Answer
Docker caches based on file changes only. External states do not invalidate cache.
Quick Answer
Docker caches layers based on the instruction and its context at build time. RUN commands that download from the internet (apt-get, curl) are cached based on the instruction text — not the external content. So if an apt package updates, Docker still uses the cached layer. To force a fresh download, break the cache manually.
S
SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