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Docker Configuration

Kismatic supports docker as the underlying container runtime for your cluster. During the installation of your cluster, Kismatic will download and install docker on all nodes except etcd nodes.

Storage in RHEL/CentOS (KET v1.3.1+)

The default storage driver that gets installed on RHEL/CentOS is devicemapper in loop-lvm mode. However, this is not recommended for production setups. Instead, devicemapper must be setup in direct-lvm mode.

The direct-lvm mode requires a block storage device that will be used exclusively for docker's storage needs. For this reason, this is an opt-in feature that can be enabled in the plan file:

docker:
  storage:
    direct_lvm:                          # Configure devicemapper in direct-lvm mode (RHEL/CentOS only).
      enabled: false
      block_device: ""                   # Path to the block device that will be used for direct-lvm mode. This device will be wiped and used exclusively by docker.
      enable_deferred_deletion: false    # Set to true if you want to enable deferred deletion when using direct-lvm mode.

When direct-lvm is enabled, Kismatic will create a logical volume configured as a thin pool to use as the backing storage for docker. Creating a thin pool logical volume requires a "data" logical volume and a "metadata" logical volume.

The provided block storage device will be split 95% for data, and 1% for metadata, as recommended by Docker. The remaining space allows for auto-extending the logical volumes when they start to fill up as a temporary stop gap. The threshold for auto-extension is set to 80% of the size of the volume.

For more information on devicemapper see https://docs.docker.com/engine/userguide/storagedriver/device-mapper-driver/#configure-direct-lvm-mode-for-production