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Last active July 6, 2022 12:55
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BuildKit Survey

experiment 1

  1. Create a simple Dockerfile to build an apline image.
  2. Use build and buildx build to build the same Dockerfile.
  3. Examine the image layer.

Dockerfile

FROM alpine

RUN apk add --no-cache bash

COPY . /app

RUN chmod +x /app/hello.sh

CMD /app/hello.sh

Build

$ docker build -t img0 .
Sending build context to Docker daemon  3.072kB
Step 1/5 : FROM alpine
latest: Pulling from library/alpine
2408cc74d12b: Pull complete 
Digest: sha256:686d8c9dfa6f3ccfc8230bc3178d23f84eeaf7e457f36f271ab1acc53015037c
Status: Downloaded newer image for alpine:latest
 ---> e66264b98777
Step 2/5 : RUN apk add --no-cache bash
 ---> Running in 8d4bb9012c59
fetch https://dl-cdn.alpinelinux.org/alpine/v3.16/main/x86_64/APKINDEX.tar.gz
fetch https://dl-cdn.alpinelinux.org/alpine/v3.16/community/x86_64/APKINDEX.tar.gz
(1/4) Installing ncurses-terminfo-base (6.3_p20220521-r0)
(2/4) Installing ncurses-libs (6.3_p20220521-r0)
(3/4) Installing readline (8.1.2-r0)
(4/4) Installing bash (5.1.16-r2)
Executing bash-5.1.16-r2.post-install
Executing busybox-1.35.0-r13.trigger
OK: 8 MiB in 18 packages
Removing intermediate container 8d4bb9012c59
 ---> c30c4ade8d67
Step 3/5 : COPY . /app
 ---> 14ab7c71e803
Step 4/5 : RUN chmod +x /app/hello.sh
 ---> Running in 8fc8c2d9a28e
Removing intermediate container 8fc8c2d9a28e
 ---> f11502e3c083
Step 5/5 : CMD /app/hello.sh
 ---> Running in 3f00d75f1bd4
Removing intermediate container 3f00d75f1bd4
 ---> a7323ea78a43
Successfully built a7323ea78a43
Successfully tagged img0:latest
$ docker buildx build -t img1 .
[+] Building 4.6s (9/9) FINISHED                                                                                                                                         
 => [internal] load build definition from Dockerfile                                                                                                                0.0s
 => => transferring dockerfile: 137B                                                                                                                                0.0s
 => [internal] load .dockerignore                                                                                                                                   0.0s
 => => transferring context: 2B                                                                                                                                     0.0s
 => [internal] load metadata for docker.io/library/alpine:latest                                                                                                    0.0s
 => [1/4] FROM docker.io/library/alpine                                                                                                                             0.0s
 => [internal] load build context                                                                                                                                   0.0s
 => => transferring context: 212B                                                                                                                                   0.0s
 => [2/4] RUN apk add --no-cache bash                                                                                                                               3.9s
 => [3/4] COPY . /app                                                                                                                                               0.0s 
 => [4/4] RUN chmod +x /app/hello.sh                                                                                                                                0.4s 
 => exporting to image                                                                                                                                              0.1s 
 => => exporting layers                                                                                                                                             0.1s 
 => => writing image sha256:c6cfc6f9688fb5aca23bfc128cb326c90d07ae420456f3c3a0b558ec7f0bfc6c                                                                        0.0s 
 => => naming to docker.io/library/img1

View Layers

$ docker image history img0
IMAGE          CREATED         CREATED BY                                      SIZE      COMMENT
a7323ea78a43   2 minutes ago   /bin/sh -c #(nop)  CMD ["/bin/sh" "-c" "/app…   0B        
f11502e3c083   2 minutes ago   /bin/sh -c chmod +x /app/hello.sh               38B       
14ab7c71e803   2 minutes ago   /bin/sh -c #(nop) COPY dir:d7e62b3bbd2c3347c…   138B      
c30c4ade8d67   2 minutes ago   /bin/sh -c apk add --no-cache bash              2.15MB    
e66264b98777   6 weeks ago     /bin/sh -c #(nop)  CMD ["/bin/sh"]              0B        
<missing>      6 weeks ago     /bin/sh -c #(nop) ADD file:8e81116368669ed3d…   5.53MB   
$ docker image history img1
IMAGE          CREATED          CREATED BY                                      SIZE      COMMENT
c6cfc6f9688f   38 seconds ago   CMD ["/bin/sh" "-c" "/app/hello.sh"]            0B        buildkit.dockerfile.v0
<missing>      38 seconds ago   RUN /bin/sh -c chmod +x /app/hello.sh # buil…   38B       buildkit.dockerfile.v0
<missing>      39 seconds ago   COPY . /app # buildkit                          138B      buildkit.dockerfile.v0
<missing>      39 seconds ago   RUN /bin/sh -c apk add --no-cache bash # bui…   2.15MB    buildkit.dockerfile.v0
<missing>      6 weeks ago      /bin/sh -c #(nop)  CMD ["/bin/sh"]              0B        
<missing>      6 weeks ago      /bin/sh -c #(nop) ADD file:8e81116368669ed3d…   5.53MB  

