Previous versions of Cloud Foundry used the Garden-Linux backend.

Garden-runC has the following features:

• Uses the same OCI low-level container execution code as Docker and Kubernetes, so container images run identically across all three platforms
• AppArmor is configured and enforced by default for all unprivileged containers
• Seccomp whitelisting restricts the set of system calls a container can access, reducing the risk of container breakout
• Allows pluggable networking and rootfs management

For more information, see the Garden-runC repository on GitHub.

Garden RootFS (GrootFS)

Garden manages container filesystems through a plugin interface. Cloud Foundry uses the GrootFS plugin for this task. GrootFS is a Linux-specific implementation of the Garden volume plugin interface.

GrootFS performs the following actions:

• Creates container filesystems based on buildpacks and droplets
• Creates container filesystems based on remote docker images
• Authenticates with remote registries when using remote images
• Properly maps UID/GID for all files inside an image
• Executes garbage collection to remove unused volumes
• Applies per container disk quotas
• Provides per container disk usage stats

For more information, see Understanding GrootFS Disk Usage and the GrootFS repository on GitHub.