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When the image is pushed to Docker registery, the content of each image layer is compressed and then the corresponding digest(SHA-256) is placed in manifest file.

Manifest file for redis repository has below entries:

        "GraphDriver": {
            "Data": {
                "LowerDir": "/var/lib/docker/overlay2/bd512eb256c8aa56cbe9243d440a311820712d1a245fe6f523d39d19cd6c862d/diff:/var/lib/docker/overlay2/7fa1e90f35c78fc83c3a
4b86e36e45d742383b394adf9ce4cf9b339d919c9cbe/diff:/var/lib/docker/overlay2/2c1869386b5b8542959da4f0173a5272b9703326d619f27258b4edff7a1dbbf9/diff:/var/lib/docker/overlay2
/23ba3955c5b72ec17b9c409bd5233a3d92cbd75543c7d144b364f8188765788e/diff:/var/lib/docker/overlay2/87d8a92919103e8ff723221200acb36e17c611fa499571ab183d0f51458e6f24/diff",
                "MergedDir": "/var/lib/docker/overlay2/e503ed41978e99fe9b71a4225763a40b7988e9a4f31d4c06ef1ec1af46b0b6ab/merged",
                "UpperDir": "/var/lib/docker/overlay2/e503ed41978e99fe9b71a4225763a40b7988e9a4f31d4c06ef1ec1af46b0b6ab/diff",
                "WorkDir": "/var/lib/docker/overlay2/e503ed41978e99fe9b71a4225763a40b7988e9a4f31d4c06ef1ec1af46b0b6ab/work"
            },
            "Name": "overlay2"
        },
        "RootFS": {
            "Type": "layers",
            "Layers": [
                "sha256:6270adb5794c6987109e54af00ab456977c5d5cc6f1bc52c1ce58d32ec0f15f4",
                "sha256:f99f83132c0a553c6444af96c9f8b905bf1e12835f4f1fa1aa67e9b39b461b1b",
                "sha256:03eafa7928765518eb3d5f2bd2bd97dac655833dd088db9e7590eadbb721aa72",
                "sha256:dc5ef0c854b450e002c49b8d3dad8a70b7d70a695f59104d6dea0bb87582baa2",
                "sha256:4c8e44b308d0a525ccda8da176d6daaa6c117c87148ae85396a8171e6996f9f4",
                "sha256:76c5d4259e40d4282ba496be18926dcef62063f99eb463ed2d802dd9a0e303a0"
            ]
        },

This is a 6 layer image.

GraphDriver.Data.LowerDir is referring to non-compressed content hash(digest) of each layer stored in local registry(/var/lib/docker/overlay2)

What digest does RootFS refers to? is it the digest for compressed content(in dockerhub registry) of each image layer?


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