Cut Your Docker Build Time in Half: 6 Essential Optimization Techniques

"Docker builds images in layers, caching each one.When you rebuild, Docker reuses unchanged layers to avoid re-executing steps - this is build caching. So the order of your instructions and the size of your build context have huge impact on speed and image size. Here are the quick tips to optimize and achieve 2 times faster speed building images:"

"Every instruction ( FROM, RUN, COPY, etc.) creates a new layer.When one layer changes, all layers after it are rebuilt.So to maximize cache reuse, put the least frequently changing instructions (e.g., installing OS packages) near the top, and the most frequently changing (like copying your source code) at the bottom. Example: Bad Dockerfile: When you change any source file, the entire build re-runs from COPY . ., which invalidates cache for npm install."

Docker builds images in layers and caches each layer so rebuilt images reuse unchanged layers and avoid re-running steps. The order of Dockerfile instructions and the size of the build context strongly affect build speed and final image size. Each Dockerfile instruction (FROM, RUN, COPY, etc.) creates a new layer. When one layer changes, all subsequent layers are rebuilt, invalidating cache. To maximize cache reuse, place least-frequently changing steps, like OS package installation, near the top and place frequent changes, such as copying source code, near the bottom. Reducing build context and ordering instructions can roughly double build speed.

Read at Medium