{{tag>nomad hashicorp volumes}}

====== Nomad volumes ======
===== Static volume =====
Define these on the client node.

<code>
# cat /etc/nomad/nomad.hcl 

data_dir  = "/var/lib/nomad"

bind_addr = "192.168.56.109"


client {
  enabled          = true
  servers          = ["192.168.56.105", "192.168.56.106", "192.168.56.107"]
  host_volume "my-data-volume" {
    path      = "/opt/hashicorp"
    read_only = false
  }
}

</code>

Restart nomad and use it in a job:

<code>
job "write‑file" {
  # Run the job once (no periodic scheduling)
  type = "batch"

  # Optional: limit the job to a single allocation
  datacenters = ["dc1"]
  group "writer" {
    count = 1

    task "create-file" {
      driver = "docker"

      config {
        # Small Alpine image with /bin/sh
        image = "alpine:latest"
        # The command that creates the file
        command = "/bin/sh"
        args    = ["-c", "echo 'Hello from Nomad!' > /custom/output.txt"]
      }

      # Mount a writable volume so the file persists after the container stops
      resources {
        cpu    = 100   # MHz
        memory = 64    # MB
      }

      # Define a host‑side volume (optional – if you want the file on the host)
      
       volume_mount {
         volume      = "example1"
         destination = "/custom"
         read_only   = false
       }
    }

    # Optional: define a named volume that maps to a host directory
     volume "example1" {
       type      = "host"
       source    = "my-data-volume"  
    }
  }
}
</code>

You will find the output at ''/opt/hashicorp/output.txt'' on a client node where this volume is defined.

===== Dynamic volumes =====

These can be created on any client and if constraints are not specified nomad will iterate over the available clients and [[https://developer.hashicorp.com/nomad/docs/other-specifications/volume/host#volume-placement|choose one to create]] it on.

<code>
# cat dyn-vol.hcl
name      = "example"
type      = "host"
plugin_id = "mkdir"

capability {
  access_mode     = "single-node-single-writer"
  attachment_mode = "file-system"
}

</code>

Create the volume

<code>
# nomad volume create dyn-vol.hcl
==> Created host volume example with ID ad332141-073f-cc90-8c39-a0bb470a4970
  ✓ Host volume "ad332141" ready

    2025-11-06T10:26:15Z
    ID        = ad332141-073f-cc90-8c39-a0bb470a4970
    Name      = example
    Namespace = default
    Plugin ID = mkdir
    Node ID   = 28105807-febd-505a-d0bb-006443663051
    Node Pool = default
    Capacity  = 0 B
    State     = ready
    Host Path = /var/lib/nomad/host_volumes/ad332141-073f-cc90-8c39-a0bb470a4970



# nomad volume status
Dynamic Host Volumes
ID        Name     Namespace  Plugin ID  Node ID   Node Pool  State
ad332141  example  default    mkdir      28105807  default    ready

</code>


This will create it somewhere at ''/var/lib/nomad/host_volumes/ad332141-073f-cc90-8c39-a0bb470a4970/'', the UUID will be different.

Use it in job

<code>
 job "write‑file" {
  # Run the job once (no periodic scheduling)
  type = "batch"

  # Optional: limit the job to a single allocation
  datacenters = ["dc1"]
  group "writer" {
    count = 1

    task "create-file" {
      driver = "docker"

      config {
        # Small Alpine image with /bin/sh
        image = "alpine:latest"
        # The command that creates the file
        command = "/bin/sh"
        args    = ["-c", "echo 'Hello from Nomad!' > /custom/output.txt"]
      }

      # Mount a writable volume so the file persists after the container stops
      resources {
        cpu    = 100   # MHz
        memory = 64    # MB
      }

      # Define a host‑side volume (optional – if you want the file on the host)
      # Uncomment the block below and adjust the path as needed.
      
       volume_mount {
         volume      = "example1"
        destination = "/custom"
         read_only   = false
       }
    }

    # Optional: define a named volume that maps to a host directory
     volume "example1" {
       type      = "host"
       source    = "example"  
       access_mode     = "single-node-single-writer"
       attachment_mode = "file-system"
    }
  }
}

</code>




====== Tested on ======
  * nomad 1.10.5
  * AlmaLinux release 9.6 (Sage Margay)

====== See also ======

====== References ======
  * https://blog.bitexpert.de/blog/nomad_dynamic_host_volumes
  * https://developer.hashicorp.com/nomad/docs/other-specifications/volume/host#nomad-dynamic-host-volume-specification