etcd

Start an etcd image

Run the following command and replace <tag> with the image variant you want to run

docker run \
  -p 2379:2379 \
  -p 2380:2380 \
  --name etcd registry.ghost-prod.alphabravo.io/ghost-base/etcd:<tag> \
  /usr/local/bin/etcd \
  --name node1

Common etcd use cases

Single-node development instance

Start a simple etcd instance for local development and testing.

docker run -d \
  --name etcd-standalone \
  -p 2379:2379 \
  -p 2380:2380 \
  registry.ghost-prod.alphabravo.io/ghost-base/etcd:<tag> \
  /usr/local/bin/etcd \
  --name node1 \
  --listen-client-urls http://0.0.0.0:2379 \
  --advertise-client-urls http://localhost:2379 \
  --listen-peer-urls http://0.0.0.0:2380 \
  --initial-advertise-peer-urls http://localhost:2380

Multi-node cluster with Docker Compose

Deploy an etcd cluster with multiple nodes for high availability. (Not intended for production as gRPC and http server run on a single port)

x-common-etcd: &etcd-svc
  image: registry.ghost-prod.alphabravo.io/ghost-base/etcd:<tag>
  entrypoint: ["/usr/local/bin/etcd"]
  command:
    - --data-dir=/etcd-data
    - --listen-client-urls=http://0.0.0.0:2379
    - --listen-peer-urls=http://0.0.0.0:2380
    - --initial-cluster=etcd1=http://etcd1:2380,etcd2=http://etcd2:2380,etcd3=http://etcd3:2380
    - --initial-cluster-token=etcd-cluster
    - --initial-cluster-state=new
    - --log-level=warn
  restart: unless-stopped
  networks: [etcd-net]

services:
  etcd1:
    <<: *etcd-svc
    hostname: etcd1
    container_name: etcd1
    environment:
      ETCD_NAME: etcd1
      ETCD_INITIAL_ADVERTISE_PEER_URLS: http://etcd1:2380
      ETCD_ADVERTISE_CLIENT_URLS: http://etcd1:2379
    ports: ["2379:2379"]  # expose one client port to host

  etcd2:
    <<: *etcd-svc
    hostname: etcd2
    container_name: etcd2
    environment:
      ETCD_NAME: etcd2
      ETCD_INITIAL_ADVERTISE_PEER_URLS: http://etcd2:2380
      ETCD_ADVERTISE_CLIENT_URLS: http://etcd2:2379

  etcd3:
    <<: *etcd-svc
    hostname: etcd3
    container_name: etcd3
    environment:
      ETCD_NAME: etcd3
      ETCD_INITIAL_ADVERTISE_PEER_URLS: http://etcd3:2380
      ETCD_ADVERTISE_CLIENT_URLS: http://etcd3:2379

networks:
  etcd-net: {}

Using etcdctl for cluster management

Connect to your etcd cluster and perform administrative operations.

Check cluster health:

docker run --rm -it --network host \
  registry.ghost-prod.alphabravo.io/ghost-base/etcd:<tag>-dev \
  etcdctl --endpoints=localhost:2379 endpoint health

Put and get key-value pairs:

docker run --rm -it --network host \
  registry.ghost-prod.alphabravo.io/ghost-base/etcd:<tag>-dev \
  etcdctl --endpoints=localhost:2379 put mykey "Hello etcd"

docker run --rm -it --network host \
  registry.ghost-prod.alphabravo.io/ghost-base/etcd:<tag>-dev \
  etcdctl --endpoints=localhost:2379 get mykey

Create a snapshot for backup:

docker run --rm -it -v $(pwd):/backup --network host \
  registry.ghost-prod.alphabravo.io/ghost-base/etcd:<tag>-dev \
  etcdctl --endpoints=localhost:2379 snapshot save /backup/snapshot.db

Persistent storage for production

Configure etcd with persistent volumes to maintain data across container restarts.

docker run -d \
  --name etcd-persistent \
  -p 2379:2379 \
  -p 2380:2380 \
  -v etcd-data:/etcd-data \
  registry.ghost-prod.alphabravo.io/ghost-base/etcd:<tag> \
  /usr/local/bin/etcd \
  --name node1 \
  --data-dir=/etcd-data \
  --listen-client-urls http://0.0.0.0:2379 \
  --advertise-client-urls http://localhost:2379

Non-hardened images vs. Ghost hardened images

Key differences

Why no shell or package manager?

