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理解Docker(1):Docker安装和基础用法详细介绍

程序员文章站 2022-11-01 14:35:27
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...

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:

1.2 docker 到目前(2016/09/16)为止的版本历史
理解Docker(1):Docker安装和基础用法详细介绍

2. docker 的基本操作

2.1 docker 容器的状态机理解Docker(1):Docker安装和基础用法详细介绍

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    ?     00:00:00   python app.py
root@devstack:/home/sammy# docker logs newweb31 #获取容器的日志
 * running on http://0.0.0.0:5000/ (press ctrl+c to quit)
root@devstack:/home/sammy# docker stop newweb31 #停止容器
newweb31
root@devstack:/home/sammy# docker inspect --format='{{.state.status}}' newweb31
exited
root@devstack:/home/sammy# docker rm newweb31 #删除容器
newweb31
root@devstack:/home/sammy# docker inspect --format='{{.state.status}}' newweb31
error: no such image, container or task: newweb31

(2) docker stop 和 docker kill

在docker stop 命令执行的时候,会先向容器中pid为1的进程发送系统信号 sigterm,然后等待容器中的应用程序终止执行,如果等待时间达到设定的超时时间(默认为 10秒,用户可以指定特定超时时长),会继续发送sigkill的系统信号强行kill掉进程。在容器中的应用程序,可以选择忽略和不处理sigterm信号,不过一旦达到超时时间,程序就会被系统强行kill掉,因为sigkill信号是直接发往系统内核的,应用程序没有机会去处理它。

比如运行 docker stop web5 -t 20 命令后:

2016-09-16t16:01:18.206540853+08:00 container kill b3256ef1400a7f6a6f242e377a77af5e25d3b12237c4ee7c2e9b31a5f6437868 (image=training/webapp, name=web5, signal=15)
2016-09-16t16:01:38.212352224+08:00 container kill b3256ef1400a7f6a6f242e377a77af5e25d3b12237c4ee7c2e9b31a5f6437868 (image=training/webapp, name=web5, signal=9)
2016-09-16t16:01:38.235021315+08:00 container die b3256ef1400a7f6a6f242e377a77af5e25d3b12237c4ee7c2e9b31a5f6437868 (exitcode=137, image=training/webapp, name=web5)

能看到:

  1. 首先 docker 向容器发出 sigterm 信号(signal=15)
  2. 等待20秒 (01:18 到 01:38)
  3. 再发送 sigkill 系统信号 (signal = 9)
  4. 然后容器被杀掉了 (die)

而 docker kill 命令会直接发出sigkill的系统信号,以强行终止容器中程序的运行。运行 docker kill web5 命令后:

2016-09-16t16:06:44.351086471+08:00 container kill b3256ef1400a7f6a6f242e377a77af5e25d3b12237c4ee7c2e9b31a5f6437868 (image=training/webapp, name=web5, signal=9)
2016-09-16t16:06:44.365116100+08:00 container die b3256ef1400a7f6a6f242e377a77af5e25d3b12237c4ee7c2e9b31a5f6437868 (exitcode=137, image=training/webapp, name=web5)
可见直接发出的是 sigkill 信号,容器立马就被杀掉了。

(3)使用 docker cp 在 host 和 container 之间拷贝文件或者目录

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 平台的基本构成理解Docker(1):Docker安装和基础用法详细介绍
docker 平台基本上由三部分组成:

  • 客户端:用户使用 docker 提供的工具(cli 以及 api 等)来构建,上传镜像并发布命令来创建和启动容器
  • docker 主机:从 docker registry 上下载镜像并启动容器
  • docker registry:docker 镜像仓库,用于保存镜像,并提供镜像上传和下载

后面的文章会具体分析。

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持。