3、docker入门

docker状态

docker info

该命令会返回所有容器和镜像的数量、docker使用的驱动程序和存储驱动,以及docker的基本配置信息

创建/运行第一个容器

使用docker run命令创建容器,此命令提供了容器的创建到启动的功能

root@doushuo-virtual-machine:~# docker run -i -t ubuntu /bin/bash
Unable to find image 'ubuntu:latest' locally
latest: Pulling from library/ubuntu
ae79f2514705: Pull complete
6f01dc62e444: Download complete
5ad56d5fc149: Pull complete 
170e558760e8: Pull complete 
395460e233f5: Pull complete 
6f01dc62e444: Pull complete
Digest: sha256:506e2d5852de1d7c90d538c5332bd3cc33b9cbd26f6ca653875899c505c82687
Status: Downloaded newer image for ubuntu:latest
root@82a9aa3f8f4d:/#

首先,docker会检查本地是否存在ubuntu镜像,如果没有就会连接官方维护的Docker Hub Registry,查找是否有此镜像,如果有就会下载并保存在本地宿主机上。
随后,docker在文件系统内部用这个镜像创建了一个新容器,它拥有自己的网络、IP地址,以及一个来和宿主机进行通信的桥接网络接口。

  • docker run:创建并启动一个容器
  • -i :保证容器中的STDIN是开启的,即是前台实时交互的,而不是后台运行
  • -t :指示docker要为创建的容器分配一个可交互的伪tty终端
  • ubuntu:指示基于什么镜像来创建容器。Ubuntu镜像是一个常备镜像,也称为基础镜像,由docker公司提供,保存在Docker Hub Registry上。
    我们可以以这个ubuntu镜像为基础,在此上构建属于自己的镜像。到目前为止,仅仅构建了一个ubuntu容器,并没有增加任何东西。
  • /bin/bash:启动了一个Bash shell,代码块中前后的shell不是一个

使用第一个容器

这是一个完整的ubuntu系统,可以用它来做任何事情。容器ID:82a9aa3f8f4d
查看容器主机名

root@82a9aa3f8f4d:~# hostname
82a9aa3f8f4d

检查容器的/etc/hosts文件

root@82a9aa3f8f4d:~# cat /etc/hosts
127.0.0.1   localhost
::1 localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
172.17.0.2  82a9aa3f8f4d

docker已经在hosts文件中为该容器的IP地址添加了一条主机配置项
查看容器网络接口

root@82a9aa3f8f4d:/# ifconfig 
eth0      Link encap:Ethernet  HWaddr 02:42:ac:11:00:02  
          inet addr:172.17.0.2  Bcast:0.0.0.0  Mask:255.255.0.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:15165 errors:0 dropped:0 overruns:0 frame:0
          TX packets:11515 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:46810862 (46.8 MB)  TX bytes:636176 (636.1 KB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

查看进程

root@82a9aa3f8f4d:/# ps -aux
USER        PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root          1  0.0  0.3  18332  3232 ?        Ss   13:22   0:00 /bin/bash
root        791  0.0  0.2  34428  2792 ?        R+   13:48   0:00 ps -aux

安装软件包

apt-get update
apt-get install vim 

退出容器

root@82a9aa3f8f4d:/# exit
exit
root@doushuo-virtual-machine:~# 

返回宿主机,但是容器也随机停止运行了
只有在指定/bin/bash命令处于运行状态的时候,容器才会相应的处于运行状态,但是容器依然存在:

root@doushuo-virtual-machine:~# docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
root@doushuo-virtual-machine:~# docker ps -a
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS                          PORTS               NAMES
82a9aa3f8f4d        ubuntu              "/bin/bash"         About an hour ago   Exited (0) About a minute ago                       determined_hamilton

指定容器可以通过短ID、长ID、容器名称来指定

容器命名

docker run --name test -i -t ubuntu /bin/bash

这样会创建一个名为test的docker容器,以Ubuntu为镜像

重新启动一个容器

退出容器之后,必须要用docker ps -a才能查看到所有容器,下面来启动一个已经存在的容器:

docker start [docker_name]
docker start [docker_ID]

