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Docker in Workspaces

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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 or Docker host(s) for secure docker-in-docker and systemd-in-docker. Works with GKE, EKS, AKS, Docker.	Requires compatible nodes. Limitations
Envbox	A container image with all the packages necessary to run an inner Sysbox container. Removes the need to setup sysbox-runc on your nodes. Works with GKE, EKS, AKS.	Requires running the outer container as privileged (the inner container that acts as the workspace is locked down). Requires compatible nodes.
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/example-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
    set -e
    sudo service docker start
  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
    set -e
    sudo service docker start
  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/example-base:ubuntu"
      command = ["sh", "-c", coder_agent.main.init_script]
    }
  }
}

Envbox

Envbox is an image developed and maintained by Coder that bundles the sysbox runtime. It works by starting an outer container that manages the various sysbox daemons and spawns an unprivileged inner container that acts as the user's workspace. The inner container is able to run system-level software similar to a regular virtual machine (e.g. systemd, dockerd, etc). Envbox offers the following benefits over running sysbox directly on the nodes:

No custom runtime installation or management on your Kubernetes nodes.
No limit to the number of pods that run envbox.

Some drawbacks include:

The outer container must be run as privileged
- Note: the inner container is not privileged. For more information on the security of sysbox containers see sysbox's official documentation.
Initial workspace startup is slower than running sysbox-runc directly on the nodes. This is due to envbox having to pull the image to its own Docker cache on its initial startup. Once the image is cached in envbox, startup performance is similar.

Envbox requires the same kernel requirements as running sysbox directly on the nodes. Refer to sysbox's compatibility matrix to ensure your nodes are compliant.

To get started with envbox check out the starter template or visit the repo.

Authenticating with a Private Registry

Authenticating with a private container registry can be done by referencing the credentials via the CODER_IMAGE_PULL_SECRET environment variable. It is encouraged to populate this environment variable by using a Kubernetes secret.

Refer to your container registry documentation to understand how to best create this secret.

The following shows a minimal example using a the JSON API key from a GCP service account to pull a private image:

# Create the secret
$ kubectl create secret docker-registry <name> \
  --docker-server=us.gcr.io \
  --docker-username=_json_key \
  --docker-password="$(cat ./json-key-file.yaml)" \
  --docker-email=<service-account-email>

env {
  name = "CODER_IMAGE_PULL_SECRET"
  value_from {
    secret_key_ref {
      name = "<name>"
      key = ".dockerconfigjson"
    }
  }
}

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.

Before using Podman, please review the following 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: - name: fuse-device-plugin-ctr image: soolaugust/fuse-device-plugin:v1.0 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 might need to disable SELinux or set it to permissive mode.
Use this 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

Rootless Podman on Bottlerocket nodes

Rootless containers rely on Linux user-namespaces. Bottlerocket disables them by default (user.max_user_namespaces = 0), so Podman commands will return an error until you raise the limit:

cannot clone: Invalid argument
user namespaces are not enabled in /proc/sys/user/max_user_namespaces

Add a user.max_user_namespaces value to your Bottlerocket user data to use rootless Podman on the node:

[settings.kernel.sysctl]
"user.max_user_namespaces" = "65536"

Reboot the node.
Verify that the value is more than 0:

sysctl -n user.max_user_namespaces

For Karpenter-managed Bottlerocket nodes, add the user.max_user_namespaces setting in your EC2NodeClass:

apiVersion: karpenter.k8s.aws/v1
kind: EC2NodeClass
metadata:
  name: bottlerocket-rootless
spec:
  amiFamily: Bottlerocket # required for BR-style userData
  # …
  userData: |
    [settings.kernel]
    sysctl = { "user.max_user_namespaces" = "65536" }

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/example-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
        run_as_user = 0
      }
      command = ["dockerd", "-H", "tcp://127.0.0.1:2375"]
    }
    container {
      name    = "dev"
      image   = "codercom/example-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.

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"
}

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/example-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
      ]
    }
  }
}