最大的好处，我觉得莫过于资源共享了！比如有多个镜像都从相同的Base镜像构建而来，那么宿主机
只需在磁盘上保留一份base镜像，同时内存中也只需要加载一份base镜像，这样就可以为所有的容器
服务了，而且镜像的每一层都可以被共享。
总结：
所有的 Docker镜像都起始于一个基础镜像层，当进行修改或培加新的内容时，就会在当前镜像层之
上，创建新的镜像层。Docker 镜像都是只读的，当容器启动时，一个新的可写层加载到镜像的顶部！这一层就是我们通常说的容器层，容器之下的都叫镜像层！
查看docker镜像分层信息
命令：docker inspect 镜像id或镜像名称
[root@ecs-x-large-2-linux-20200305213344 ~]# docker inspect d00afcde654e [ { "Id": "sha256:d00afcde654e3125384d52fb872c88986d2046fa598a12abcee52ff0d98e7562", "RepoTags": [ "docker.io/redis:5.0" ], "RepoDigests": [ "docker.io/redis@sha256:6ba62effb31d8d74e6e2dec4b7ef9c8985e7fcc85c4f179e13f622f5785a4135" ], "Parent": "", "Comment": "", "Created": "2021-03-02T23:29:46.396151327Z", "Container": "6a7820655f2592fdc2b254036170652520beb98f79a41e6aedc17987ccec3829", "ContainerConfig": { "Hostname": "6a7820655f25", "Domainname": "", "User": "", "AttachStdin": false, "AttachStdout": false, "AttachStderr": false, "ExposedPorts": { "6379/tcp": {} }, "Tty": false, "OpenStdin": false, "StdinOnce": false, "Env": [ "PATH=http://www.likecs.com/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin", "GOSU_VERSION=1.12", "REDIS_VERSION=5.0.12", "REDIS_DOWNLOAD_URL=http://download.redis.io/releases/redis-5.0.12.tar.gz", "REDIS_DOWNLOAD_SHA=7040eba5910f7c3d38f05ea5a1d88b480488215bdbd2e10ec70d18380108e31e" ], "Cmd": [ "/bin/sh", "-c", "#(nop) ", "CMD [\"redis-server\"]" ], "Image": "sha256:f43399b52be67a391b4bf53e210c55002a2bce5e4fa5f1021d4dc9725ec7f537", "Volumes": { "/data": {} }, "WorkingDir": "/data", "Entrypoint": [ "docker-entrypoint.sh" ], "OnBuild": null, "Labels": {} }, "DockerVersion": "19.03.12", "Author": "", "Config": { "Hostname": "", "Domainname": "", "User": "", "AttachStdin": false, "AttachStdout": false, "AttachStderr": false, "ExposedPorts": { "6379/tcp": {} }, "Tty": false, "OpenStdin": false, "StdinOnce": false, "Env": [ "PATH=http://www.likecs.com/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin", "GOSU_VERSION=1.12", "REDIS_VERSION=5.0.12", "REDIS_DOWNLOAD_URL=http://download.redis.io/releases/redis-5.0.12.tar.gz", "REDIS_DOWNLOAD_SHA=7040eba5910f7c3d38f05ea5a1d88b480488215bdbd2e10ec70d18380108e31e" ], "Cmd": [ "redis-server" ], "Image": "sha256:f43399b52be67a391b4bf53e210c55002a2bce5e4fa5f1021d4dc9725ec7f537", "Volumes": { "/data": {} }, "WorkingDir": "/data", "Entrypoint": [ "docker-entrypoint.sh" ], "OnBuild": null, "Labels": null }, "Architecture": "amd64", "Os": "linux", "Size": 98358570, "VirtualSize": 98358570, "GraphDriver": { "Name": "overlay2", "Data": { "LowerDir": "/var/lib/docker/overlay2/343be33bc297acdf8bc2b57b335c025ea76b8d1263548ba269c0aefb81aaf28d/diff:/var/lib/docker/overlay2/3302ce8415cd3a8a1e1e9753eebbb38df5b15cc02fef109e30be41f4310ee810/diff:/var/lib/docker/overlay2/44c8b45db6fd63960703e604f43a4acc5633f09a3a91a8d7263ad2f9bfd0d038/diff:/var/lib/docker/overlay2/5eb368e142c6079aa1f507149216281ca79b5df08ba19bad51390d74dfbf3c1f/diff:/var/lib/docker/overlay2/219cf0492ba08d03dc4f2a5649ec1124fff82ebe22c6f9a0a26ccf303be0e0d1/diff", "MergedDir": "/var/lib/docker/overlay2/d38f31592715a55459f4556623786c5878014bf8ffdcc1e88506069e32ba75dc/merged", "UpperDir": "/var/lib/docker/overlay2/d38f31592715a55459f4556623786c5878014bf8ffdcc1e88506069e32ba75dc/diff", "WorkDir": "/var/lib/docker/overlay2/d38f31592715a55459f4556623786c5878014bf8ffdcc1e88506069e32ba75dc/work" } }, "RootFS": { "Type": "layers", "Layers": [ #镜像分层信息 "sha256:9eb82f04c782ef3f5ca25911e60d75e441ce0fe82e49f0dbf02c81a3161d1300", "sha256:f973e3e0e07c6e9f9418a6dd0c453cd70c7fb87a0826172275883ab4bdb61bf4", "sha256:c16b4f3a3f99ebbcd59795b54faf4cdf2e00ee09b85124fda5d0746d64237ca6", "sha256:01b7eeecc774b7669892f89fc8b84eea781263448978a411f0f429b867410fc5", "sha256:f2df42e57d5eef289656ef8aad072d2828a61e93833e2928a789a88bc2bc1cbc", "sha256:b537eb7339bcbff729ebdc63a0f910b39ae3d5540663a74f55081b62e92f66e3" ] } } ]