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GrootFS (BOSH release)

DEPRECATED. grootfs-release has been merged into garden-runc-release.

A BOSH release for deploying GrootFS.

This release makes a lot of assumptions based on expected use with garden-runc-release in the context of Cloud Foundry / Diego. It may be useful in combination with Garden-runC outside of Cloud Foundry, but it's unlikely to be useful in any other context.

Deploying with Diego / Cloud Foundry

There are two possible approaches to add GrootFS to an existing CF/Diego deployment. Choose the one which suits your needs best:

Using the new BOSH Operations File feature

Our supported way to add GrootFS to a Cloud Foundry / Diego deployment is by applying a GrootFS BOSH Operations file to your existing Diego deployment manifest. In order to use operations files, you will need to use the new Golang-based BOSH CLI.

The GrootFS operations file is located in cf-deployment: operations/experimental/use-grootfs.yml. It contains a description of the manifest changes BOSH needs to make to your existing deployment in order to add GrootFS. You may need to edit the file to ensure that the referenced job names match those in your existing CF / Diego deployment. Once you've checked this, run:

bosh deploy \
  --ops-file operations/experimental/use-grootfs.yml \

Modifying manifests manually

If you don't want to use the operations file approach, you can alternatively make the equivalent changes to you deployment manifests manually.

Given an existing Diego / CF deployment, take the following steps to add grootfs-release to the cells in your Diego deployment:

  • Select a version of grootfs-release - you can find the compatible version of grootfs-release for your version of garden-runc-release in the Garden-runC release notes
  • Add grootfs-release to the releases section of your deployment manifest (and upload grootfs-release to your BOSH director)
  • Add the grootfs job to the templates section of your cell job
  • Add the following properties to your cell job
  image_plugin: "/var/vcap/packages/grootfs/bin/grootfs"
  image_plugin_extra_args: ["--config=/var/vcap/jobs/grootfs/config/grootfs_config.yml"]

  # if you have capi.nsync.diego_privileged_containers and capi.stager.diego_privileged_containers set to true
  privileged_image_plugin: "/var/vcap/packages/grootfs/bin/grootfs"
  privileged_image_plugin_extra_args: ["--config=/var/vcap/jobs/grootfs/config/privileged_grootfs_config.yml"]
  • Set the diego.rep.preloaded_rootfses property on your Diego cells to [cflinuxfs2:/var/vcap/packages/cflinuxfs2/rootfs.tar]. Make sure you're using version 1.45.0 or later of cflinuxfs2-rootfs-release, otherwise the rootfs tarball will not be present on disk on the cells. If you are using a custom rootfs, you'll need to start providing that as a tarball, and set this property accordingly.

If you have set any of the following garden properties, you should set them on grootfs to get the same behaviour:

  • graph_cleanup_threshold_in_mb
  • insecure_docker_registry_list
  • persistent_image_list (change directory paths to tarballs - e.g. /var/vcap/packages/cflinuxfs2/rootfs.tar)

There is no equivalent to the garden.docker_registry_endpoint property. If you need this, GrootFS may not be suitable for you yet. Please open an issue and let us know your use case though!

You may also want to set the following optional properties on grootfs for various reasons. See the grootfs job spec for more info on what these properties do:

  • dropsonde_port
  • log_level
  • driver
  • skip_mount

There should be no need to recreate cells when transitioning to GrootFS, though you may wish to do so anyway in order to clear out any cruft left behind by Garden-runC's previous image management implementation.


By default the grootfs-release will consume the rootless_link produced by garden-runc-release when it's available. This is used to enable the rootless experimental feature on grootfs, enabling it to run as an unprivileged user.

Normally there's no extra step to be taken when configuring grootfs here, it will deploy accordingly to garden's configuration.

But in case you have more than one job producing the link (e.g. multiple diego-cell types), you'll need to implicitly produce and consume the links for each of them. For example:

- name: diego-cell-z1
  - name: grootfs
    release: grootfs
      rootless_link: {from: garden-rootless-link-z1}
  - name: garden
    release: garden-runc
      rootless_link: {as: garden-rootless-link-z1}
- name: diego-cell-z2
  - name: grootfs
    release: grootfs
      rootless_link: {from: garden-rootless-link-z2}
  - name: garden
    release: garden-runc
      rootless_link: {as: garden-rootless-link-z2}

This will allow bosh to know which link to consume, and make sure that it's the one produced by the collocated garden-runc release.


It's possible to chose a filesystem driver to use by providing the grootfs.driver property in the manifest. The default driver is btrfs, and the other possible value for this property is overlay-xfs.

At this moment it's not supported to change the driver of a running instance. The vm must be recreated.


newuidmap / newgidmap

We ship custom implementations of newuidmap and newgidmap that ignore /etc/subuid and /etc/subgid. These custom binaries have a specific uid/gid mapping hard coded. Currently, Garden-runC only ever uses one this one specific mapping. Hard coding the mapping reduces the possible attack surface for exploits, which we care about since these binaries execute as root. The usual approach of describing allowed mappings in /etc/sub{u,g}id doesn't play very nicely with BOSH.

volume creation

Depending on the driver property, the release will create a btrfs or xfs volumes. The release will never recreate this volume on an update if the file already exists. Current flow:

  • If there's no volume file: create volume file -> format with btrfs/xfs -> mount
  • If there's a volume file: check if it's formatted with btrfs/xfs
    • if yes -> mount
    • if no -> format with btrfs/xfs -> mount

Two volumes will be created, one for privileged and one for unprivileged containers, they will have a sparse file of the size of the parent disk as the backing store device.

Even though garden will be calling grootfs as root, the unprivileged store will be owned by the user ~4294967294 (or the max uid possible), in order to allow the running user of the container to have access to it's filesystem.


In order to help us extend GrootFS, we recommend opening a Github issue to describe the proposed features or changes. We also welcome pull requests.


  1. Multiple instance groups provide links of type 'garden_rootless_link':
L Error: Unable to process links for deployment. Errors are:
  - Multiple instance groups provide links of type 'garden_rootless_link'. Cannot decide which one to use for instance group 'garden-btrfs'.
  - Multiple instance groups provide links of type 'garden_rootless_link'. Cannot decide which one to use for instance group 'garden-overlay-xfs'.

Check garden rootless link


Apache License 2.0