理解Docker（1）：Docker安装和基础用法详细介绍

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Docker是一个用了一种新颖方式实现的超轻量虚拟机，在实现的原理和应用上还是和VM有巨大差别，专业的叫法是应用容器（Application Container）。（我个人还是喜欢称虚拟机）

1. 安装

1.1 在 Ubuntu 14.04 上安装 Docker

前提要求：

内核版本必须是3.10或者以上

依次执行下面的步骤：

sudo apt-get update
sudo apt-get install apt-transport-https ca-certificates
sudo apt-key adv --keyserver hkp://p80.pool.sks-keyservers.net:80 --recv-keys 58118E89F3A912897C070ADBF76221572C52609D
编辑 /etc/apt/sources.list.d/docker.list 文件，添加 deb https://apt.dockerproject.org/repo ubuntu-trusty main
sudo apt-get update
sudo apt-get purge lxc-docker
apt-cache policy docker-engine
apt-get upgrade
sudo apt-get install linux-image-extra-$(uname -r) linux-image-extra-virtual
sudo apt-get install docker-engine

至此，安装过程完成。

运行 sudo service docker start 启动 Docker 守护进程。

运行 docker version 查看 Docker 版本

root@devstack:/home/sammy# docker --version
Docker version 1.12.1, build 23cf638

启动第一个容器：

启动第一个Docker 容器 docker run hello-world

root@devstack:/home/sammy# docker run hello-world

Hello from Docker!
This message shows that your installation appears to be working correctly.

它的运行成功也表明前面的安装步骤都运行正确了。

以上内容参考自 Docker 官网：https://docs.docker.com/engine/installation/linux/ubuntulinux/

1.2 Docker 到目前（2016/09/16）为止的版本历史

2. Docker 的基本操作

2.1 Docker 容器的状态机

一个容器在某个时刻可能处于以下几种状态之一：

created：已经被创建（使用 docker ps -a 命令可以列出）但是还没有被启动（使用 docker ps 命令还无法列出）
running：运行中
paused：容器的进程被暂停了
restarting：容器的进程正在重启过程中
exited：上图中的 stopped 状态，表示容器之前运行过但是现在处于停止状态（要区别于 created 状态，它是指一个新创出的尚未运行过的容器）。可以通过 start 命令使其重新进入 running 状态
destroyed：容器被删除了，再也不存在了

你可以在 docker inspect 命令的输出中查看其详细状态：

"State": {
   "Status": "running",
   "Running": true,
   "Paused": false,
   "Restarting": false,
   "OOMKilled": false,
   "Dead": false,
   "Pid": 4597,
   "ExitCode": 0,
   "Error": "",
   "StartedAt": "2016-09-16T08:09:34.53403504Z",
   "FinishedAt": "2016-09-16T08:06:44.365106765Z"
  }

2.2 Docker 命令概述

我们可以把Docker 的命令大概地分类如下：

镜像操作：
 build  Build an image from a Dockerfile
 commit Create a new image from a container's changes
 images List images
 load  Load an image from a tar archive or STDIN
 pull  Pull an image or a repository from a registry
 push  Push an image or a repository to a registry
 rmi  Remove one or more images
 search Search the Docker Hub for images
 tag  Tag an image into a repository
 save  Save one or more images to a tar archive (streamed to STDOUT by default)
 history 显示某镜像的历史
 inspect 获取镜像的详细信息

 容器及其中应用的生命周期操作：
 create Create a new container （创建一个容器）  
 kill  Kill one or more running containers
 inspect Return low-level information on a container, image or task
 pause  Pause all processes within one or more containers
 ps  List containers
 rm  Remove one or more containers （删除一个或者多个容器）
 rename Rename a container
 restart Restart a container
 run  Run a command in a new container （创建并启动一个容器）
 start  Start one or more stopped containers （启动一个处于停止状态的容器）
 stats  Display a live stream of container(s) resource usage statistics （显示容器实时的资源消耗信息）
 stop  Stop one or more running containers （停止一个处于运行状态的容器）
 top  Display the running processes of a container
 unpause Unpause all processes within one or more containers
 update Update configuration of one or more containers
 wait  Block until a container stops, then print its exit code
 attach Attach to a running container
 exec  Run a command in a running container
 port  List port mappings or a specific mapping for the container
 logs  获取容器的日志 
 
 容器文件系统操作：
 cp  Copy files/folders between a container and the local filesystem
 diff  Inspect changes on a container's filesystem
 export Export a container's filesystem as a tar archive
 import Import the contents from a tarball to create a filesystem image
 
 Docker registry 操作：
 login  Log in to a Docker registry.
 logout Log out from a Docker registry.
 
