Caching

Image Layers

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Image History

We can look for the image history by,

docker image history nginx

This should output the nginx image history.

We get a list of image layers. All the images start from a scratch. Each layer contains the increment of the previous one. It could be changes in file system or adding some config/metadata to the image.

We can have on layer, we can even have thousands of layers.

Figure Image Layers

We never store the same image layer twice in the system.

Figure Copy On Write

Image Inspection

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We can closely inspect the image,

docker image inspect nginx

Image inspections give us metadata, some interesting config we can look for,

exposed ports

env variables

start up command