open-nomad/website/content/docs/job-specification/volume_mount.mdx

---
layout: docs
page_title: volume_mount Block - Job Specification
description: |-
  The "volume_mount" block allows the task to specify where a group "volume"
  should be mounted.
---

# `volume_mount` Block

<Placement groups={['job', 'group', 'task', 'volume_mount']} />

The `volume_mount` block allows the task to specify how a group
[`volume`][volume] should be mounted into the task.

```hcl
job "docs" {
  group "example" {
    volume "certs" {
      type = "host"
      read_only = true
      source = "ca-certificates"
    }

    task "example" {
      volume_mount {
        volume      = "certs"
        destination = "/etc/ssl/certs"
        propagation_mode = "private"
      }
    }
  }
}
```

The Nomad client will make the volumes available to tasks according to this
configuration, and it will fail the allocation if the client configuration
updates to remove a volume that it depends on.

## `volume_mount` Parameters

- `volume` `(string: "")` - Specifies the group volume that the mount is going
  to access.

- `destination` `(string: "")` - Specifies where the volume should be mounted
  inside the task's allocation.

- `read_only` `(bool: false)` - When a group volume is writeable, you may
  specify that it is `read_only` on a per mount level using the `read_only`
  option here.

- `propagation_mode` `(string: "private")` - Specifies the mount propagation
  mode for nested volumes. Possible values are:

    - `private` - the task is not allowed to access nested mounts.

    - `host-to-task` - allows new mounts that have been created outside of the
    task to be visible inside the task.

    - `bidirectional` - allows the task to both access new mounts from the host
    and also create new mounts. This mode requires `ReadWrite` permission.

    ~> **Warning:** `bidirectional` propagation mode can be dangerous to use
    and cause problems in the host operating system if a task creates a mount
    but does not clean it up properly before exiting.

For examples of how to use [HCL2] interpolation for fine-grained control of
volumes, see [Volume Interpolation].

[volume]: /nomad/docs/job-specification/volume 'Nomad volume Job Specification'
[volume interpolation]: /nomad/docs/job-specification/volume#volume-interpolation
[hcl2]: /nomad/docs/job-specification/hcl2