Why size matters and how to reduce it.
WHY SIZE MATTERS
Transfer time on every deployment Storage on every host Startup delay when pulling Attack surface
WHAT MAKES IMAGES LARGE
A full operating system as the base Build tools left in the final image Package manager caches Source code and dependencies not needed at runtime Files deleted in a later layer
WHAT A MULTI-STAGE BUILD DOES
Builds in one stage, then copies only the result into a clean final stage.
WHY THAT IS THE SINGLE BIGGEST IMPROVEMENT
Compilers, headers and development dependencies never reach the final image.
WHAT TO COPY FORWARD
The built artefact and its runtime dependencies only.
WHAT SLIM AND MINIMAL BASE IMAGES PROVIDE
Far smaller images.
WHAT THEY COST
Missing tools, which complicates debugging Occasionally, missing libraries your application needs
WHAT A DISTROLESS IMAGE IS
One containing the runtime and nothing else, not even a shell.
WHAT THAT PROVIDES
A very small attack surface.
WHAT IT COSTS
No shell to debug with.
WHAT TO USE FOR EXCLUSIONS
An ignore file, so unnecessary files never enter the build context.
WHY THAT MATTERS
The whole context is sent to the builder, including anything large or secret.
WHAT TO ALWAYS EXCLUDE
Version control directories, dependency folders, and environment files.
