外部网络访问容器
在启动容器时，如果不指定对应参数，在容器外部是无法通过网络来访问容器内的网络应用和服务的。
当容器中运行一些网络应用，要让外部访问这些应用时，可以通过-P或-p参数来指定端口映射。当使用-P标记时，Docker会随机映射一个49000~49900的端口至容器内部开放的网络端口。

首先使用centos镜像新建一个容器，然后在该容器中安装httpd服务并启动

[root@localhost ~]# docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
7169e8be6d3e        centos              "/bin/bash"         About an hour ago   Up About an hour                        serene_goldstine
4cd696928bbe        centos              "bash"              About an hour ago   Up About an hour                        cent_testv2
4f5bf6f33f2c        centos              "bash"              About an hour ago   Up About an hour                        gloomy_colden
0a80861145c9        centos              "bash"              About an hour ago   Up About an hour                        mad_carson
fb45150dbc21        centos              "bash"              2 hours ago         Up 2 hours                              cent_testv
3222c7c5c456        centos              "bash"              2 hours ago         Up 2 hours                              sick_albattani
e136b27a8e17        centos              "bash"              2 hours ago         Up 2 hours                              tender_euclid
[root@localhost ~]# docker exec -it 7169 bash
[root@7169e8be6d3e /]# yum install -y httpd
[root@7169e8be6d3e /]# /usr/sbin/httpd
AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using 172.17.0.8. Set the 'ServerName' directive globally to suppress this message
[root@7169e8be6d3e /]# ps aux |grep httpd
root       151  0.2  0.1 221856  3504 ?        Ss   09:18   0:00 /usr/sbin/httpd
apache     152  0.0  0.1 221856  2632 ?        S    09:18   0:00 /usr/sbin/httpd
apache     153  0.0  0.1 221856  2632 ?        S    09:18   0:00 /usr/sbin/httpd
apache     154  0.0  0.1 221856  2632 ?        S    09:18   0:00 /usr/sbin/httpd
apache     155  0.0  0.1 221856  2632 ?        S    09:18   0:00 /usr/sbin/httpd
apache     156  0.0  0.1 221856  2632 ?        S    09:18   0:00 /usr/sbin/httpd
root       158  0.0  0.0   8988   816 ?        S+   09:19   0:00 grep --color=auto httpd
[root@7169e8be6d3e /]# netstat -lnp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp6       0      0 :::80                   :::*                    LISTEN      151/httpd
Active UNIX domain sockets (only servers)
Proto RefCnt Flags       Type       State         I-Node   PID/Program name     Path

再把该容器导成一个新的镜像（centos_with_httpd），然后再使用新镜像创建容器并指定端口映射

[root@7169e8be6d3e /]# exit
[root@localhost ~]# docker commit -m "centos_with_httpd" -a "genesis" 7169e centos_with_httpd:genesis
50611dba3a229ab939d21b0606d6abb4b0a443e077691d96273a0e09fc58d6ad
[root@localhost ~]# docker images
REPOSITORY                   TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
centos_with_httpd            genesis             50611dba3a22        32 seconds ago      335.3 MB
registry                     latest              5c929a8b587a        33 hours ago        33.27 MB
genesis_centos               latest              85bc3a58f134        5 days ago          277.6 MB
192.168.1.179:5000/busybox   latest              9967c5ad88de        12 days ago         1.093 MB
busybox                      latest              9967c5ad88de        12 days ago         1.093 MB
centos-6-x86                 latest              8fca9486a39b        13 days ago         341.3 MB
centos_with_net              latest              3e8ea8607f08        4 weeks ago         294.9 MB
centos                       latest              9baab0af79c4        6 weeks ago         196.7 MB
[root@localhost ~]# docker run -itd -p 5123:80 centos_with_httpd:genesis bash
c7ffadc832916e12fedb16afc4edd4dfc6e9e38d8cda7333ffac72f7b0da19ee

