Overview

This guide shows how to diagnose and fix the Docker BuildKit error:

failed to solve with frontend dockerfile.v0: failed to create LLB definition

It typically means BuildKit couldn’t parse your Dockerfile, couldn’t build the dependency graph (LLB), or failed early (e.g., auth, missing files, or syntax issues).

Quickstart: Get Clear Logs and Try a Known-Good Build

• Force verbose logs:
  • docker build: DOCKER_BUILDKIT=1 docker build --progress=plain .
  • buildx: docker buildx build --progress=plain .
• Read the first error line above the message—often it names the real cause (e.g., missing file, auth, unknown flag).
• Test a minimal working example below. If it succeeds, your environment is fine and the issue is specific to your Dockerfile or context.

Minimal Working Example (MWE)

Create a tiny project that should build on any recent Docker Engine with BuildKit enabled.

mkdir mwe && cd mwe
cat > Dockerfile <<'EOF'
# syntax=docker/dockerfile:1.7
FROM alpine:3.20
RUN apk add --no-cache curl
COPY hello.sh /usr/local/bin/hello
RUN chmod +x /usr/local/bin/hello
ENTRYPOINT ["hello"]
EOF

cat > hello.sh <<'EOF'
#!/bin/sh
echo "Hello from BuildKit!"
EOF

DOCKER_BUILDKIT=1 docker build -t mwe:ok .
docker run --rm mwe:ok

If this builds and runs, BuildKit and your network are functional. Compare differences to your failing Dockerfile.

Step-by-Step Diagnosis and Fixes

1. Turn on plain progress and inspect the real error

• Run: DOCKER_BUILDKIT=1 docker build --progress=plain .
• Look for lines mentioning: unknown flag, missing file, auth, cannot find stage, unsupported syntax.

1. Add or update the Dockerfile frontend syntax directive

• Put this as the first line when using newer features:

  • syntax=docker/dockerfile:1.7

• Fixes parsing of features like RUN --mount, COPY --link, heredocs, and ARG in FROM.

1. Verify base image pull and registry auth

• Ensure the base image exists: docker pull alpine:3.20 (replace accordingly).
• If private registry: docker login REGISTRY && docker pull REGISTRY/IMAGE:TAG
• If behind a proxy, configure Docker daemon proxy and retry.

1. Check COPY/ADD sources and build context

• Files must exist inside the build context (the directory you pass to docker build).
• Common mistakes:
  • COPY ../something /app ← invalid (outside context)
  • .dockerignore excludes a file you COPY. Review .dockerignore.
• Validate by listing what’s sent to the daemon: run docker build with --no-cache and watch which files are included.

1. Validate ARG usage, especially in FROM

• If you use ARG in FROM, declare it before the first FROM:
  • ARG BASE=alpine:3.20
  • FROM ${BASE}
• Ensure you pass required build args: docker build --build-arg BASE=alpine:3.20 .

1. Fix multi-stage references

• Ensure stage names exist before referencing them:
  • FROM node:20 AS builder
  • ...
  • COPY --from=builder /app/dist /srv
• Typos or missing stages cause LLB graph creation to fail.

1. Remove unsupported flags for your frontend version

• Flags like RUN --mount or COPY --link require a recent frontend (see step 2).
• If you can’t upgrade, remove or gate these features.

1. Refresh the builder and cache

• docker buildx ls
• docker buildx create --use --name fix-builder
• docker builder prune -af
• Retry the build.

1. Update Docker and Buildx

• Ensure Docker Engine, Buildx, and the dockerfile frontend are reasonably current (e.g., Engine ≥ 24.x where possible).

1. Isolate BuildKit vs legacy builder

• If you must bisect: DOCKER_BUILDKIT=0 docker build .
• If legacy works but BuildKit fails, you’re likely using a BuildKit-only feature incorrectly or missing the syntax directive.

Common Symptoms and Targeted Fixes

Practical Fix Patterns

• Start Dockerfile with: # syntax=docker/dockerfile:1.7
• Keep Dockerfile features aligned with your Engine/Buildx version.
• Confirm every COPY source exists inside the build context.
• Log in to private registries before building.
• Use explicit tags for base images.
• Prefer simple, deterministic steps; avoid relying on files generated at build time before they exist.

CI/CD Notes

• Ensure the CI runner has Docker Buildx enabled: docker buildx create --use
• Mirror configuration, proxies, and credentials between local and CI.
• Pin the dockerfile frontend and base image tags to reduce drift.

Pitfalls to Avoid

• Missing syntax directive when using modern instructions (RUN --mount, heredocs, COPY --link).
• .dockerignore excluding files you COPY (e.g., ignoring dist/ then COPY dist/…).
• Referring to paths outside the build context.
• Using ARG in FROM without declaring it first.
• Relying on implicit latest tags for base images that change unexpectedly.

Performance Notes (while fixing)

• Keep BuildKit enabled; it provides parallelism and caching.
• Use .dockerignore to shrink context, but double-check required files aren’t excluded.
• Consider RUN --mount=type=cache for package managers once your syntax directive is set.
• Use multi-stage builds to copy only final artifacts and reduce image size.
• Prune stale caches if builds behave inconsistently: docker builder prune -af

Tiny FAQ

• What is LLB?

  • The Low-Level Build graph created by BuildKit from your Dockerfile. This error means the graph couldn’t be created.

• Why does it work locally but not in CI?

  • Differences in Buildx version, frontend, network/proxy, or missing registry credentials. Align versions and config.

• Can I just disable BuildKit?

  • Temporarily, yes (DOCKER_BUILDKIT=0). Prefer fixing syntax or environment so you keep BuildKit benefits.

• How do I pin the Dockerfile frontend?

  • Add at the first line: # syntax=docker/dockerfile:1.7

• How do I verify the real root cause?

  • Rebuild with --progress=plain and read the first meaningful error line above the LLB message.