docker system命令集合的使用

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[root@localhost ~]# docker system --help

Usage:  docker system COMMAND

Manage Docker

Options:
      --help   Print usage

Commands:
  df          Show docker disk usage
  events      Get real time events from the server
  info        Display system-wide information
  prune       Remove unused data

Run 'docker system COMMAND --help' for more information on a command.
[root@localhost ~]#

docker system df

提供Docker整体磁盘使用率的概况，包括镜像、容器和（本地）volume。所以我们现在随时都可以查看Docker使用了多少资源。

[root@localhost ~]# docker system df
TYPE                TOTAL               ACTIVE              SIZE                RECLAIMABLE
Images              10                  6                   2.652GB             1.953GB (73%)
Containers          6                   6                   6.922MB             0B (0%)
Local Volumes       0                   0                   0B                  0B
[root@localhost ~]#

docker system prune

如果之前的命令展示出 docker 已经占用了太多空间，我们会开始清理。有一个包办一切的命令：

[root@localhost ~]# docker system prune
WARNING! This will remove:
        - all stopped containers # 清理停止的容器
        - all networks not used by at least one container #清理没有使用的网络
        - all dangling images #清理废弃的镜像
        - all build cache #清理构建缓存
Are you sure you want to continue? [y/N] y
Total reclaimed space: 0B
[root@localhost ~]#

根据警告信息可知，这个命令会删除所有关闭的容器以及dangling镜像。示例中，含有3个1GB随机文件的镜像的名称被占用了，名称为:，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。

docker systemc info （docker info）

这个命令的缩写docker info相信大家都很熟悉

[root@localhost ~]# docker system info
Containers: 6
 Running: 6
 Paused: 0
 Stopped: 0
Images: 49
Server Version: 17.06.2-ce
Storage Driver: overlay
 Backing Filesystem: xfs
 Supports d_type: true
Logging Driver: json-file
Cgroup Driver: cgroupfs
Plugins: 
 Volume: local
 Network: bridge host macvlan null overlay
 Log: awslogs fluentd gcplogs gelf journald json-file logentries splunk syslog
Swarm: inactive
Runtimes: runc
Default Runtime: runc
Init Binary: docker-init
containerd version: 6e23458c129b551d5c9871e5174f6b1b7f6d1170
runc version: 810190ceaa507aa2727d7ae6f4790c76ec150bd2
init version: 949e6fa
Security Options:
 seccomp
  Profile: default
Kernel Version: 3.10.0-514.26.2.el7.x86_64
Operating System: CentOS Linux 7 (Core)
OSType: linux
Architecture: x86_64
CPUs: 24
Total Memory: 31.21GiB
Name: localhost.localdomain
ID: YTL2:6RWX:IZK6:X4XC:XKMO:WVXD:LXPR:E5GN:GEJB:WIUX:L5YH:PDFB
Docker Root Dir: /var/lib/docker
Debug Mode (client): false
Debug Mode (server): false
Registry: https://index.docker.io/v1/
Experimental: false
Insecure Registries:
 127.0.0.0/8
Registry Mirrors:
 http://9zkjjecg.mirror.aliyuncs.com/
 https://docker.mirrors.ustc.edu.cn/
Live Restore Enabled: false

[root@localhost ~]#

详细的解释

元字符	描述
info 等同于 docker info	查看整个docker系统的信息例如 docker system info 例如 docker system info \| grep Images
events 等同于 docker events	获取docker系统实时事件，不包括容器内的。例如：docker system events –until 1499305500 // 截止到 2017.7.6 01:45:00的操作例如：docker system events –since 1499305500 // 从 2017.7.6 01:45:00之后的操作
df	整体磁盘的使用情况例如：docker system df 例如：docker system df -v
prune	清理资源，此操作尤其需要注意。例如：docker system prune #包括清理以下的四种，即容器、镜像、数据卷、网络 – all stopped containers – all volumes not used by at least one container – all networks not used by at least one container – all dangling images 例如：docker system prune -a #包括以下的四种情况，主要和上比较 – 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