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.

~> Experimental! Currently, the rkt driver supports launching containers but does not support dynamic ports. This can lead to port conflicts and as such, this driver is being marked as experimental and should be used with care.

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 containers.

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

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

• volumes - (Optional) A list of host_path:container_path strings to bind host paths to container paths. Can only be run on clients with the rkt.volumes.enabled option set to true.

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

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 false. Allows tasks to bind host paths (volumes) inside their container. Disabled by default as it removes the isolation between containers' data.

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.