What this snippet does
Copying manifests first keeps the expensive install layer cached when only source files change.
Expected output
=> CACHED [4/6] RUN npm ci
Why practise typing this
Typing layers & caching code builds muscle memory for the symbols and indentation Docker uses most, which prose-based typing tests never cover. DevType measures your words per minute and accuracy on this snippet and tracks the individual characters you mistype, so later lessons can target them.
More Docker practice
- COPY . . invalidates everythingLayers & Caching · intermediate
- Chaining to one layerLayers & Caching · intermediate
- Deleting in a later layerLayers & Caching · intermediate
- BuildKit cache mountLayers & Caching · advanced
- Go module cacheLayers & Caching · advanced
- Inspecting layer sizesLayers & Caching · intermediate