Enabling pre-Nomad 0.12 Docker mount behavior for dev agents

docker.md

Create a configuration file and a sample job.

docker.hcl

plugin "docker" { 
  config {
     volumes {
       enabled = true
     } 
  }
}

example.nomad

job "example" {
  datacenters = ["dc1"]

  group "cache" {
    task "redis" {
      driver = "docker"

      config {
        image = "redis:3.2"
        # this is an arbitrary path on my client not exposed in any way
        volumes = ["/opt/nomad/bin:/nomad"]
      }
    }
  }
}

Start your dev agent

$ nomad agent -dev -config=docker.hcl

Run the example job, connect to the alloc, and verify that your folder mounted

[root@nomad-client-1 ~]# nomad run example.nomad
==> Monitoring evaluation "a876a981"
    Evaluation triggered by job "example"
    Allocation "56c7bfab" created: node "ccb65cd0", group "cache"
    Evaluation within deployment: "1786f73f"
    Evaluation status changed: "pending" -> "complete"
==> Evaluation "a876a981" finished with status "complete"

[root@nomad-client-1 ~]# nomad alloc status 56c
ID                  = 56c7bfab-d99f-15bd-45cf-ba78cc47dd21
Eval ID             = a876a981
Name                = example.cache[0]
Node ID             = ccb65cd0
Node Name           = nomad-client-1.node.consul
Job ID              = example
Job Version         = 0
Client Status       = running
Client Description  = Tasks are running
Desired Status      = run
Desired Description = <none>
Created             = 9s ago
Modified            = 2s ago
Deployment ID       = 1786f73f
Deployment Health   = unset

Task "redis" is "running"
Task Resources
CPU        Memory           Disk     Addresses
0/100 MHz  980 KiB/300 MiB  300 MiB  

Task Events:
Started At     = 2020-10-15T22:55:36Z
Finished At    = N/A
Total Restarts = 0
Last Restart   = N/A

Recent Events:
Time                       Type        Description
2020-10-15T18:55:36-04:00  Started     Task started by client
2020-10-15T18:55:28-04:00  Driver      Downloading image
2020-10-15T18:55:28-04:00  Task Setup  Building Task Directory
2020-10-15T18:55:28-04:00  Received    Task received by client

[root@nomad-client-1 ~]# nomad alloc exec 56c sh
# cd /
# cd nomad
# ls
nomad-v0.10.4							      nomad-v0.11.0-lifecycle	 nomad-v0.12.4
nomad-v0.10.4-spread						      nomad-v0.11.0-spread	 nomad-v0.12.4+ent
nomad-v0.10.5							      nomad-v0.11.3		 nomad-v0.12.4-rc1
nomad-v0.11.0-beta2						      nomad-v0.12.0		 nomad-v0.12.5
nomad-v0.11.0-dev						      nomad-v0.12.0-b1-poststop
nomad-v0.11.0-f-csi-volumes-301437e802273eabc5c72b92f23e4598e030a2ba  nomad-v0.12.3
# exit