也可以选择重新启动已经运行的容器:

docker restart [docker_name/docker_ID]

附着到容器上

使用start或者restart命令仅仅是启动了容器,并没有与之进行交互。
使用attach命令重新附着到一个容器的会话上:

root@doushuo-virtual-machine:~# docker ps -a 
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS                     PORTS               NAMES
d3efdb7fc09c        ubuntu              "/bin/bash"         14 seconds ago      Exited (0) 6 seconds ago                       doushuo
82a9aa3f8f4d        ubuntu              "/bin/bash"         5 weeks ago         Exited (0) 5 weeks ago                         determined_hamilton
root@doushuo-virtual-machine:~# docker start 82a9a
82a9a
root@doushuo-virtual-machine:~# docker ps 
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
82a9aa3f8f4d        ubuntu              "/bin/bash"         5 weeks ago         Up 6 seconds                            determined_hamilton
root@doushuo-virtual-machine:~# docker attach deter
Error: No such container: deter
root@doushuo-virtual-machine:~# docker attach determined_hamilton
root@82a9aa3f8f4d:/# 

创建守护式容器

  • 交互式容器,可以进行交互操作等
  • 守护式容器,没有交互式会话,非常适合运行服务和应用程序
    通常情况下都是使用守护式容器
root@doushuo-virtual-machine:~# docker run --name daemon_dave -d ubuntu /bin/bash -c "while true; do echo hello world; sleep 1;done"
a74c40ecf2bf0059739f5db1d3aa7a6b745d88d517f8683ec4bbd6557a459574
root@doushuo-virtual-machine:~# docker ps 
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS               NAMES
a74c40ecf2bf        ubuntu              "/bin/bash -c 'whi..."   4 seconds ago       Up 4 seconds                            daemon_dave
root@doushuo-virtual-machine:~# 

这里使用了-d选项,指定容器于后台运行,所有创建之后仅仅在命令行返回了一个docker_ID而不是交互界面。

获取容器日志

只用docker logs获取容器运行的信息

root@doushuo-virtual-machine:~# docker logs daemon_dave
hello world
hello world
hello world
hello world
hello world
hello world
hello world
hello world
root@doushuo-virtual-machine:~# 

还可以加上一些参数:

  • -f 动态追踪日志,类似于tail -f
  • -t 加上时间戳查看日志
  • –tail n 查看最新的n条日志,如果为0则只查看最新的日志
root@doushuo-virtual-machine:~# docker logs daemon_dave
hello world
hello world
hello world
hello world
hello world
hello world
hello world
^C
root@doushuo-virtual-machine:~# 
root@doushuo-virtual-machine:~# docker logs --tail 0 -ft  daemon_dave
2017-10-30T08:17:50.523079296Z hello world
2017-10-30T08:17:51.527672075Z hello world
2017-10-30T08:17:52.529261165Z hello world
2017-10-30T08:17:53.531698074Z hello world
2017-10-30T08:17:54.537658244Z hello world
^C
root@doushuo-virtual-machine:~# 

docker日志驱动

自docker1.6开始,可以控制docker守护进程和容器的日志驱动了。通过--log-driver选项来实现,可以在启动守护进程或者执行docker run时使用

  • json-file 默认选项
  • syslog 将禁用docker logs命令;将对应容器的日志重定向到syslog中,在启动守护进程时指定该选项,会将所有容器的日志重定向到syslog中
  • none 禁用所有容器中的日志
root@doushuo-virtual-machine:~# docker run --log-driver="syslog" --name log_syslog -d ubuntu /bin/bash -c "while; do echo hello world ;sleep 3; done"
c97d942c5b24a5540b0313a7b1a5c272f1a1adbc743b676c0c4a981f9164474d
root@doushuo-virtual-machine:~# 
root@doushuo-virtual-machine:~# docker logs log_syslog
Error response from daemon: configured logging driver does not support reading
root@doushuo-virtual-machine:~# 
root@doushuo-virtual-machine:~# docker run --log-driver="none" --name log_none -d ubuntu /bin/sh -c "while; do echo hello world; sleep 1; done"
31c2219a7adaf238b737cafb45e78c016e124849c78dfd68a132cba7d35ffa7c
root@doushuo-virtual-machine:~# docker logs log_none
Error response from daemon: configured logging driver does not support reading
root@doushuo-virtual-machine:~# 