 Volume 操作
 volume Manage Docker volumes
 
 网络操作
 network Manage Docker networks
 
 Swarm 相关操作
 swarm  Manage Docker Swarm
 service Manage Docker services
 node  Manage Docker Swarm nodes  
 
 系统操作： 
 version Show the Docker version information
 events Get real time events from the server (持续返回docker 事件)
 info  Display system-wide information （显示Docker 主机系统范围内的信息）

比较有意思的几个命令：

（1）容器从生到死整个生命周期

root@devstack:/home/sammy# docker create --name web31 training/webapp python app.py #创建名字为 web31 的容器 7465f4cb7c49555af32929bd1bc4213f5e72643c0116450e495b71c7ec128502 root@devstack:/home/sammy# docker inspect --format='{{.State.Status}}' web31 #其状态为 created created root@devstack:/home/sammy# docker start web31 #启动容器 web31 root@devstack:/home/sammy# docker inspect --format='{{.State.Status}}' web31 #其状态为 running running root@devstack:/home/sammy# docker pause web31 #暂停容器 web31 root@devstack:/home/sammy# docker inspect --format='{{.State.Status}}' web31 paused root@devstack:/home/sammy# docker unpause web31 #继续容器 web31 root@devstack:/home/sammy# docker inspect --format='{{.State.Status}}' web31 running root@devstack:/home/sammy# docker rename web31 newweb31 #重命名 root@devstack:/home/sammy# docker inspect --format='{{.State.Status}}' newweb31 running root@devstack:/home/sammy# docker top newweb31 #在容器中运行 top 命令 UID PID PPID C STIME TTY TIME CMD root 5009 4979 0 16:28 "htmlcode">

root@devstack:/home/sammy# docker cp /home/sammy/mydockerbuild/Dockerfile web5:/webapp #从 host 拷贝文件到 container 里面
root@devstack:/home/sammy#
root@devstack:/home/sammy# docker cp web5:/webapp/Dockerfile /home/sammy/Dockerfile #从 container 里面拷贝文件到 host 上
root@devstack:/home/sammy# ls /home/sammy
chroot devstack Dockerfile mongodbdocker mydockerbuild webapp

（4）docker export 和 import

docker export：将一个容器的文件系统打包为一个压缩文件

root@devstack:/home/sammy# docker export web5 -o ./web5
root@devstack:/home/sammy# ls
chroot devstack Dockerfile mongodbdocker mydockerbuild web5 webapp

docker import：从一个压缩文件创建一个镜像

root@devstack:/home/sammy# docker import web5 web5img -m "imported on 0916"
sha256:745bb258be0a69a517367667646148bb2f662565bb3d222b50c0c22e5274a926
root@devstack:/home/sammy# docker history web5img
IMAGE    CREATED    CREATED BY   SIZE    COMMENT
745bb258be0a  6 seconds ago       324 MB    imported on 0916

2.3 docker run 命令

docker run 命令会创建一个容器并启动它，它也是包含很多的参数，按照用途将它们分类如下：

cgroups 和 namespace 相关：
  --blkio-weight value   Block IO (relative weight), between 10 and 1000
  --blkio-weight-device value Block IO weight (relative device weight) (default [])
  --cgroup-parent string  Optional parent cgroup for the container
  --cpu-percent int    CPU percent (Windows only)
  --cpu-period int    Limit CPU CFS (Completely Fair Scheduler) period
  --cpu-quota int    Limit CPU CFS (Completely Fair Scheduler) quota
 -c, --cpu-shares int    CPU shares (relative weight)
  --cpuset-cpus string   CPUs in which to allow execution (0-3, 0,1)
  --cpuset-mems string   MEMs in which to allow execution (0-3, 0,1)
  --device-read-bps value  Limit read rate (bytes per second) from a device (default [])
  --device-read-iops value  Limit read rate (IO per second) from a device (default [])
  --device-write-bps value  Limit write rate (bytes per second) to a device (default [])
  --device-write-iops value  Limit write rate (IO per second) to a device (default [])
  --ipc string     IPC namespace to use
 -m, --memory string    Memory limit
  --memory-reservation string Memory soft limit
  --memory-swap string   Swap limit equal to memory plus swap: '-1' to enable unlimited swap
  --memory-swappiness int  Tune container memory swappiness (0 to 100) (default -1)
  --kernel-memory string  Kernel memory limit
 -u, --user string     Username or UID (format: <name|uid>[:<group|gid>])
  --userns string    User namespace to use
  --uts string     UTS namespace to use
 -h, --hostname string    Container host name
  --pid string     PID namespace to use
  --pids-limit int    Tune container pids limit (set -1 for unlimited)
  --isolation string   Container isolation technology
  --io-maxbandwidth string  Maximum IO bandwidth limit for the system drive (Windows only)
  --io-maxiops uint    Maximum IOps limit for the system drive (Windows only)
 
