Docker 1.13引入了docker system df命令，类似于Linux上的df命令，用于查看Docker的磁盘使用情况。
$ docker system df TYPE TOTAL ACTIVE SIZE RECLAIMABLE Images 3 0 5.373GB 5.373GB (100%) Containers 0 0 0B 0B Local Volumes 0 0 0B 0B
查看单个image、container大小：docker system df -v
[root@localhost ~]# docker system df -v Images space usage: REPOSITORY TAG IMAGE ID CREATED SIZE SHARED SIZE UNIQUE SIZE CONTAINERS mongo latest 66c68b650ad4 5 weeks ago 387.8MB 64.21MB 323.6MB 1 rabbitmq management 1c1e1f201079 7 weeks ago 181.5MB 151.4MB 30.09MB 1 rabbitmq latest 3e5ddca64bb7 7 weeks ago 151.4MB 151.4MB 0B 0 Containers space usage: CONTAINER ID IMAGE COMMAND LOCAL VOLUMES SIZE CREATED STATUS NAMES 1a0bb1ac1c52 mongo "docker-entrypoint.s…" 1 2.74MB 5 weeks ago Up 7 hours docker_mongodb 73417264c538 rabbitmq:management "docker-entrypoint.s…" 1 1.73kB 6 weeks ago Exited (255) 2 days ago rabbitmq Local Volumes space usage: VOLUME NAME LINKS SIZE 13856e3cfd4af0a2d695cca746c4039213a66901c43326a3c14391c61bf07d21 0 285.6MB 2e7a18c2cde8bc82ad145138d495b3bdfe7329870a130874ef11aff57df2a955 1 0B 556df6317f798afb15cf6bdc8c6763ab45cabf2b09304545bcd319049ff61cef 1 338.9MB e7c82573f88c7e083445cbc611ed753ab26e36c73964fed323f7e38e3cb431b4 0 440.5MB Build cache usage: 0B CACHE ID CACHE TYPE SIZE CREATED LAST USED USAGE SHARED
Docker提供了docker system prune，可以用于清理dangling镜像(参考What are Docker <none>:<none> images?)和容器，以及失效的数据卷和网络。
$ docker system prune WARNING! This will remove: - all stopped containers - all volumes not used by at least one container - all networks not used by at least one container - all dangling images Are you sure you want to continue? [y/N] y Deleted Containers: 1cdf866157b4a97e151125af3c2a7f186a59b6f63807e2014ce1a00d68f44e1d Deleted Images: deleted: sha256:f59bb277... deleted: sha256:695b8e70... deleted: sha256:93b1cceb... deleted: sha256:c74d6bcd... deleted: sha256:df8b9bb1... deleted: sha256:dfe8340f... deleted: sha256:ce1ee654... Total reclaimed space: 3.221GB
名称为<none>:<none>，为dangling镜像，因此会被删除。同时，所有的中间镜像也会被删除。
更进一步，使用-a选项可以做深度清理。这时我们会看到更加严重的WARNING信息:
$ docker system prune -a WARNING! This will remove: - all stopped containers - all volumes not used by at least one container - all networks not used by at least one container - all images without at least one container associated to them Are you sure you want to continue? [y/N] y Deleted Images: untagged: test:latest deleted: sha256:c515ebfa2... deleted: sha256:07302c011... deleted: sha256:37c0c6474... deleted: sha256:5cc2b6bc4... deleted: sha256:b283b9c35... deleted: sha256:8a8b9bd8b... untagged: alpine:latest untagged: alpine@sha256:58e1a1bb75db1... deleted: sha256:4a415e366... deleted: sha256:23b9c7b43... Total reclaimed space: 2.151GB
这个命令将清理整个系统，并且只会保留真正在使用的镜像，容器，数据卷以及网络，因此需要格外谨慎。比如，我们不能在生产环境中运行prune -a命令，因为一些备用镜像(用于备份，回滚等)有时候需要用到，如果这些镜像被删除了，则运行容器时需要重新下载。
此时，所有未绑定容器的镜像将会被删除。由于第一次prune命令删除了所有容器，因此所有镜像(它们没有绑定任何容器)都会被删除。
参考：
https://blog.csdn.net/dmw412724/article/details/107126828
http://dockone.io/article/2258