# Docker in Docker

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

| Method                                                     | Description                                                                                                                              | Limitations                                                                                                                                                                                                 |
| ---------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [Sysbox container runtime](#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](https://github.com/nestybox/sysbox#host-requirements). Max of 16 sysbox pods per node. [See all](https://github.com/nestybox/sysbox/blob/master/docs/user-guide/limitations.md) |
| [Rootless Podman](#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](https://github.com/containers/podman/blob/main/rootless.md#shortcomings-of-rootless-podman)                                                      |
| [Privileged docker sidecar](#privileged-sidecar-container) | 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](https://github.com/nestybox/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](https://github.com/nestybox/sysbox/blob/master/docs/distro-compat.md) to implement these security features. Sysbox can also be used to run systemd inside Coder workspaces. See [Systemd in Docker](#systemd-in-docker).

### Use Sysbox in Docker-based templates

After [installing Sysbox](https://github.com/nestybox/sysbox#installation) on the Coder host, modify your template to use the sysbox-runc runtime:

```hcl
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](https://github.com/nestybox/sysbox/blob/master/docs/user-guide/install-k8s.md), modify your template to use the sysbox-runc RuntimeClass. This requires the Kubernetes Terraform provider version 2.16.0 or greater.

```hcl
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](https://github.com/nestybox/sysbox/blob/master/docs/user-guide/install-k8s.md#limitations) for more details.

## Rootless podman

[Podman](https://docs.podman.io/en/latest/) 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:

- [Basic setup and use of Podman in a rootless environment](https://github.com/containers/podman/blob/main/docs/tutorials/rootless_tutorial.md)

- [Shortcomings of Rootless Podman](https://github.com/containers/podman/blob/main/rootless.md#shortcomings-of-rootless-podman)

1. Enable [smart-device-manager](https://gitlab.com/arm-research/smarter/smarter-device-manager#enabling-access) to securely expose a FUSE devices to pods.

   ```sh
     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
   ```

2. Be sure to label your nodes to enable smarter-device-manager:

   ```sh
   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.

3. For systems running SELinux (typically Fedora-, CentOS-, and Red Hat-based systems), you may need to disable SELinux or set it to permissive mode.

4. Import our [kubernetes-podman](https://github.com/coder/coder/tree/main/examples/templates/kubernetes-podman) example template, or make your own.

   ```sh
   echo "kubernetes-podman" | coder templates init
   cd ./kubernetes-podman
   coder templates create
   ```

   > For more information around the requirements of rootless podman pods, see: [How to run Podman inside of Kubernetes](https://www.redhat.com/sysadmin/podman-inside-kubernetes)

## Privileged sidecar container

A [privileged container](https://docs.docker.com/engine/reference/run/#runtime-privilege-and-linux-capabilities) 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

```hcl
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

```hcl
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](https://github.com/nestybox/sysbox) can be used to give workspaces full `systemd` capabilities.

After [installing Sysbox on Kubernetes](https://github.com/nestybox/sysbox/blob/master/docs/user-guide/install-k8s.md),
modify your template to use the sysbox-runc RuntimeClass. This requires the Kubernetes Terraform provider version 2.16.0 or greater.

```hcl
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"
}

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 {

    # Use Sysbox container runtime (required)
    runtime_class_name = "sysbox-runc"

    # Run as root in order to start systemd (required)
    security_context {
      run_as_user = 0
      fs_group    = 0
    }

    container {
      name = "dev"
      env {
        name  = "CODER_AGENT_TOKEN"
        value = coder_agent.main.token
      }
      image = "codercom/enterprise-base:ubuntu"
      command = ["sh", "-c", <<EOF
    # Start the Coder agent as the "coder" user
    # once systemd has started up
    sudo -u coder --preserve-env=CODER_AGENT_TOKEN /bin/bash -- <<-'    EOT' &
    while [[ ! $(systemctl is-system-running) =~ ^(running|degraded) ]]
    do
      echo "Waiting for system to start... $(systemctl is-system-running)"
      sleep 2
    done
    ${coder_agent.main.init_script}
    EOT

    exec /sbin/init
    EOF
      ]
    }
  }
}
```