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Garden-RunC Operator's Manual
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garden-runc-release

Garden-RunC Operator's Manual

Overview

Garden is a cross-platform API for managing containers using containerization technologies like containerd, runc or winc.

Note: For historical reasons, the garden bosh release is called "garden-runc-release" although it may be deployed with any containerization backend.

Containerd or Runc?

When operating Garden on Linux it is important to understand that it can run in one of two modes - runc mode and containerd mode.

Important: Containerd mode is the default for cf-deployment above v6.2.0. You can opt back into runc mode by using the cf-deployment/use-native-garden-runc-runner.yml ops file.

How do I know which mode I'm using

It is easy to determine the Garden mode of your deployment. You are using containerd if any of these conditions are satisfied:

  • The deployment manifest defines a job named containerd
  • The job named garden has the containerd_mode property set to true

If none of the above conditions hold you are using runc.

Based on the configuration of your deployment you can find more details in the respective ops guides:

Garden Components

Guardian consists of three primary "modules", these are the Networker, the Volumizer and the Containerizer.

Volumizer

The default component used by Garden to manage rootfs volumes is called GrootFS. Garden allows the volumizer to be overridden by specifying the image_plugin family of BOSH properties.

The Graph

The graph stores the filesystem layers which make up the root filesystem images for containers. In the case of docker images these are downloaded from a remote docker registry. In the case of "preloaded" root filesystems these are imported from a path on disk.

To determine which path in the graph is being used as the root filesystem of a particular container, you can look for the "rootfs" property inside RunC's bundle config, the config.json file. Here is how to find this file in containerd mode and in runc mode.

Garden's rootfs layer management is handled by a component called GrootFS which stores its graphs at /var/vcap/data/grootfs/store/{unprivileged,privileged}. To understand more about graph disk usage with GrootFS, refer to this doc.

GrootFS

The GrootFS module implements the image_plugin contract. GrootFS is the built-in root filesystem management component which is used by default. GrootFS uses overlay to efficiently combine filesystem layers, along with an xfs base filesystem mounted with a loop device to implement disk quotas.

Garden-Shed

Garden-Shed is the deprecated root filesystem management component, which has now been removed in versions above 1.16.8.

Networker

The default component used by Garden to manage networks is called Kawasaki. Garden allows the networker to be overridden by specifying the network_plugin family of BOSH properties.

Kawasaki

Kawasaki is Guardian's built-in networking component, used by default and if no network_plugin is configured. Kawasaki is invoked to configure the network of a created container before any user processes are run.

External networker

The container-to-container networking project implements the network_plugin contract.

Configuring CPU entitlement

Nomenclature

  • garden-runc-release: the bosh release for this project
  • garden: the API, sometimes refers to guardian
  • guardian (also, gdn): the server handling API requests