查看容器内的进程

使用docker top命令:

root@doushuo-virtual-machine:~# docker start daemon_dave
daemon_dave
root@doushuo-virtual-machine:~# docker top daemon_dave
UID                 PID                 PPID                C                   STIME               TTY                 TIME                CMD
root                14634               14617               0                   16:52               ?                   00:00:00            /bin/bash -c while true; do echo hello world; sleep 1;done
root                14664               14634               0                   16:52               ?                   00:00:00            sleep 1

docker统计信息

docker1.5.0中引入了docker stats命令,可以查看一个或者多个容器的状态:

root@doushuo-virtual-machine:~# docker ps -a 
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS                         PORTS               NAMES
31c2219a7ada        ubuntu              "/bin/sh -c 'while..."   15 minutes ago      Exited (2) 15 minutes ago                          log_none
c97d942c5b24        ubuntu              "/bin/bash -c 'whi..."   17 minutes ago      Exited (1) 17 minutes ago                          log_syslog
a74c40ecf2bf        ubuntu              "/bin/bash -c 'whi..."   About an hour ago   Up 10 minutes                                      daemon_dave
d3efdb7fc09c        ubuntu              "/bin/bash"              About an hour ago   Exited (0) About an hour ago                       doushuo
82a9aa3f8f4d        ubuntu              "/bin/bash"              5 weeks ago         Exited (0) About an hour ago                       determined_hamilton
root@doushuo-virtual-machine:~# docker stats log_none doushuo daemon_dave
CONTAINER           CPU %               MEM USAGE / LIMIT   MEM %               NET I/O             BLOCK I/O           PIDS
log_none            0.00%               0B / 0B             0.00%               0B / 0B             0B / 0B             0
doushuo             0.00%               0B / 0B             0.00%               0B / 0B             0B / 0B             0
daemon_dave         0.06%               444KiB / 976.8MiB   0.04%               4.74kB / 0B         0B / 0B             0

在容器内部运行进程

docker1.3之后,可以通过docker exec命令在容器内部额外启动新的进程:

  • 后台任务
  • 交互式任务

后台任务:

root@doushuo-virtual-machine:~# docker exec -d daemon_dave touch /home/doushuo.conf

-d选项指后台执行,此例会在创建一个空文件:/home/doushuo.conf

交互式任务:

root@doushuo-virtual-machine:~# docker exec -t -i daemon_dave /bin/bash
root@a74c40ecf2bf:/# ps -aux
USER        PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root          1  0.0  0.3  18032  3008 ?        Ss   08:52   0:00 /bin/bash -c while true; do echo hello world; sleep 1;done
root       1270  0.0  0.3  18244  3220 ?        Ss   09:13   0:00 /bin/bash
root       1289  0.0  0.0   4384   684 ?        S    09:14   0:00 sleep 1
root       1290  0.0  0.2  34428  2744 ?        R+   09:14   0:00 ps -aux
root@a74c40ecf2bf:/# 

类似于运行交互式容器,-t-i标志为容器创建了tty伪终端并捕捉STDIN。此例会在daemon_dave容器中创建一个新的bash会话,从而进行交互式操作。

停止守护式容器

使用docker stop命令来停止守护式(后台)容器:

docker stop [docker_name/docker_ID]

docker stop命令会向容器发送SIGTERM信号,使用docker kill命令可以快速停止容器,相当于发送SIGKILL信号。

自动重启容器

如果出于某种错误而导致容器停止运行,可以通过--restart标志,让docker自动重启该容器。--restart标志会自动检查容器退出代码,由此来决定是否重启容器,默认不会重启机器。此标志是docker1.2.0引入的选项。

docker run --restart=always  --name daemon_dave -d ubuntu /bin/sh -c "while; do echo hello world ;sleep 3; done"

