Answer
It avoids duplicating data. If many containers use the same layer, Docker creates a new copy only when modification occurs—saving disk space.
Quick Answer
Copy-on-write means containers share read-only image layers until they need to modify a file. When a container writes to a file from an image layer, Docker copies that file into the container's writable layer first — then modifies the copy. The original image layer stays unchanged, shared by all containers.
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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