docker cp[选项]SRC_PATH容器：DEST_PATH

DEST_PATH必须预先存在

在主机系统（容器外部）上创建一个数据目录，并将其装载到容器内部可见的目录中。这将文件放置在主机系统上的已知位置，并使主机系统中的工具和应用程序可以轻松访问文件

docker run -d -v /path/to/Local_host_dir:/path/to/docker_dir docker_image:tag

如果您只想从映像（而不是正在运行的容器）中提取文件，可以执行以下操作：

docker运行--rm＜image＞cat＜source＞＞＜local_dest＞

这将打开容器，写入新文件，然后删除容器。然而，一个缺点是文件权限和修改日期不会被保留。

创建要复制文件的路径，然后使用：

docker run -d -v hostpath:dockerimag

docker cp[选项]SRC_PATH容器：DEST_PATH

DEST_PATH必须预先存在

随着Docker 19.03的发布，您可以跳过创建容器甚至构建映像。基于BuildKit的构建有一个选项可以更改输出目标。您可以使用它将构建结果写入本地目录，而不是写入映像。例如，这里是go二进制文件的构建：

$ ls
Dockerfile  go.mod  main.go

$ cat Dockerfile
FROM golang:1.12-alpine as dev
RUN apk add --no-cache git ca-certificates
RUN adduser -D appuser
WORKDIR /src
COPY . /src/
CMD CGO_ENABLED=0 go build -o app . && ./app

FROM dev as build
RUN CGO_ENABLED=0 go build -o app .
USER appuser
CMD [ "./app" ]

FROM scratch as release
COPY --from=build /etc/passwd /etc/group /etc/
COPY --from=build /src/app /app
USER appuser
CMD [ "/app" ]

FROM scratch as artifact
COPY --from=build /src/app /app

FROM release

从上面的Dockerfile中，我构建的工件阶段只包含我想要导出的文件。新引入的--output标志允许我将它们写入本地目录，而不是图像。这需要使用19.03附带的BuildKit引擎执行：

$ DOCKER_BUILDKIT=1 docker build --target artifact --output type=local,dest=. .
[+] Building 43.5s (12/12) FINISHED
 => [internal] load build definition from Dockerfile                                                                              0.7s
 => => transferring dockerfile: 572B                                                                                              0.0s
 => [internal] load .dockerignore                                                                                                 0.5s
 => => transferring context: 2B                                                                                                   0.0s
 => [internal] load metadata for docker.io/library/golang:1.12-alpine                                                             0.9s
 => [dev 1/5] FROM docker.io/library/golang:1.12-alpine@sha256:50deab916cce57a792cd88af3479d127a9ec571692a1a9c22109532c0d0499a0  22.5s
 => => resolve docker.io/library/golang:1.12-alpine@sha256:50deab916cce57a792cd88af3479d127a9ec571692a1a9c22109532c0d0499a0       0.0s
 => => sha256:1ec62c064901392a6722bb47a377c01a381f4482b1ce094b6d28682b6b6279fd 155B / 155B                                        0.3s
 => => sha256:50deab916cce57a792cd88af3479d127a9ec571692a1a9c22109532c0d0499a0 1.65kB / 1.65kB                                    0.0s
 => => sha256:2ecd820bec717ec5a8cdc2a1ae04887ed9b46c996f515abc481cac43a12628da 1.36kB / 1.36kB                                    0.0s
 => => sha256:6a17089e5a3afc489e5b6c118cd46eda66b2d5361f309d8d4b0dcac268a47b13 3.81kB / 3.81kB                                    0.0s
 => => sha256:89d9c30c1d48bac627e5c6cb0d1ed1eec28e7dbdfbcc04712e4c79c0f83faf17 2.79MB / 2.79MB                                    0.6s
 => => sha256:8ef94372a977c02d425f12c8cbda5416e372b7a869a6c2b20342c589dba3eae5 301.72kB / 301.72kB                                0.4s
 => => sha256:025f14a3d97f92c07a07446e7ea8933b86068d00da9e252cf3277e9347b6fe69 125.33MB / 125.33MB                               13.7s
 => => sha256:7047deb9704134ff71c99791be3f6474bb45bc3971dde9257ef9186d7cb156db 125B / 125B                                        0.8s
 => => extracting sha256:89d9c30c1d48bac627e5c6cb0d1ed1eec28e7dbdfbcc04712e4c79c0f83faf17                                         0.2s
 => => extracting sha256:8ef94372a977c02d425f12c8cbda5416e372b7a869a6c2b20342c589dba3eae5                                         0.1s
 => => extracting sha256:1ec62c064901392a6722bb47a377c01a381f4482b1ce094b6d28682b6b6279fd                                         0.0s
 => => extracting sha256:025f14a3d97f92c07a07446e7ea8933b86068d00da9e252cf3277e9347b6fe69                                         5.2s
 => => extracting sha256:7047deb9704134ff71c99791be3f6474bb45bc3971dde9257ef9186d7cb156db                                         0.0s
 => [internal] load build context                                                                                                 0.3s
 => => transferring context: 2.11kB                                                                                               0.0s
 => [dev 2/5] RUN apk add --no-cache git ca-certificates                                                                          3.8s
 => [dev 3/5] RUN adduser -D appuser                                                                                              1.7s
 => [dev 4/5] WORKDIR /src                                                                                                        0.5s
 => [dev 5/5] COPY . /src/                                                                                                        0.4s
 => [build 1/1] RUN CGO_ENABLED=0 go build -o app .                                                                              11.6s
 => [artifact 1/1] COPY --from=build /src/app /app                                                                                0.5s
 => exporting to client                                                                                                           0.1s
 => => copying files 10.00MB                                                                                                      0.1s

构建完成后，将导出应用程序二进制文件：

$ ls
Dockerfile  app  go.mod  main.go

$ ./app
Ready to receive requests on port 8080

Docker对上游BuildKit repo中记录的--output标志有其他选项：https://github.com/moby/buildkit#output