Docker容器技术介绍（一） --- Docker安装和简单使用

容器技术被认为是未来部署软件的主流趋势之一，高性能，轻量级及跨平台是容器技术的主要特征，传统的应用部署过程大概是：下载软件->编译安装->启动软件，比如现在要安装 LNMP 软件，就得先下载Nginx+Mysql+PHP，然后一个个安装，这对于一两台服务器时还能接受，要是面对成千上万的服务器集群，还不得累死吗，有没有办法把这几个软件打包成一个软件一次性安装呢，容器的出现使得很好的解决了这类问题。

什么是容器？

以上是摘自Docker官网的一段话，应该说是比较权威的解释：容器以一种特定的格式来打包软件，这种格式可以各自独立的运行在同一个操作系统之上，不像虚拟机，容器不会捆绑一个完整的操作系统，而仅仅打包软件运行所需要的依赖库和设置。这样可以实现一个高效、轻量级、自给自足的系统，并且可以保证软件总是以相同的方式运行，而不管它被部署在哪里。

从上可知，容器是一种打包应用的方式，可以帮你打包应用中的所有软件和软件所依赖的环境，并且可以实现跨平台部署。相比虚拟机，容器更高效和轻量化，一台服务器运行1000个虚拟机基本是难以想象的，但IBM的服务器据称已经在一台服务器上运行万级的容器。

为什么使用容器？

Docker是什么？ docker是容器领导者。

Docker是世界领先的软件容器平台，在进行多人协作开发时，开发者可以使用Docker来消除所谓“我这里运行是好的”（works on my machine）问题，运维人员使用Docker来并行的运行和管理应用来获得更优计算密度，基于各自独立的容器。企业使用Docker来建立敏捷的交付方式，实现更快的、更安全的和更自信的交付新功能而不管是Linux或Windos服务器。

Docker安装：

Centos 6.x

[root@localhost ~]# yum install epel-release  
[root@localhost ~]# yum install docker-io  
[root@localhost ~]# service docker start  

输入docker version 验证安装是否成功

[root@localhost ~]# docker version  
Client version: 1.7.1  
Client API version: 1.19  
Go version (client): go1.4.2  
Git commit (client): 786b29d/1.7.1  
OS/Arch (client): linux/amd64  
Server version: 1.7.1  
Server API version: 1.19  
Go version (server): go1.4.2  
Git commit (server): 786b29d/1.7.1  
OS/Arch (server): linux/amd64  

Centos 7.x

最新版的Docker需要64位CentOS 7系统，并且分社区版（CE）和企业版（EE），一般选择免费的社区版即可

1.卸载旧版本（如果安装了的话）

[root@localhost ~]# yum remove docker docker-common docker-selinux docker-engine  
Loaded plugins: fastestmirror  
No Match for argument: docker  
No Match for argument: docker-common  
No Match for argument: docker-selinux  
No Match for argument: docker-engine  
No Packages marked for removal  

2.安装

最简单的安装方式是直接 yum install：

[root@localhost ~]# yum install docker  

如果想要安装最新的稳定版，可以使用下面的安装方式：

[root@localhost software]# wget https://download.docker.com/linux/centos/7/x86_64/stable/Packages/docker-ce-17.06.2.ce-1.el7.centos.x86_64.rpm  
[root@localhost software]# ls  
docker-ce-17.06.2.ce-1.el7.centos.x86_64.rpm  
[root@localhost software]# yum install docker-ce-17.06.2.ce-1.el7.centos.x86_64.rpm   

3.启动Docker服务

[root@localhost software]# systemctl start docker  
[root@localhost software]# ps -aux | grep docker  
root     23624  2.0  2.5 434500 25768 ?        Ssl  06:43   0:00 /usr/bin/dockerd  
root     23627  0.1  0.7 263940  7544 ?        Ssl  06:43   0:00 docker-containerd -l unix:///var/run/docker/libcontainerd/docker-containerd.sock --metrics-interval=0 --start-timeout 2m --state-dir /var/run/docker/libcontainerd/containerd --shim docker-containerd-shim --runtime docker-runc  
root     23744  0.0  0.0 112660   972 pts/0    S+   06:43   0:00 grep --color=auto docker  

可以看到Docker在后台启动了两个守护进程：dockerd 和 docker-containerd

Docker的三个基本概念：镜像、容器、仓库

镜像相当于创建容器的一个模具，一个说明书，而容器就是一个实实在在运行的镜像实例，可以用可执行文件和进程来比喻镜像和容器的关系，而仓库就是用来存放镜像的，相当于git仓库，用来存放不同版本的镜像。

 

