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docker-knowledge-patch

Deployment & operations

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Updated 10-16 01:35

About this skill

Docker Knowledge Patch

Baseline: Docker Engine 24.x and Compose 2.x. Covered range: Engine 25.0.0 through 29.3, Engine API v1.44 through v1.55, Compose 5.0.0 through 5.3.0, Buildx 0.30.0 through 0.35.0, BuildKit 0.28.0, and Dockerfile 1.22.0.

Included versioned batches: 25.0.0, 26.0.0, 27.0.1, 28.0.0, 0.30.0, 5.0.0, 0.31.0, 5.1.0, 0.28.0, 1.22.0, 0.32.0, 0.33.0, 0.34.0, 0.35.0, 5.2.0, and 5.3.0.

Use this patch

  1. Identify whether the task targets Engine runtime, networking, images, the Engine API, Go integration, Buildx, BuildKit/Dockerfile, or Compose.
  2. Read the matching reference before changing configuration, client calls, parsers, or automation.
  3. Check both the daemon version and negotiated API version; several defaults and response shapes are API-gated.
  4. Treat fresh installations, upgrades, and downgrades separately. Engine 28 and 29 include stateful storage and firewall transitions.
  5. Make output parsing explicit. Several human-oriented CLI defaults changed, while event and Compose JSON streams use record framing.

Reference index

Reference Topics
runtime.md Daemon startup and reload, storage, mounts, resources, security, rootless, Windows, Swarm, platform support
networking.md Attachments, DNS, IPv4/IPv6, IPAM, gateway modes, firewall backends, routing
images-registry.md Image store, archives, platform selection, manifests, formats, registry behavior, provenance
engine-api.md API compatibility, schema changes, event framing, inspection, updates, deprecations
go-sdk-cli.md Go modules and client migrations, removed APIs, CLI behavior and embedding
buildx.md Bake, exporters, Imagetools, source policies, builders, provenance, resources
buildkit-dockerfile.md BuildKit sources and verification, provenance, deployment, Dockerfile frontend and linting
compose.md Compose 5 migration, builds, lifecycle, providers, publish, watch, output, init containers

Breaking changes and migration priorities

Engine 29 fresh installations

  • Fresh Engine 29 installations use the containerd image store by default; upgrades keep their existing store. userns-remap temporarily prevents use of the containerd store.
  • Bundled containerd 2.1.5 follows systemd's LimitNOFILE, changing the container default from 1048576 to 1024. Set --ulimit or default-ulimits for workloads that require more descriptors.
{
  "default-ulimits": {
    "nofile": { "Name": "nofile", "Soft": 1048576, "Hard": 1048576 }
  }
}
  • Do not assume the old image-list table: docker image ls now uses a collapsed tree and hides untagged images unless --all is set. Give scripts an explicit --format.
  • Legacy-link environment variables are no longer injected by default. DOCKER_KEEP_DEPRECATED_LEGACY_LINKS_ENV_VARS=1 is only a temporary compatibility switch.

Firewall and network transitions

  • Engine 28.0.0 requires kernel ipset support and installs redesigned iptables/ip6tables rules. Before downgrading, remove those rules; rebooting is the simplest documented cleanup.
  • Engine 28.0.0 blocks remote direct routing to unpublished ports and prevents neighboring hosts from reaching ports published to host loopback. Publish required ports or deliberately choose a nat-unprotected gateway mode.
  • Engine 29 removes the DOCKER-ISOLATION-STAGE-1 and DOCKER-ISOLATION-STAGE-2 chains. Without the userland proxy, cross-network reachability through host-published ports and nat-unprotected networks can increase.
  • The nftables backend is experimental. Docker does not enable host forwarding in this mode; configure forwarding and non-Docker interface policy yourself.
  • IPv6 ip6tables filtering became stable and default-enabled in 27.0.1. A host that enables IPv6 forwarding independently owns its FORWARD policy.

API compatibility and response parsing

  • Engine 25.0.0 API v1.44 removes image VirtualSize; Engine 26.0.0 removes API versions below v1.24 and image Container/ContainerConfig fields.
  • Engine 29.0 through 29.2 require daemon API v1.44 or newer; 29.3 lowers the raw daemon floor to v1.40. The v29 CLI and Go client still do not negotiate below v1.44.
  • API v1.52 removes many top-level container network fields, omits unset image fields, and can omit GraphDriver with the containerd backend. Read per-network data from NetworkSettings.Networks and tolerate absent optional fields.
  • API v1.53 removes the legacy /system/df arrays in favor of usage summaries and deprecates /grpc and /session.
  • API v1.55 adds image attestations and makes per-device block-I/O update fields live. Distinguish omitted or null update fields from empty arrays, which clear rules.
  • Negotiate event framing explicitly: NDJSON is declared in v1.52, RFC 7464 application/json-seq is accepted in v1.52, and application/jsonl is accepted in v1.53.

Image and registry removals

  • Engine 28.2 cannot pull or push Docker Image v1 or manifest v2 schema 1. Republish content as OCI or manifest v2 schema 2.
  • Engine 28.2 also removes pull-by-tag fallback after digest resolution. Registries must conform to the OCI Distribution Specification.
  • Engine 27 and later reject a non-local remote TCP listener configured with explicit --tls=false or --tlsverify=false. Use verified TLS, a Unix socket, or SSH.
  • Engine 29 removes Docker Content Trust commands and classic-builder DCT support from the CLI; install the trust command separately as a CLI plugin when needed.