无论退出代码是什么,都会重启容器

docker run --restart=on-failure  --name daemon_dave -d ubuntu /bin/sh -c "while; do echo hello world ;sleep 3; done"

只有当容器退出代码为非0值的时候,才会重启容器

docker run --restart=on-failure:5  --name daemon_dave -d ubuntu /bin/sh -c "while; do echo hello world ;sleep 3; done"

退出代码非0值,尝试重启容器,最多重启5次。

深入容器

使用docker inspect命令来获取更多的容器信息:

root@doushuo-virtual-machine:~# docker inspect daemon_dave
[
    {
        "Id": "a74c40ecf2bf0059739f5db1d3aa7a6b745d88d517f8683ec4bbd6557a459574",
        "Created": "2017-10-30T08:10:45.238282111Z",
        "Path": "/bin/bash",
        "Args": [
            "-c",
            "while true; do echo hello world; sleep 1;done"
        ],
        "State": {
            "Status": "running",
            "Running": true,
            "Paused": false,
            "Restarting": false,
            "OOMKilled": false,
            "Dead": false,
            "Pid": 14634,
            "ExitCode": 0,
            "Error": "",
            "StartedAt": "2017-10-30T08:52:46.317099001Z",
            "FinishedAt": "2017-10-30T08:33:25.94086388Z"
        },
        "Image": "sha256:747cb2d60bbecbda48aff14a8be5c8b913ca69318a6067e57c697f8a78dda06e",
        "ResolvConfPath": "/var/lib/docker/containers/a74c40ecf2bf0059739f5db1d3aa7a6b745d88d517f8683ec4bbd6557a459574/resolv.conf",
        "HostnamePath": "/var/lib/docker/containers/a74c40ecf2bf0059739f5db1d3aa7a6b745d88d517f8683ec4bbd6557a459574/hostname",
        "HostsPath": "/var/lib/docker/containers/a74c40ecf2bf0059739f5db1d3aa7a6b745d88d517f8683ec4bbd6557a459574/hosts",
        "LogPath": "/var/lib/docker/containers/a74c40ecf2bf0059739f5db1d3aa7a6b745d88d517f8683ec4bbd6557a459574/a74c40ecf2bf0059739f5db1d3aa7a6b745d88d517f8683ec4bbd6557a459574-json.log",
        "Name": "/daemon_dave",
        "RestartCount": 0,
        "Driver": "aufs",
        "MountLabel": "",
        "ProcessLabel": "",
        "AppArmorProfile": "docker-default",
        "ExecIDs": null,
        "HostConfig": {
            "Binds": null,
            "ContainerIDFile": "",
            "LogConfig": {
                "Type": "json-file",
                "Config": {}
            },
            "NetworkMode": "default",
            "PortBindings": {},
            "RestartPolicy": {
                "Name": "no",
                "MaximumRetryCount": 0
            },
            "AutoRemove": false,
            "VolumeDriver": "",
            "VolumesFrom": null,
            "CapAdd": null,
            "CapDrop": null,
            "Dns": [],
            "DnsOptions": [],
            "DnsSearch": [],
            "ExtraHosts": null,
            "GroupAdd": null,
            "IpcMode": "",
            "Cgroup": "",
            "Links": null,
            "OomScoreAdj": 0,
            "PidMode": "",
            "Privileged": false,
            "PublishAllPorts": false,
            "ReadonlyRootfs": false,
            "SecurityOpt": null,
            "UTSMode": "",
            "UsernsMode": "",
            "ShmSize": 67108864,
            "Runtime": "runc",
            "ConsoleSize": [
                0,
                0
            ],
            "Isolation": "",
            "CpuShares": 0,
            "Memory": 0,
            "NanoCpus": 0,
            "CgroupParent": "",
            "BlkioWeight": 0,
            "BlkioWeightDevice": null,