Docker安装和简单使用

安装运行Nginx

/*docker search 命令可以搜索镜像，默认从官方镜像库hub.docker.com搜索*/

[root@localhost ~]# docker search nginx      
NAME                                                   DESCRIPTION                                     STARS     OFFICIAL   AUTOMATED  
nginx                                                  Official build of Nginx.                        6903      [OK]         
jwilder/nginx-proxy                                    Automated Nginx reverse proxy for docker c...   1130                 [OK]  
richarvey/nginx-php-fpm                                Container running Nginx + PHP-FPM capable ...   446                  [OK]  
jrcs/letsencrypt-nginx-proxy-companion                 LetsEncrypt container to use with nginx as...   227                  [OK]  
kong                                                   Open-source Microservice & API Management ...   115       [OK]         
webdevops/php-nginx                                    Nginx with PHP-FPM                              90                   [OK]  
kitematic/hello-world-nginx                            A light-weight nginx container that demons...   86                     
bitnami/nginx                                          Bitnami nginx Docker Image                      36                   [OK]  
linuxserver/nginx                                      An Nginx container, brought to you by Linu...   24                     
1and1internet/ubuntu-16-nginx-php-phpmyadmin-mysql-5   ubuntu-16-nginx-php-phpmyadmin-mysql-5          16                   [OK]  
tobi312/rpi-nginx                                      NGINX on Raspberry Pi / armhf                   11                   [OK]  
wodby/drupal-nginx                                     Nginx for Drupal                                8                    [OK]  
webdevops/nginx                                        Nginx container                                 8                    [OK]  
.....  

/* pull 镜像 */

[root@localhost software]# docker pull nginx    
latest: Pulling from nginx  
1cb018da208f: Pull complete   
c1a0d2b79b3f: Pull complete   
0aec54b378f5: Pull complete   
b599d18a520b: Pull complete   
a1cfc1b806a4: Pull complete   
c2504687d157: Pull complete   
a00416541f84: Pull complete   
6adf11c406b6: Pull complete   
9daddd1b8b0f: Pull complete   
036477bc0d5a: Pull complete   
Digest: sha256:248f3c1a01b35a098c85b31c356787068b1c1adbbd2f902fb2d6f49b95fd380f  
Status: Downloaded newer image for nginx:latest  

/* 列出本地镜像 */

[root@localhost software]# docker images   
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE  
nginx               latest              da5939581ac8        2 days ago          108MB  

/* 启动一个容器，并把容器中的80端口映射到宿主机的8080端口 -d表示让容器在后台运行 */

[root@localhost software]# docker run -d -p 8080:80 nginx       
9af52c8b4dab91643860a7355acb1f04013ed5fd8d0b313568322f26affa2c40

/* 列出当前正在运行的容器 */

[root@localhost software]# docker ps  
CONTAINER ID        IMAGE               COMMAND                  CREATED              STATUS              PORTS                  NAMES  
9af52c8b4dab        nginx               "nginx -g 'daemon ..."   About a minute ago   Up About a minute   0.0.0.0:8080->80/tcp   xenodochial_volhard

/* 可以看到上面docker ps的信息没有显示全，有的被截断了 可以在命令加上 --no-trunc 参数强制完全显示 */

[root@localhost ~]# docker ps --no-trunc     
CONTAINER ID                                                       IMAGE               COMMAND                    CREATED             STATUS              PORTS                  NAMES  
724db6813f511ade01cb907ec82008a8930e4db0275cbaf36f6c8503a0cec7c9   nginx               "nginx -g 'daemon off;'"   16 seconds ago      Up 15 seconds       0.0.0.0:8080->80/tcp   goofy_morse   

/* 测试nginx是否正常启动 */

[root@localhost software]# curl '127.0.0.1:8080'     
<!DOCTYPE html>  
<html>  
<head>  
<title>Welcome to nginx!</title>  
<style>  
    body {  
        width: 35em;  
        margin: 0 auto;  
        font-family: Tahoma, Verdana, Arial, sans-serif;  
    }  
</style>  
...  

/* 停止容器运行 */

[root@localhost software]# docker stop 9af52c8b4dab        
9af52c8b4dab  
[root@localhost software]# docker ps  
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES

/* -a 参数会列出所有的容器，包括已停止的 */

[root@localhost ~]# docker ps -a   
CONTAINER ID        IMAGE               COMMAND                CREATED             STATUS                     PORTS               NAMES  
724db6813f51        nginx               "nginx -g 'daemon of   5 minutes ago       Exited (0) 6 seconds ago                       goofy_morse   

/* docker rm 删除容器 */

[root@localhost ~]# docker rm 724db6813f51   
724db6813f51  
[root@localhost ~]# docker ps -a  
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES

