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Building Containers from Scratch: Layers
Exploring how OCI images represent layers, how layers can modify and delete files from previous layers, and how container runtimes combine layers into a single filesystem.
Finally, layers are often distributed as gzipped tarballs, with the.tar.gz extension, to save storage space and reduce network data transfer. Actually un-tarring each layer into the rootfs directory sequentially, taking care to apply file modifications or whiteout deletes, for each container launched, would be very slow. While image layers are "just" tar archives containing files, it is possible to extend the format with additional capabilities for more efficient storage and transfer.
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