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Docker in Docker

There are a few ways to run Docker within container-based Coder workspaces.

Method	Description	Limitations
Sysbox container runtime	Install the sysbox runtime on your Kubernetes nodes for secure docker-in-docker and systemd-in-docker. Works with GKE, EKS, AKS.	Requires compatible nodes. Max of 16 sysbox pods per node. See all
Rootless Podman	Run podman inside Coder workspaces. Does not require a custom runtime or privileged containers. Works with GKE, EKS, AKS, RKE, OpenShift	Requires smarter-device-manager for FUSE mounts. See all
Privileged docker sidecar	Run docker as a privileged sidecar container.	Requires a privileged container. Workspaces can break out to root on the host machine.

Sysbox container runtime

The Sysbox container runtime allows unprivileged users to run system-level applications, such as Docker, securely from the workspace containers. Sysbox requires a compatible Linux distribution to implement these security features. Sysbox can also be used to run systemd inside Coder workspaces. See Systemd in Docker.

Use Sysbox in Docker-based templates

After installing Sysbox on the Coder host, modify your template to use the sysbox-runc runtime:

resource "docker_container" "workspace" {
  # ...
  name    = "coder-${data.coder_workspace.me.owner}-${lower(data.coder_workspace.me.name)}"
  image   = "codercom/enterprise-base:ubuntu"
  env     = ["CODER_AGENT_TOKEN=${coder_agent.main.token}"]
  command = ["sh", "-c", coder_agent.main.init_script]
  # Use the Sysbox container runtime (required)
  runtime = "sysbox-runc"
}

resource "coder_agent" "main" {
  arch           = data.coder_provisioner.me.arch
  os             = "linux"
  startup_script = <<EOF
    #!/bin/sh

    # Start Docker
    sudo dockerd &

    # ...
    EOF
}

Use Sysbox in Kubernetes-based templates

After installing Sysbox on Kubernetes, modify your template to use the sysbox-runc RuntimeClass. This requires the Kubernetes Terraform provider version 2.16.0 or greater.

terraform {
  required_providers {
    coder = {
      source  = "coder/coder"
    }
    kubernetes = {
      source = "hashicorp/kubernetes"
      version = "2.16.0"
    }
  }
}

variable "workspaces_namespace" {
  default = "coder-namespace"
}

data "coder_workspace" "me" {}

resource "coder_agent" "main" {
  os   = "linux"
  arch = "amd64"
  dir  = "/home/coder"
  startup_script = <<EOF
    #!/bin/sh

    # Start Docker
    sudo dockerd &

    # ...
  EOF
}

resource "kubernetes_pod" "dev" {
  count = data.coder_workspace.me.start_count
  metadata {
    name      = "coder-${data.coder_workspace.me.owner}-${data.coder_workspace.me.name}"
    namespace = var.workspaces_namespace
    annotations = {
      "io.kubernetes.cri-o.userns-mode" = "auto:size=65536"
    }
  }

  spec {
  runtime_class_name = "sysbox-runc"
  # Use the Sysbox container runtime (required)
    security_context {
      run_as_user = 1000
      fs_group    = 1000
    }
    container {
      name = "dev"
      env {
        name  = "CODER_AGENT_TOKEN"
        value = coder_agent.main.token
      }
      image = "codercom/enterprise-base:ubuntu"
      command = ["sh", "-c", coder_agent.main.init_script]
    }
  }
}

Sysbox CE (Community Edition) supports a maximum of 16 pods (workspaces) per node on Kubernetes. See the Sysbox documentation for more details.

Rootless podman

Podman is Docker alternative that is compatible with OCI containers specification. which can run rootless inside Kubernetes pods. No custom RuntimeClass is required.