            "BlkioDeviceReadBps": null,
            "BlkioDeviceWriteBps": null,
            "BlkioDeviceReadIOps": null,
            "BlkioDeviceWriteIOps": null,
            "CpuPeriod": 0,
            "CpuQuota": 0,
            "CpuRealtimePeriod": 0,
            "CpuRealtimeRuntime": 0,
            "CpusetCpus": "",
            "CpusetMems": "",
            "Devices": [],
            "DeviceCgroupRules": null,
            "DiskQuota": 0,
            "KernelMemory": 0,
            "MemoryReservation": 0,
            "MemorySwap": 0,
            "MemorySwappiness": -1,
            "OomKillDisable": false,
            "PidsLimit": 0,
            "Ulimits": null,
            "CpuCount": 0,
            "CpuPercent": 0,
            "IOMaximumIOps": 0,
            "IOMaximumBandwidth": 0
        },
        "GraphDriver": {
            "Data": null,
            "Name": "aufs"
        },
        "Mounts": [],
        "Config": {
            "Hostname": "a74c40ecf2bf",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
            ],
            "Cmd": [
                "/bin/bash",
                "-c",
                "while true; do echo hello world; sleep 1;done"
            ],
            "Image": "ubuntu",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": null,
            "OnBuild": null,
            "Labels": {}
        },
        "NetworkSettings": {
            "Bridge": "",
            "SandboxID": "3305cf8f47e8e04015f4276d7ff58b02ee2224981dc932a0a0ec4590e5277c39",
            "HairpinMode": false,
            "LinkLocalIPv6Address": "",
            "LinkLocalIPv6PrefixLen": 0,
            "Ports": {},
            "SandboxKey": "/var/run/docker/netns/3305cf8f47e8",
            "SecondaryIPAddresses": null,
            "SecondaryIPv6Addresses": null,
            "EndpointID": "6c937be3f6e16fb4036316bb508ccb67434ea1a1913c4fc18e56d00872635eea",
            "Gateway": "172.17.0.1",
            "GlobalIPv6Address": "",
            "GlobalIPv6PrefixLen": 0,
            "IPAddress": "172.17.0.2",
            "IPPrefixLen": 16,
            "IPv6Gateway": "",
            "MacAddress": "02:42:ac:11:00:02",
            "Networks": {
                "bridge": {
                    "IPAMConfig": null,
                    "Links": null,
                    "Aliases": null,
                    "NetworkID": "1aaf32710fa4bd4b51a599ebbbe7a6a2827d8fcd46157a3fc4a3f962ff23e511",
                    "EndpointID": "6c937be3f6e16fb4036316bb508ccb67434ea1a1913c4fc18e56d00872635eea",
                    "Gateway": "172.17.0.1",
                    "IPAddress": "172.17.0.2",
                    "IPPrefixLen": 16,
                    "IPv6Gateway": "",
                    "GlobalIPv6Address": "",
                    "GlobalIPv6PrefixLen": 0,
                    "MacAddress": "02:42:ac:11:00:02"
                }
            }
        }
    }
]
root@doushuo-virtual-machine:~# 

此外还可以用-f或者--format标志来标定查看结果:

root@doushuo-virtual-machine:~# docker inspect  -f '{{.NetworkSettings.IPAddress}}' daemon_dave
172.17.0.2
root@doushuo-virtual-machine:~# 

可以指定多个容器,并标定多个输出结果:

root@doushuo-virtual-machine:~# docker inspect  -f '{{.Name}} {{.Args}}' daemon_dave doushuo
/daemon_dave [-c while true; do echo hello world; sleep 1;done]
/doushuo []
root@doushuo-virtual-machine:~# 

