open-nomad/website/source/docs/job-specification/task.html.md

---
layout: "docs"
page_title: "task Stanza - Job Specification"
sidebar_current: "docs-job-specification-task"
description: |-
  The "task" stanza creates an individual unit of work, such as a Docker
  container, web application, or batch processing.
---

# `task` Stanza

<table class="table table-bordered table-striped">
  <tr>
    <th width="120">Placement</th>
    <td>
      <code>job -> group -> **task**</code>
    </td>
  </tr>
</table>
The `task` stanza creates an individual unit of work, such as a Docker
container, web application, or batch processing.

```hcl
job "docs" {
  group "example" {
    task "server" {
      # ...
    }
  }
}
```

## `task` Parameters

- `artifact` <code>([Artifact][]: nil)</code> - Defines an artifact to download
  before running the task. This may be specified multiple times to download
  multiple artifacts.

- `config` `(map<string|string>: nil)` - Specifies the driver configuration,
  which is passed directly to the driver to start the task. The details of
  configurations are specific to each driver, so please see specific driver
  documentation for more information.

- `constraint` <code>([Constraint][]: nil)</code> - Specifies user-defined
  constraints on the task. This can be provided multiple times to define
  additional constraints.

- `affinity` <code>([Affinity][]: nil)</code> - This can be provided
  multiple times to define preferred placement criteria.

- `dispatch_payload` <code>([DispatchPayload][]: nil)</code> - Configures the
  task to have access to dispatch payloads.

- `driver` - Specifies the task driver that should be used to run the
  task. See the [driver documentation](/docs/drivers/index.html) for what
  is available. Examples include `docker`, `qemu`, `java` and `exec`.

- `env` <code>([Env][]: nil)</code> - Specifies environment variables that will
  be passed to the running process.

- `kill_timeout` `(string: "5s")` - Specifies the duration to wait for an
  application to gracefully quit before force-killing. Nomad sends an `SIGINT`.
  If the task does not exit before the configured timeout, `SIGKILL` is sent to
  the task. Note that the value set here is capped at the value set for
  [`max_kill_timeout`][max_kill] on the agent running the task, which has a
  default value of 30 seconds.

- `kill_signal` `(string)` - Specifies a configurable kill signal for a task,
  where the default is SIGINT. Note that this is only supported for drivers
  sending signals (currently `docker`, `exec`, `raw_exec`, and `java` drivers).

- `leader` `(bool: false)` - Specifies whether the task is the leader task of
  the task group. If set to true, when the leader task completes, all other
  tasks within the task group will be gracefully shutdown.

- `logs` <code>([Logs][]: nil)</code> - Specifies logging configuration for the
  `stdout` and `stderr` of the task.

- `meta` <code>([Meta][]: nil)</code> - Specifies a key-value map that annotates
  with user-defined metadata.

- `resources` <code>([Resources][]: <required>)</code> - Specifies the minimum
  resource requirements such as RAM, CPU and network.

- `service` <code>([Service][]: nil)</code> - Specifies integrations with
  [Consul][] for service discovery. Nomad automatically registers when a task
  is started and de-registers it when the task dies.

- `shutdown_delay` `(string: "0s")` - Specifies the duration to wait when
  killing a task between removing it from Consul and sending it a shutdown
  signal. Ideally services would fail healthchecks once they receive a shutdown
  signal. Alternatively `shutdown_delay` may be set to give in flight requests
  time to complete before shutting down.

- `user` `(string: <varies>)` - Specifies the user that will run the task.
  Defaults to `nobody` for the [`exec`][exec] and [`java`][java] drivers.
  [Docker][] and [rkt][] images specify their own default users.  This can only
  be set on Linux platforms, and clients can restrict
  [which drivers][user_drivers] are allowed to run tasks as
  [certain users][user_blacklist].

- `template` <code>([Template][]: nil)</code> - Specifies the set of templates
  to render for the task. Templates can be used to inject both static and
  dynamic configuration with data populated from environment variables, Consul
  and Vault.

- `vault` <code>([Vault][]: nil)</code> - Specifies the set of Vault policies
  required by the task. This overrides any `vault` block set at the `group` or
  `job` level.

## `task` Examples

The following examples only show the `task` stanzas. Remember that the
`task` stanza is only valid in the placements listed above.

### Docker Container

This example defines a task that starts a Docker container as a service. Docker
is just one of many drivers supported by Nomad. Read more about drivers in the
[Nomad drivers documentation](/docs/drivers/index.html).

```hcl
task "server" {
  driver = "docker"
  config {
    image = "hashicorp/http-echo"
    args  = ["-text", "hello world"]
  }

  resources {
    network {
      mbits = 250
    }
  }
}
```

### Metadata and Environment Variables

This example uses custom metadata and environment variables to pass information
to the task.

```hcl
task "server" {
  driver = "exec"
  config {
    command = "/bin/env"
  }

  meta {
    my-key = "my-value"
  }

  env {
    MY_KEY = "${meta.my-key}"
  }

  resources {
    cpu = 20
  }
}
```

### Service Discovery

This example creates a service in Consul. To read more about service discovery
in Nomad, please see the [Nomad service discovery documentation][service_discovery].

```hcl
task "server" {
  driver = "docker"
  config {
    image = "hashicorp/http-echo"
    args  = ["-text", "hello world"]
  }

  service {
    tags = ["default"]

    check {
      type     = "tcp"
      interval = "10s"
      timeout  = "2s"
    }
  }

  resources {
    cpu = 20
  }
}
```

[artifact]: /docs/job-specification/artifact.html "Nomad artifact Job Specification"
[consul]: https://www.consul.io/ "Consul by HashiCorp"
[constraint]: /docs/job-specification/constraint.html "Nomad constraint Job Specification"
[affinity]: /docs/job-specification/affinity.html "Nomad affinity Job Specification"
[dispatchpayload]: /docs/job-specification/dispatch_payload.html "Nomad dispatch_payload Job Specification"
[env]: /docs/job-specification/env.html "Nomad env Job Specification"
[meta]: /docs/job-specification/meta.html "Nomad meta Job Specification"
[resources]: /docs/job-specification/resources.html "Nomad resources Job Specification"
[logs]: /docs/job-specification/logs.html "Nomad logs Job Specification"
[service]: /docs/job-specification/service.html "Nomad service Job Specification"
[vault]: /docs/job-specification/vault.html "Nomad vault Job Specification"
[exec]: /docs/drivers/exec.html "Nomad exec Driver"
[java]: /docs/drivers/java.html "Nomad Java Driver"
[Docker]: /docs/drivers/docker.html "Nomad Docker Driver"
[rkt]: /docs/drivers/rkt.html "Nomad rkt Driver"
[service_discovery]: /guides/operations/consul-integration/index.html#service-discovery/index.html "Nomad Service Discovery"
[template]: /docs/job-specification/template.html "Nomad template Job Specification"
[user_drivers]: /docs/configuration/client.html#_quot_user_checked_drivers_quot_
[user_blacklist]: /docs/configuration/client.html#_quot_user_blacklist_quot_
[max_kill]: /docs/configuration/client.html#max_kill_timeout