Go SDK and CLI integration

  • Stop importing github.com/docker/docker. Use github.com/moby/moby/client and github.com/moby/moby/api; the parent github.com/moby/moby module is internal, release tags use docker-v29.0.0 form, and the SDK requires Go 1.24 or newer.
  • Replace removed NewClient and NewEnvClient; replace ImageCreate with ImagePull or ImageImport.
  • Expect option structs and dedicated result structs instead of positional parameters and raw returns. ContainerExec... methods become Exec..., while pull/push results expose JSONMessages iterators.
  • Migrate IP/subnet values to netip.Addr and netip.Prefix, MAC values to byte slices compatible with net.HardwareAddr, and container Port to PortSummary.
  • Docker CLI embedding lost most exported stock-command constructors and many formatter and Run... helpers. Build on the supported client modules or provide a separate command layer.

Compose 5 migration

  • Compose intentionally jumps from v2 to v5; v3 and v4 were skipped to avoid confusion with obsolete Compose file format labels.
  • Compose 5 removes its internal BuildKit builder and delegates builds to Bake. Remove dependencies on the former internal builder path.
  • Compose 5.2.0 introduces a new state-reconciliation algorithm. Regression-test upgrade convergence for existing projects.
  • docker compose ps --format json emits JSON Lines, not one JSON array. Consume each line as a separate JSON value.
  • Compose 5.3.0 supports native pre-start init containers.

High-use Engine features

Mount image content

Use type=image (since 28.0.0) and optionally select an internal path with image-subpath:

docker run --mount type=image,source=alpine:latest,target=/mnt,image-subpath=etc alpine:latest

Use bind-create-src when a missing bind source should be created. Replace removed bind-nonrecursive with bind-recursive=disabled:

docker run --mount type=bind,src=/host/data,dst=/data,bind-recursive=disabled IMAGE

Anonymous volumes may now be read-only without naming a source.

Select image platforms

  • With the containerd image store, docker image push --platform selects one manifest (since 27.0.1).
  • docker load, docker save, and docker history gained one-platform selection in 28.0.0.
  • Engine 29 accepts comma-separated platform lists for load and save; the API accepts repeated platform parameters.
docker image save --platform linux/amd64,linux/arm64 -o app.tar app:tag

Control network gateways and address families

Choose the default gateway with extended --network syntax and gw-priority:

docker run --network=name=frontend --network=name=egress,gw-priority=100 IMAGE

Use gateway_mode_ipv4 or gateway_mode_ipv6 values nat, routed, nat-unprotected, or, for an internal network, isolated. Create IPv6-only networks with --ipv6 --ipv4=false where supported.

docker network create --ipv6 --ipv4=false v6-only

Configure per-endpoint interface sysctls with the IFNAME placeholder; API v1.48 no longer migrates container-wide eth0 sysctls automatically.

High-use build features

Enforce source policy

  • Buildx 0.31.0 introduces Rego source policy for local contexts; 0.32.0 extends it to Git and HTTP sources and adds Sigstore/provenance inputs.
  • Buildx 0.33.0 adds PGP verification and makes the DAP debugger generally available.
  • Buildx 0.34.0 adds opt-in BUILDX_DEFAULT_POLICY verification for Docker pipeline images and global bake --policy options.
  • Buildx 0.35.0 can proxy build-step network traffic into policy evaluation with BuildKit 0.31.0 or later.
docker buildx build --policy ./policy.rego .
docker buildx bake --policy ./policy.rego

Make outputs and resources deterministic

  • Use local exporter mode=delete to replace rather than merge the destination. Outside the working directory, allow buildx.local.delete explicitly.
  • Use buildx build --resource or Bake's resource key for CPU and memory limits; this requires BuildKit 0.31.0 or later and Dockerfile v1.25.0 or later.
  • Use imagetools create --metadata-file to capture the created descriptor and digest.
  • Use Buildx command --timeout where offered to bound waits for remote builders.

High-use Compose features

  • Use build.no_cache_filter to bypass cache only for named build stages.
  • Use docker compose start --wait to wait for services after starting them.
  • Expect lifecycle hooks on restart, post_start hooks for compose run, and provider stop hooks during shutdown.
  • Compose recreates a container when an image-mounted digest changes.
  • OCI and Git remote resources are supported, including overrides for OCI projects and corrected Windows/SSH path handling.
  • docker compose publish honors optional missing environment files and checks literal inline environment values for sensitive data.
  • Compose Watch no longer rebuilds depends_on services solely because of that relationship.

Preflight checklist

  • Run dockerd --validate --config-file ... to validate configuration and host requirements.
  • Verify the active image store and firewall backend with docker info.
  • Pin or inspect the Engine API version before relying on fields or omission behavior.
  • Make CLI and stream output formats explicit in automation.
  • Test firewall reachability after Engine 28/29 upgrades and before any downgrade.
  • Test Compose convergence after moving to 5.2.0 or later.
  • Read the complete topic reference before changing SDK integrations or compatibility paths.