• -p 可以指定端口映射，本例中将容器的80端口映射为本地的5123端口

[root@localhost ~]# docker exec -it c7ffa bash
[root@c7ffadc83291 /]# netstat -lnp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
Active UNIX domain sockets (only servers)
Proto RefCnt Flags       Type       State         I-Node   PID/Program name     Path
[root@c7ffadc83291 /]# /usr/sbin/httpd
AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using 172.17.0.9. Set the 'ServerName' directive globally to suppress this message
[root@c7ffadc83291 /]# ps aux |grep httpd
root        30  0.0  0.1 221856  3508 ?        Ss   09:27   0:00 /usr/sbin/httpd
apache      31  0.0  0.1 221856  2632 ?        S    09:27   0:00 /usr/sbin/httpd
apache      32  0.0  0.1 221856  2632 ?        S    09:27   0:00 /usr/sbin/httpd
apache      33  0.0  0.1 221856  2632 ?        S    09:27   0:00 /usr/sbin/httpd
apache      34  0.0  0.1 221856  2632 ?        S    09:27   0:00 /usr/sbin/httpd
apache      35  0.0  0.1 221856  2632 ?        S    09:27   0:00 /usr/sbin/httpd
root        37  0.0  0.0   8988   816 ?        S+   09:28   0:00 grep --color=auto httpd
[root@c7ffadc83291 /]# curl localhost
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"><html><head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8"><title>Apache HTTP Server Test Page powered by CentOS</title><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><!-- Bootstrap --><link href="/noindex/css/bootstrap.min.css" rel="stylesheet"><link rel="stylesheet" href="noindex/css/open-sans.css" type="text/css" /><style type="text/css"><!--body {font-family: "Open Sans", Helvetica, sans-serif;font-weight: 100;color: #ccc;background: rgba(10, 24, 55, 1);font-size: 16px;
}h2, h3, h4 {font-weight: 200;
}h2 {font-size: 28px;
}.jumbotron {margin-bottom: 0;color: #333;background: rgb(212,212,221); /* Old browsers */background: radial-gradient(ellipse at center top, rgba(255,255,255,1) 0%,rgba(174,174,183,1) 100%); /* W3C */
}.jumbotron h1 {font-size: 128px;font-weight: 700;color: white;text-shadow: 0px 2px 0px #abc,0px 4px 10px rgba(0,0,0,0.15),0px 5px 2px rgba(0,0,0,0.1),0px 6px 30px rgba(0,0,0,0.1);
}.jumbotron p {font-size: 28px;font-weight: 100;
}.main {background: white;color: #234;border-top: 1px solid rgba(0,0,0,0.12);padding-top: 30px;padding-bottom: 40px;
}.footer {border-top: 1px solid rgba(255,255,255,0.2);padding-top: 30px;
}--></style>
</head>
<body><div class="jumbotron text-center"><div class="container"><h1>Testing 123..</h1><p class="lead">This page is used to test the proper operation of the <a href="http://apache.org">Apache HTTP server</a> after it has been installed. If you can read this page it means that this site is working properly. This server is powered by <a href="http://centos.org">CentOS</a>.</p></div></div><div class="main"><div class="container"><div class="row"><div class="col-sm-6"><h2>Just visiting?</h2><p class="lead">The website you just visited is either experiencing problems or is undergoing routine maintenance.</p><p>If you would like to let the administrators of this website know that you've seen this page instead of the page you expected, you should send them e-mail. In general, mail sent to the name "webmaster" and directed to the website's domain should reach the appropriate person.</p><p>For example, if you experienced problems while visiting www.example.com, you should send e-mail to "webmaster@example.com".</p></div><div class="col-sm-6"><h2>Are you the Administrator?</h2><p>You should add your website content to the directory <tt>/var/www/html/</tt>.</p><p>To prevent this page from ever being used, follow the instructions in the file <tt>/etc/httpd/conf.d/welcome.conf</tt>.</p><h2>Promoting Apache and CentOS</h2><p>You are free to use the images below on Apache and CentOS Linux powered HTTP servers.  Thanks for using Apache and CentOS!</p><p><a href="http://httpd.apache.org/"><img src="data:images/apache_pb.gif" alt="[ Powered by Apache ]"></a> <a href="http://www.centos.org/"><img src="data:images/poweredby.png" alt="[ Powered by CentOS Linux ]" height="31" width="88"></a></p></div></div></div></div></div><div class="footer"><div class="container"><div class="row"><div class="col-sm-6"><h2>Important note:</h2><p class="lead">The CentOS Project has nothing to do with this website or its content,it just provides the software that makes the website run.</p><p>If you have issues with the content of this site, contact the owner of the domain, not the CentOS project.Unless you intended to visit CentOS.org, the CentOS Project does not have anything to do with this website,the content or the lack of it.</p><p>For example, if this website is www.example.com, you would find the owner of the example.com domain at the following WHOIS server:</p><p><a href="http://www.internic.net/whois.html">http://www.internic.net/whois.html</a></p></div><div class="col-sm-6"><h2>The CentOS Project</h2><p>The CentOS Linux distribution is a stable, predictable, manageable and reproduceable platform derived fromthe sources of Red Hat Enterprise Linux (RHEL).<p><p>Additionally to being a popular choice for web hosting, CentOS also provides a rich platform for open source communities to build upon. For more informationplease visit the <a href="http://www.centos.org/">CentOS website</a>.</p></div></div></div></div></div>
</body></html>
[root@c7ffadc83291 /]# vi /var/www/html/1.html

写入ginesis2011.github.io，保存退出（内容可以随意填写）

[root@c7ffadc83291 /]# curl localhost/1.html
ginesis2011.github.io
[root@c7ffadc83291 /]# exit
[root@localhost ~]# curl 192.168.1.179:5123/1.html
ginesis2011.github.io

• 注：192.168.1.179为宿主机IP

[root@localhost ~]# docker ps
CONTAINER ID        IMAGE                       COMMAND             CREATED             STATUS              PORTS                  NAMES
c7ffadc83291        centos_with_httpd:genesis   "bash"              8 minutes ago       Up 8 minutes        0.0.0.0:5123->80/tcp   furious_banach
7169e8be6d3e        centos                      "/bin/bash"         About an hour ago   Up About an hour                           serene_goldstine
4cd696928bbe        centos                      "bash"              About an hour ago   Up About an hour                           cent_testv2
4f5bf6f33f2c        centos                      "bash"              2 hours ago         Up 2 hours                                 gloomy_colden
0a80861145c9        centos                      "bash"              2 hours ago         Up 2 hours                                 mad_carson
fb45150dbc21        centos                      "bash"              2 hours ago         Up 2 hours                                 cent_testv
3222c7c5c456        centos                      "bash"              3 hours ago         Up 3 hours                                 sick_albattani
e136b27a8e17        centos                      "bash"              3 hours ago         Up 3 hours                                 tender_euclid