Docker 1.13引入了docker system df命令，類似於Linux上的df命令，用於檢視Docker的磁碟使用情況。

$ 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

檢視單個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，可以用於清理dangling映象(參考What are Docker <none>:<none> images?)和容器，以及失效的資料卷和網路。

$ 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

名稱為<none>:<none>，為dangling映象，因此會被刪除。同時，所有的中間映象也會被刪除。

更進一步，使用-a選項可以做深度清理。這時我們會看到更加嚴重的WARNING資訊:

$ 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

這個命令將清理整個系統，並且只會保留真正在使用的映象，容器，資料卷以及網路，因此需要格外謹慎。比如，我們不能在生產環境中執行prune -a命令，因為一些備用映象(用於備份，回滾等)有時候需要用到，如果這些映象被刪除了，則執行容器時需要重新下載。

此時，所有未繫結容器的映象將會被刪除。由於第一次prune命令刪除了所有容器，因此所有映象(它們沒有繫結任何容器)都會被刪除。

參考：

https://blog.csdn.net/dmw412724/article/details/107126828

http://dockone.io/article/2258