Prior to completing the steps below, please review the following Podman documentation:

Enable smart-device-manager to securely expose a FUSE devices to pods.

  cat <<EOF | kubectl create -f -
  apiVersion: apps/v1
  kind: DaemonSet
  metadata:
  name: fuse-device-plugin-daemonset
  namespace: kube-system
  spec:
  selector:
  matchLabels:
      name: fuse-device-plugin-ds
  template:
  metadata:
      labels:
      name: fuse-device-plugin-ds
  spec:
      hostNetwork: true
      containers:
      - image: soolaugust/fuse-device-plugin:v1.0
      name: fuse-device-plugin-ctr
      securityContext:
          allowPrivilegeEscalation: false
          capabilities:
          drop: ["ALL"]
      volumeMounts:
          - name: device-plugin
          mountPath: /var/lib/kubelet/device-plugins
      volumes:
      - name: device-plugin
          hostPath:
          path: /var/lib/kubelet/device-plugins
      imagePullSecrets:
      - name: registry-secret
  EOF

Be sure to label your nodes to enable smarter-device-manager:
```
kubectl get nodes
kubectl label nodes --all smarter-device-manager=enabled
```
⚠️ Warning: If you are using a managed Kubernetes distribution (e.g. AKS, EKS, GKE), be sure to set node labels via your cloud provider. Otherwise, your nodes may drop the labels and break podman functionality.
For systems running SELinux (typically Fedora-, CentOS-, and Red Hat-based systems), you may need to disable SELinux or set it to permissive mode.
Import our kubernetes-with-podman example template, or make your own.
```
echo "kubernetes-with-podman" | coder templates init
cd ./kubernetes-with-podman
coder templates create
```
For more information around the requirements of rootless podman pods, see: How to run Podman inside of Kubernetes

Privileged sidecar container

A privileged container can be added to your templates to add docker support. This may come in handy if your nodes cannot run Sysbox.

⚠️ Warning: This is insecure. Workspaces will be able to gain root access to the host machine.

Use a privileged sidecar container in Docker-based templates

resource "coder_agent" "main" {
  os             = "linux"
  arch           = "amd64"
}

resource "docker_network" "private_network" {
  name = "network-${data.coder_workspace.me.id}"
}

resource "docker_container" "dind" {
  image      = "docker:dind"
  privileged = true
  name       = "dind-${data.coder_workspace.me.id}"
  entrypoint = ["dockerd", "-H", "tcp://0.0.0.0:2375"]
  networks_advanced {
    name = docker_network.private_network.name
  }
}

resource "docker_container" "workspace" {
  count   = data.coder_workspace.me.start_count
  image   = "codercom/enterprise-base:ubuntu"
  name    = "dev-${data.coder_workspace.me.id}"
  command = ["sh", "-c", coder_agent.main.init_script]
  env = [
    "CODER_AGENT_TOKEN=${coder_agent.main.token}",
    "DOCKER_HOST=${docker_container.dind.name}:2375"
  ]
  networks_advanced {
    name = docker_network.private_network.name
  }
}

Use a privileged sidecar container in Kubernetes-based templates

terraform {
  required_providers {
    coder = {
      source  = "coder/coder"
    }
    kubernetes = {
      source = "hashicorp/kubernetes"
      version = "2.16.0"
    }
  }
}

variable "workspaces_namespace" {
  default = "coder-namespace"
}

data "coder_workspace" "me" {}

resource "coder_agent" "main" {
  os             = "linux"
  arch           = "amd64"
}

resource "kubernetes_pod" "main" {
  count = data.coder_workspace.me.start_count
  metadata {
    name      = "coder-${data.coder_workspace.me.owner}-${data.coder_workspace.me.name}"
    namespace = var.namespace
  }
  spec {
    # Run a privileged dind (Docker in Docker) container
    container {
      name  = "docker-sidecar"
      image = "docker:dind"
      security_context {
        privileged = true
      }
      command = ["dockerd", "-H", "tcp://127.0.0.1:2375"]
    }
    container {
      name    = "dev"
      image   = "codercom/enterprise-base:ubuntu"
      command = ["sh", "-c", coder_agent.main.init_script]
      security_context {
        run_as_user = "1000"
      }
      env {
        name  = "CODER_AGENT_TOKEN"
        value = coder_agent.main.token
      }
      # Use the Docker daemon in the "docker-sidecar" container
      env {
        name  = "DOCKER_HOST"
        value = "localhost:2375"
      }
    }
  }
}

Systemd in Docker

Additionally, Sysbox can be used to give workspaces full systemd capabilities.