nomad/website/source/docs/drivers/rkt.html.md

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docs	Drivers: Rkt	docs-drivers-rkt	The rkt task driver is used to run application containers using rkt.

Rkt Driver

Name: rkt

The rkt driver provides an interface for using CoreOS rkt for running application containers.

Task Configuration

task "webservice" {
  driver = "rkt"

  config {
    image = "redis:3.2"
  }
}

The rkt driver supports the following configuration in the job spec:

• image - The image to run. May be specified by name, hash, ACI address or docker registry.

  config {
    image = "https://hub.docker.internal/redis:3.2"
  }
  

• command - (Optional) A command to execute on the ACI.

  config {
    command = "my-command"
  }
  

• args - (Optional) A list of arguments to the optional command. References to environment variables or any interpretable Nomad variables will be interpreted before launching the task.

  config {
    args = [
      "-bind", "${NOMAD_PORT_http}",
      "${nomad.datacenter}",
      "${MY_ENV}",
      "${meta.foo}",
    ]
  }
  

• trust_prefix - (Optional) The trust prefix to be passed to rkt. Must be reachable from the box running the nomad agent. If not specified, the image is run without verifying the image signature.

• dns_servers - (Optional) A list of DNS servers to be used in the container. Alternatively a list containing just host or none. host uses the host's resolv.conf while none forces use of the image's name resolution configuration.

• dns_search_domains - (Optional) A list of DNS search domains to be used in the containers.

• net - (Optional) A list of networks to be used by the containers

• port_map - (Optional) A key/value map of ports used by the container. The value is the port name specified in the image manifest file. When running Docker images with rkt the port names will be of the form ${PORT}-tcp. See networking below for more details.

   port_map {
           # If running a Docker image that exposes port 8080
           app = "8080-tcp"
   }
  

• debug - (Optional) Enable rkt command debug option.

• volumes - (Optional) A list of host_path:container_path strings to bind host paths to container paths.

  config {
    volumes = ["/path/on/host:/path/in/container"]
  }
  

Networking

The rkt can specify --net and --port for the rkt client. Hence, there are two ways to use host ports by using --net=host or --port=PORT with your network.

Example:

task "redis" {
	# Use rkt to run the task.
	driver = "rkt"

	config {
		# Use docker image with port defined
		image = "docker://redis:latest"
		port_map {
			app = "6379-tcp"
		}
	}

	service {
		port = "app"
	}

	resources {
		network {
			mbits = 10
			port "app" {
			    static = 12345
			}
		}
	}
}

Allocating Ports

You can allocate ports to your task using the port syntax described on the networking page.

When you use port allocation, the image manifest needs to declare public ports and host has configured network. For more information, please refer to rkt Networking.

Client Requirements

The rkt driver requires rkt to be installed and in your system's $PATH. The trust_prefix must be accessible by the node running Nomad. This can be an internal source, private to your cluster, but it must be reachable by the client over HTTP.

Client Configuration

The rkt driver has the following client configuration options:

• rkt.volumes.enabled: Defaults to true. Allows tasks to bind host paths (volumes) inside their container. Binding relative paths is always allowed and will be resolved relative to the allocation's directory.

Client Attributes

The rkt driver will set the following client attributes:

• driver.rkt - Set to 1 if rkt is found on the host node. Nomad determines this by executing rkt version on the host and parsing the output
• driver.rkt.version - Version of rkt eg: 1.1.0. Note that the minimum required version is 1.0.0
• driver.rkt.appc.version - Version of appc that rkt is using eg: 1.1.0

Here is an example of using these properties in a job file:

job "docs" {
  # Only run this job where the rkt version is higher than 0.8.
  constraint {
    attribute = "${driver.rkt.version}"
    operator  = ">"
    value     = "1.2"
  }
}

Resource Isolation

This driver supports CPU and memory isolation by delegating to rkt. Network isolation is not supported as of now.