Ghost hardened images prioritize security through minimalism:

• Reduced attack surface: Fewer binaries mean fewer potential vulnerabilities
• Immutable infrastructure: Runtime containers shouldn't be modified after deployment
• Compliance ready: Meets strict security requirements for regulated environments

The hardened images intended for runtime don't contain a shell nor any tools for debugging. Common debugging methods for applications built with Ghost hardened images include:

• Docker Debug to attach to containers
• Docker's Image Mount feature to mount debugging tools
• Ecosystem-specific debugging approaches

Docker Debug provides a shell, common debugging tools, and lets you install other tools in an ephemeral, writable layer that only exists during the debugging session.

For example, you can use Docker Debug:

docker debug registry.ghost-prod.alphabravo.io/ghost-base/etcd:<tag>

or mount debugging tools with the Image Mount feature:

docker run --rm -it --pid container:my-etcd \
  --mount=type=image,source=registry.ghost-prod.alphabravo.io/ghost-base/busybox,destination=/dbg,ro \
  registry.ghost-prod.alphabravo.io/ghost-base/etcd:<tag> /dbg/bin/sh

Image variants

Ghost hardened images come in different variants depending on their intended use.

Runtime variants are designed to run your application in production. These images are intended to be used either directly or as the FROM image in the final stage of a multi-stage build. These images typically:

• Run as the nonroot user
• Do not include a shell or a package manager
• Contain only the minimal set of libraries needed to run the app

Build-time variants typically include dev in the variant name and are intended for use in the first stage of a multi-stage Dockerfile. These images typically:

• Run as the root user
• Include a shell and package manager
• Are used to build or compile applications

Migrate to a Ghost hardened image

To migrate your application to a Ghost hardened image, you must update your Dockerfile. At minimum, you must update the base image in your existing Dockerfile to a Ghost hardened image. This and a few other common changes are listed in the following table of migration notes:

The following steps outline the general migration process.

1. Find hardened images for your app. A hardened image may have several variants. Inspect the image tags and find the image variant that meets your needs.
2. Update the base image in your Dockerfile. Update the base image in your application's Dockerfile to the hardened image you found in the previous step. For framework images, this is typically going to be an image tagged as dev because it has the tools needed to install packages and dependencies.
3. For multi-stage Dockerfiles, update the runtime image in your Dockerfile. To ensure that your final image is as minimal as possible, you should use a multi-stage build. All stages in your Dockerfile should use a hardened image. While intermediary stages will typically use images tagged as dev, your final runtime stage should use a non-dev image variant.
4. Install additional packages Ghost hardened images contain minimal packages in order to reduce the potential attack surface. You may need to install additional packages in your Dockerfile. Inspect the image variants to identify which packages are already installed. Only images tagged as dev typically have package managers. You should use a multi-stage Dockerfile to install the packages. Install the packages in the build stage that uses a dev image. Then, if needed, copy any necessary artifacts to the runtime stage that uses a non-dev image. For Alpine-based images, you can use apk to install packages. For Debian-based images, you can use apt-get to install packages.

Troubleshoot migration

General debugging

The hardened images intended for runtime don't contain a shell nor any tools for debugging. The recommended method for debugging applications built with Ghost hardened images is to use Docker Debug to attach to these containers. Docker Debug provides a shell, common debugging tools, and lets you install other tools in an ephemeral, writable layer that only exists during the debugging session.

Permissions

By default image variants intended for runtime, run as the nonroot user. Ensure that necessary files and directories are accessible to the nonroot user. You may need to copy files to different directories or change permissions so your application running as the nonroot user can access them.

Privileged ports

Non-dev hardened images run as a nonroot user by default. As a result, applications in these images can't bind to privileged ports (below 1024) when running in Kubernetes or in Docker Engine versions older than 20.10.

No shell

By default, image variants intended for runtime don't contain a shell. Use dev images in build stages to run shell commands and then copy any necessary artifacts into the runtime stage. In addition, use Docker Debug to debug containers with no shell.

Entry point

Ghost hardened images may have different entry points than images such as Docker Official Images. Use docker inspect to inspect entry points for Ghost hardened images and update your Dockerfile if necessary.