Configure the LXC task driver plugin

The lxc driver provides an interface for using LXC for running application containers. This tutorial walks through the steps involved in configuring a Nomad client agent to be able to run LXC jobs. You can download the external LXC driver here.

Install the LXC task driver plug-in dependencies

Before deploying an LXC workload, you will need to install the lxc and lxc-templates packages which will provide the runtime and templates to start your container. Run the following command:

$ sudo apt install -y lxc lxc-templates

Download and install the LXC task driver plug-in

External drivers must be placed in the plugin_dir directory which defaults to data_dir/plugins.

Make a directory called plugins in data_dir (which is /opt/nomad/data in the example below)

$ sudo mkdir -p /opt/nomad/data/plugins

Download LXC driver.

$ curl -O https://releases.hashicorp.com/nomad-driver-lxc/0.1.0-rc2/nomad-driver-lxc_0.1.0-rc2_linux_amd64.zip

Unzip the binary.

$ unzip nomad-driver-lxc_0.1.0-rc2_linux_amd64.zip
Archive:  nomad-driver-lxc_0.1.0-rc2_linux_amd64.zip
  inflating: nomad-driver-lxc

Move the LXC driver into your new plugins directory.

$ sudo mv nomad-driver-lxc /opt/nomad/data/plugins

You can now delete the original zip file:

$ rm ./nomad-driver-lxc*.zip

Verify the LXC task driver status

After completing the previous steps, you do not need to explicitly enable the LXC driver in the client configuration, as it is enabled by default.

Restart the Nomad client service:

$ sudo systemctl restart nomad

After a few seconds, run the nomad node status command to verify the client node is ready:

$ nomad node status
ID        DC   Name             Class   Drain  Eligibility  Status
81c22a0c  dc1  ip-172-31-5-174  <none>  false  eligible     ready

You can now run the nomad node status command against the specific node ID to enumerate the drivers initialized on the client. In the example case, the client node ID is 81c22a0c—your client node ID will be different. When configured properly, the "Driver Status" line should include "lxc" in the list as shown below:

$ nomad node status 81c22a0c
ID            = 81c22a0c
Name          = ip-172-31-5-174
Class         = <none>
DC            = dc1
Drain         = false
Eligibility   = eligible
Status        = ready
Uptime        = 2h13m30s
Driver Status = docker,exec,java,lxc,mock_driver,raw_exec,rkt
...

Register the Nomad job

You can run this LXC example job to register a Nomad job that deploys an LXC workload.

$ nomad run lxc.nomad
==> Monitoring evaluation "d8be10f4"
    Evaluation triggered by job "example-lxc"
    Allocation "4248c82e" created: node "81c22a0c", group "example"
    Allocation "4248c82e" status changed: "pending" -> "running" (Tasks are running)
    Evaluation status changed: "pending" -> "complete"
==> Evaluation "d8be10f4" finished with status "complete"

Check the status of the job

Run the following command to check the status of the jobs in your cluster:

$ nomad status
ID           Type     Priority  Status   Submit Date
example-lxc  service  50        running  2019-01-28T22:05:36Z

The output above shows the job running successfully. You can obtain detailed information about the specific job with the following command:

$ nomad status example-lxc
ID            = example-lxc
Name          = example-lxc
Submit Date   = 2019-01-28T22:05:36Z
Type          = service
Priority      = 50
Datacenters   = dc1
Status        = running
Periodic      = false
Parameterized = false

Summary
Task Group  Queued  Starting  Running  Failed  Complete  Lost
example     0       0         1        0       0         0

Allocations
ID        Node ID   Task Group  Version  Desired  Status   Created    Modified
4248c82e  81c22a0c  example     0        run      running  6m58s ago  6m47s ago

Explore additional plug-in options

The LXC driver is enabled by default in the client configuration. In order to provide additional options to the LXC plugin, add plugin options volumes_enabled and lxc_path for the lxc driver in the client's configuration file like in the following example:

plugin "nomad-driver-lxc" {
  config {
    enabled = true
    volumes_enabled = true
    lxc_path = "/var/lib/lxc"
  }
}

Next steps

At this point, your clusters will be configured to run LXC jobs on this client. Continue performing this step on all cluster nodes that you would like to be able to run LXC jobs. You will use this same process to enable LXC in your production clusters, allowing you to run even more types of workload in Nomad.

Reference material

• Official LXC documentation
• Nomad LXC external driver documentation
• Nomad LXC external driver repo