Inspect the Top Layer

$ docker image inspect a7323ea78a43
[
    {
        "Id": "sha256:a7323ea78a43a11df6abe8eccd920621e8b595cf23875cb246f0538aaf75c6ff",
        "RepoTags": [
            "img0:latest"
        ],
        "RepoDigests": [],
        "Parent": "sha256:f11502e3c08353b0504528c22cb09b677d8afbfc4956a95870925e5968363543",
        "Comment": "",
        "Created": "2022-07-06T12:40:27.051022433Z",
        "Container": "3f00d75f1bd4383bfc75e7aae5024e22e0f2099451ab84223dfe565d96e8624a",
        "ContainerConfig": {
            "Hostname": "3f00d75f1bd4",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
            ],
            "Cmd": [
                "/bin/sh",
                "-c",
                "#(nop) ",
                "CMD [\"/bin/sh\" \"-c\" \"/app/hello.sh\"]"
            ],
            "Image": "sha256:f11502e3c08353b0504528c22cb09b677d8afbfc4956a95870925e5968363543",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": null,
            "Labels": {}
        },
        "DockerVersion": "20.10.17",
        "Author": "",
        "Config": {
            "Hostname": "",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
            ],
            "Cmd": [
                "/bin/sh",
                "-c",
                "/app/hello.sh"
            ],
            "Image": "sha256:f11502e3c08353b0504528c22cb09b677d8afbfc4956a95870925e5968363543",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": null,
            "Labels": null
        },
        "Architecture": "amd64",
        "Os": "linux",
        "Size": 7677757,
        "VirtualSize": 7677757,
        "GraphDriver": {
            "Data": {
                "LowerDir": "/var/lib/docker/overlay2/13307c9f5368dc3ffe7f835b64d6dd8f843c604f2679fa5ee08f241db98bf5ce/diff:/var/lib/docker/overlay2/1e3797cb8f3c5c499f1bd5a9b9fd76b0452350b15724c42340330d8c12b6249a/diff:/var/lib/docker/overlay2/9f7f7dbdc8dd5732b0da5aec52cd16f9a144181533bb02134ef990d3fd313624/diff",
                "MergedDir": "/var/lib/docker/overlay2/11d90a52784c4bfe1405fa6d3fd5bcaacf47365354dd56e887d3b16413144b86/merged",
                "UpperDir": "/var/lib/docker/overlay2/11d90a52784c4bfe1405fa6d3fd5bcaacf47365354dd56e887d3b16413144b86/diff",
                "WorkDir": "/var/lib/docker/overlay2/11d90a52784c4bfe1405fa6d3fd5bcaacf47365354dd56e887d3b16413144b86/work"
            },
            "Name": "overlay2"
        },
        "RootFS": {
            "Type": "layers",
            "Layers": [
                "sha256:24302eb7d9085da80f016e7e4ae55417e412fb7e0a8021e95e3b60c67cde557d",
                "sha256:25ece83ddc8aa2e3aed147f65c223cfe6eede2e99852af949144e0bc92fe720c",
                "sha256:d520722da3f37c656c0d1730ecbb2c935be859a26f1d5725cb9bed839fa58804",
                "sha256:9045588752f71bdd537f2d634818739acf9d275e86ea2479a2139a19a1847079"
            ]
        },
        "Metadata": {
            "LastTagTime": "2022-07-06T20:43:02.062852034+08:00"
        }
    }
]
$ docker image inspect c6cfc6f9688f
[
    {
        "Id": "sha256:c6cfc6f9688fb5aca23bfc128cb326c90d07ae420456f3c3a0b558ec7f0bfc6c",
        "RepoTags": [
            "img1:latest"
        ],
        "RepoDigests": [],
        "Parent": "",
        "Comment": "buildkit.dockerfile.v0",
        "Created": "2022-07-06T20:42:49.076111009+08:00",
        "Container": "",
        "ContainerConfig": {
            "Hostname": "",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": null,
            "Cmd": null,
            "Image": "",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": null,
            "Labels": null
        },
        "DockerVersion": "",
        "Author": "",
        "Config": {
            "Hostname": "",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
            ],
            "Cmd": [
                "/bin/sh",
                "-c",
                "/app/hello.sh"
            ],
            "ArgsEscaped": true,
            "Image": "",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": null,
            "Labels": null
        },
        "Architecture": "amd64",
        "Os": "linux",
        "Size": 7677675,
        "VirtualSize": 7677675,
        "GraphDriver": {
            "Data": {
                "LowerDir": "/var/lib/docker/overlay2/c8k5fvkar7hk9tu8tj6jaeox1/diff:/var/lib/docker/overlay2/46yyctaxts7ssul5ie8rd450s/diff:/var/lib/docker/overlay2/9f7f7dbdc8dd5732b0da5aec52cd16f9a144181533bb02134ef990d3fd313624/diff",
                "MergedDir": "/var/lib/docker/overlay2/o8uhrtev6jlr4z8pxvuz2rl3c/merged",
                "UpperDir": "/var/lib/docker/overlay2/o8uhrtev6jlr4z8pxvuz2rl3c/diff",
                "WorkDir": "/var/lib/docker/overlay2/o8uhrtev6jlr4z8pxvuz2rl3c/work"
            },
            "Name": "overlay2"
        },
        "RootFS": {
            "Type": "layers",
            "Layers": [
                "sha256:24302eb7d9085da80f016e7e4ae55417e412fb7e0a8021e95e3b60c67cde557d",
                "sha256:30b9f345d55995a166db38ec93a7b59efb84b14d886dbebe80c3328e9d3f08a1",
                "sha256:822031192040976c804ae851b7c2792f98790e3e370a837de09d2050b1d07e0c",
                "sha256:0383043465c7d472e68115983939bc58e374e9a8283dd8b0538a1be7fe3d6807"
            ]
        },
        "Metadata": {
            "LastTagTime": "0001-01-01T00:00:00Z"
        }
    }
]
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