/* docker rmi 删除镜像 */

[root@localhost ~]# docker images  
REPOSITORY          TAG                 IMAGE ID            CREATED             VIRTUAL SIZE  
ubuntu              14.04               b44ce450cb60        12 days ago         188 MB  
nginx               latest              036477bc0d5a        13 days ago         108.3 MB  
[root@localhost ~]# docker rmi 036477bc0d5a    
Untagged: nginx:latest  
Deleted: 036477bc0d5a32c5618eb350669ebadcf082c41f1be3b0141d22284742bc796f  
Deleted: 9daddd1b8b0faf3af09a3b25704ac2cb742a9a31114c0773c69f745364ac9569  
Deleted: 6adf11c406b68fe96f4e5cbb5f8baf7123f8df13f77cda9d2439e8e3c994fc5b  
Deleted: a00416541f8403247a87f49310e7ae687397bacd613b055a644aafedd4c0cbe1  
Deleted: c2504687d1573cf99eb64283cfa4c160d4e2d15befbd617f5551e5a02242513e  
Deleted: a1cfc1b806a41781e27bef106fb38e49f8d158253d318e032927d507c0285a37  
Deleted: b599d18a520b37f6e0a587485e54dcc141c3a181f25b651fd45d071670b61b72  
Deleted: 0aec54b378f58193513ddf12e1f855d44fb11ccf5810bd93687f6e13d107e8a0  
Deleted: c1a0d2b79b3f6e909c6c621d4e33a3bda0ac46560d18602ca7ff3367360251e7  
Deleted: 1cb018da208f97b77e79f5d42a29a05246afae8f7072683d93e06576af32b470  
[root@localhost ~]# docker images  
REPOSITORY          TAG                 IMAGE ID            CREATED             VIRTUAL SIZE  
ubuntu              14.04               b44ce450cb60        12 days ago         188 MB  

只输入docker可以查看docker支持的所有命令，输入docker COMMAND --help可以查看特定命令的帮助

[root@localhost software]# docker  
  
Usage:  docker COMMAND  
  
A self-sufficient runtime for containers  
  
Options:  
      --config string      Location of client config files (default "/root/.docker")  
  -D, --debug              Enable debug mode  
      --help               Print usage  
  -H, --host list          Daemon socket(s) to connect to  
  -l, --log-level string   Set the logging level ("debug"|"info"|"warn"|"error"|"fatal") (default "info")  
      --tls                Use TLS; implied by --tlsverify  
      --tlscacert string   Trust certs signed only by this CA (default "/root/.docker/ca.pem")  
      --tlscert string     Path to TLS certificate file (default "/root/.docker/cert.pem")  
      --tlskey string      Path to TLS key file (default "/root/.docker/key.pem")  
      --tlsverify          Use TLS and verify the remote  
  -v, --version            Print version information and quit  
  
Management Commands:  
  config      Manage Docker configs  
  container   Manage containers  
  image       Manage images  
  network     Manage networks  
  node        Manage Swarm nodes  
  plugin      Manage plugins  
  secret      Manage Docker secrets  
  service     Manage services  
  stack       Manage Docker stacks  
  swarm       Manage Swarm  
  system      Manage Docker  
  volume      Manage volumes  
  
Commands:  
  attach      Attach local standard input, output, and error streams to a running container  
  build       Build an image from a Dockerfile  
  commit      Create a new image from a container's changes  
  cp          Copy files/folders between a container and the local filesystem  
  create      Create a new container  
  diff        Inspect changes to files or directories on a container's filesystem  
  events      Get real time events from the server  
  exec        Run a command in a running container  
  export      Export a container's filesystem as a tar archive  
  history     Show the history of an image  
  images      List images  
  import      Import the contents from a tarball to create a filesystem image  
  info        Display system-wide information  
  inspect     Return low-level information on Docker objects  
  kill        Kill one or more running containers  
  load        Load an image from a tar archive or STDIN  
  login       Log in to a Docker registry  
  logout      Log out from a Docker registry  
  logs        Fetch the logs of a container  
  pause       Pause all processes within one or more containers  
  port        List port mappings or a specific mapping for the container  
.....  

[root@localhost software]# docker run --help  
  
Usage:  docker run [OPTIONS] IMAGE [COMMAND] [ARG...]  
  
Run a command in a new container  
  
Options:  
      --add-host list                  Add a custom host-to-IP mapping (host:ip)  
  -a, --attach list                    Attach to STDIN, STDOUT or STDERR  
      --blkio-weight uint16            Block IO (relative weight), between 10 and 1000, or 0 to disable (default 0)  
      --blkio-weight-device list       Block IO weight (relative device weight) (default [])  
      --cap-add list                   Add Linux capabilities  
      --cap-drop list                  Drop Linux capabilities  
      --cgroup-parent string           Optional parent cgroup for the container  
      --cidfile string                 Write the container ID to the file  
      --cpu-period int                 Limit CPU CFS (Completely Fair Scheduler) period  
      --cpu-quota int                  Limit CPU CFS (Completely Fair Scheduler) quota  
      --cpu-rt-period int              Limit CPU real-time period in microseconds  
      --cpu-rt-runtime int             Limit CPU real-time runtime in microseconds  
  -c, --cpu-shares int                 CPU shares (relative weight)  
      --cpus decimal                   Number of CPUs  
      --cpuset-cpus string             CPUs in which to allow execution (0-3, 0,1)  
......  

Docker的简单使用就介绍到这里，想更深入了解Docker技术欢迎关注后续文章！

That‘s it ^^