 linux process capabilities 相关参数：
  --cap-add value    Add Linux capabilities (default [])
  --cap-drop value    Drop Linux capabilities (default [])
 
 容器运行模式和环境相关：
 -d, --detach      Run container in background and print container ID
 -e, --env value     Set environment variables (default [])
  --env-file value    Read in a file of environment variables (default [])
 
 DNS 相关：
  --dns value     Set custom DNS servers (default [])
  --dns-opt value    Set DNS options (default [])
  --dns-search value   Set custom DNS search domains (default [])
 
 健康检查相关：
  --health-cmd string   Command to run to check health
  --health-interval duration Time between running the check
  --health-retries int   Consecutive failures needed to report unhealthy
  --health-timeout duration  Maximum time to allow one check to run
  --no-healthcheck    Disable any container-specified HEALTHCHECK
  
 IP 和端口：
  --ip string     Container IPv4 address (e.g. 172.30.100.104)
  --ip6 string     Container IPv6 address (e.g. 2001:db8::33)
 -p, --publish value    Publish a container's port(s) to the host (default [])
 -P, --publish-all     Publish all exposed ports to random ports
  --expose value    Expose a port or a range of ports (default [])
  --mac-address string   Container MAC address (e.g. 92:d0:c6:0a:29:33)
  --add-host value    Add a custom host-to-IP mapping (host:ip) (default [])
  
 Volume 相关：
 -v, --volume value    Bind mount a volume (default [])
  --volume-driver string  Optional volume driver for the container
  --volumes-from value   Mount volumes from the specified container(s) (default [])
  --storage-opt value   Storage driver options for the container (default [])
 
 Network 有关：
  --network string    Connect a container to a network (default "default")
  --network-alias value   Add network-scoped alias for the container (default [])
  --link value     Add link to another container (default [])
  --link-local-ip value   Container IPv4/IPv6 link-local addresses (default [])
 
 日志有关：
  --log-driver string   Logging driver for the container
  --log-opt value    Log driver options (default [])
 
 交互性有关：
 -a, --attach value    Attach to STDIN, STDOUT or STDERR (default [])
 -i, --interactive     Keep STDIN open even if not attached
 
 OOM 有关： 
  --oom-kill-disable   Disable OOM Killer
  --oom-score-adj int   Tune host's OOM preferences (-1000 to 1000)
 
 其它（待更进一步分类）：
  --cidfile string    Write the container ID to the file
  --detach-keys string   Override the key sequence for detaching a container
  --device value    Add a host device to the container (default [])
  --disable-content-trust  Skip image verification (default true)
  --entrypoint string   Overwrite the default ENTRYPOINT of the image
  --group-add value    Add additional groups to join (default [])
  --help      Print usage
 -l, --label value     Set meta data on a container (default [])
  --label-file value   Read in a line delimited file of labels (default [])
  --name string     Assign a name to the container
  --privileged     Give extended privileges to this container
  --read-only     Mount the container's root filesystem as read only
  --restart string    Restart policy to apply when a container exits (default "no")
  --rm       Automatically remove the container when it exits
  --runtime string    Runtime to use for this container
  --security-opt value   Security Options (default [])
  --shm-size string    Size of /dev/shm, default value is 64MB
  --sig-proxy     Proxy received signals to the process (default true)
  --stop-signal string   Signal to stop a container, SIGTERM by default (default "SIGTERM")
  --sysctl value    Sysctl options (default map[])
  --tmpfs value     Mount a tmpfs directory (default [])
 -t, --tty       Allocate a pseudo-TTY
  --ulimit value    Ulimit options (default [])
 -w, --workdir string    Working directory inside the container

具体的内容以后会有专门文件分析。

3. Doker 平台的基本构成
Docker 平台基本上由三部分组成：