Troubleshoot Docker build failures

Topic: Containers core

When docker build fails check the failing step, cache, and context. Use --no-cache to rule out cache. Check Dockerfile syntax and paths. Use when a build fails or is slow.

Intent: Troubleshooting

Quick answer

  • Read the error line. Often COPY or RUN path is wrong. Fix path or add file to context. Use .dockerignore to exclude unneeded files.
  • Run with --no-cache to avoid stale cache. Check base image exists and network for apt or pip.
  • Build in stages; run the failing RUN in a temporary container to debug. Check multi-stage COPY --from= paths.

Prerequisites

Steps

  1. Locate failure

    Note which step fails. Check that files exist in build context and paths in COPY and RUN are correct.

  2. Cache and network

    Try docker build --no-cache. For RUN apt or pip ensure network and base image are valid.

  3. Debug step

    Comment out later steps; build to failing step. Run a shell in that layer to reproduce (docker run -it image_id /bin/sh).

Summary

Find failing step; fix paths and context; use —no-cache if needed; debug by running shell at that layer.

Prerequisites

Steps

Step 1: Locate failure

Identify step; verify paths and context.

Step 2: Cache and network

Try —no-cache; check base image and network.

Step 3: Debug step

Build to failure; run shell at that layer to debug.

Verification

  • Build completes; or you know exact fix needed.

Troubleshooting

COPY failed — File not in context or path wrong. RUN failed — Reproduce in interactive container.

Next steps

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