使用此命令可以查看容器的大部分配置信息,包括名称、命令、网络配置以及这个容器相关文件的具体路径等。

删除容器

如果容器不再使用,使用docker rm命令来删除:

root@doushuo-virtual-machine:~# docker ps -a 
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS                   PORTS               NAMES
31c2219a7ada        ubuntu              "/bin/sh -c 'while..."   3 hours ago         Exited (2) 3 hours ago                       log_none
c97d942c5b24        ubuntu              "/bin/bash -c 'whi..."   3 hours ago         Exited (1) 3 hours ago                       log_syslog
a74c40ecf2bf        ubuntu              "/bin/bash -c 'whi..."   4 hours ago         Up 3 hours                                   daemon_dave
d3efdb7fc09c        ubuntu              "/bin/bash"              4 hours ago         Up 2 hours                                   doushuo
82a9aa3f8f4d        ubuntu              "/bin/bash"              5 weeks ago         Exited (0) 4 hours ago                       determined_hamilton
root@doushuo-virtual-machine:~# docker rm log_none
log_none
root@doushuo-virtual-machine:~# docker ps -a
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS                   PORTS               NAMES
c97d942c5b24        ubuntu              "/bin/bash -c 'whi..."   3 hours ago         Exited (1) 3 hours ago                       log_syslog
a74c40ecf2bf        ubuntu              "/bin/bash -c 'whi..."   4 hours ago         Up 3 hours                                   daemon_dave
d3efdb7fc09c        ubuntu              "/bin/bash"              4 hours ago         Up 2 hours                                   doushuo
82a9aa3f8f4d        ubuntu              "/bin/bash"              5 weeks ago         Exited (0) 4 hours ago                       determined_hamilton
root@doushuo-virtual-machine:~# 

注意:自docker1.6.2开始,可以通过docker rm -f删除所有包括正在运行的容器;在这之前,如果要删除正在运行的容器,要先使用docker kill或者docker stop命令停止容器,再进行删除操作。
删除所有容器:

root@doushuo-virtual-machine:~# docker ps -a
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS                   PORTS               NAMES
c97d942c5b24        ubuntu              "/bin/bash -c 'whi..."   3 hours ago         Exited (1) 3 hours ago                       log_syslog
a74c40ecf2bf        ubuntu              "/bin/bash -c 'whi..."   4 hours ago         Up 3 hours                                   daemon_dave
d3efdb7fc09c        ubuntu              "/bin/bash"              4 hours ago         Up 2 hours                                   doushuo
82a9aa3f8f4d        ubuntu              "/bin/bash"              5 weeks ago         Exited (0) 4 hours ago                       determined_hamilton
root@doushuo-virtual-machine:~# docker ps -a -q
c97d942c5b24
a74c40ecf2bf
d3efdb7fc09c
82a9aa3f8f4d
root@doushuo-virtual-machine:~# docker rm `docker ps -a -q`
c97d942c5b24
82a9aa3f8f4d
Error response from daemon: You cannot remove a running container a74c40ecf2bf0059739f5db1d3aa7a6b745d88d517f8683ec4bbd6557a459574. Stop the container before attempting removal or force remove
Error response from daemon: You cannot remove a running container d3efdb7fc09cfd37e29c50249a1370701e0b06cd9ccee06dfce362adacb1576a. Stop the container before attempting removal or force remove
root@doushuo-virtual-machine:~# 

docker ps -a列出所有容器,-q标志仅显示容器的ID;传递给docker rm意为删除所有容器。有两个正在运行的容器不能删除,加上-f标志删除所有容器:

root@doushuo-virtual-machine:~# docker rm  -f `docker ps -a -q`
a74c40ecf2bf
d3efdb7fc09c
root@doushuo-virtual-machine:~# docker ps -a
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
root@doushuo-virtual-machine:~# 
    原文作者:dshowing
    原文地址: https://www.jianshu.com/p/440d7477be35
    本文转自网络文章,转载此文章仅为分享知识,如有侵权,请联系博主进行删除。
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