docker自带了EXPOSE命令，可以通过编写dockerfile加-p参数方便的映射container内部端口，但是对于已经运行的container，如果你想对外开放一个新的端口，只能编辑dockerfile然后重新build，有点不太方便。
其实docker本身使用了iptables来做端口映射的，所以我们可以通过一些简单的操作来实现动态映射运行中的container端口。
通过运行iptables命令可以看到具体的端口映射(下面的实例中IP为192.168.42.41的container开放了22和20280等端口)
[yaxin@ubox ~]$sudo iptables -nvxL
Chain INPUT (policy ACCEPT 262 packets, 529689 bytes)
pkts bytes target prot opt in out source destination
14355 789552 DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:25
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
5479459 653248187 DOCKER all -- * docker0 0.0.0.0/0 0.0.0.0/0
93990 314970368 ACCEPT all -- * docker0 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
4705395 2183219154 ACCEPT all -- docker0 !docker0 0.0.0.0/0 0.0.0.0/0
0 0 ACCEPT all -- docker0 docker0 0.0.0.0/0 0.0.0.0/0
Chain OUTPUT (policy ACCEPT 282 packets, 622495 bytes)
pkts bytes target prot opt in out source destination
Chain DOCKER (1 references)
pkts bytes target prot opt in out source destination
218 13193 ACCEPT tcp -- !docker0 docker0 0.0.0.0/0 192.168.42.41 tcp dpt:22280
4868186 297463902 ACCEPT tcp -- !docker0 docker0 0.0.0.0/0 192.168.42.41 tcp dpt:20280
78663 13128102 ACCEPT tcp -- !docker0 docker0 0.0.0.0/0 192.168.42.41 tcp dpt:22
47 4321 ACCEPT tcp -- !docker0 docker0 0.0.0.0/0 192.168.42.41 tcp dpt:28159
[yaxin@ubox ~]$sudo iptables -t nat -nvxL
Chain PREROUTING (policy ACCEPT 210199 packets, 14035875 bytes)
pkts bytes target prot opt in out source destination
1219483 82563968 DOCKER all -- * * 0.0.0.0/0 0.0.0.0/0 ADDRTYPE match dst-type LOCAL
Chain INPUT (policy ACCEPT 197679 packets, 13316595 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 271553 packets, 16671466 bytes)
pkts bytes target prot opt in out source destination
1643 99251 DOCKER all -- * * 0.0.0.0/0 !127.0.0.0/8 ADDRTYPE match dst-type LOCAL
Chain POSTROUTING (policy ACCEPT 271743 packets, 16682594 bytes)
pkts bytes target prot opt in out source destination
13468 811013 MASQUERADE all -- * !docker0 192.168.42.0/24 0.0.0.0/0
0 0 MASQUERADE tcp -- * * 192.168.42.41 192.168.42.41 tcp dpt:22280
0 0 MASQUERADE tcp -- * * 192.168.42.41 192.168.42.41 tcp dpt:20280
0 0 MASQUERADE tcp -- * * 192.168.42.41 192.168.42.41 tcp dpt:22
0 0 MASQUERADE tcp -- * * 192.168.42.41 192.168.42.41 tcp dpt:28159
Chain DOCKER (2 references)
pkts bytes target prot opt in out source destination
22 1404 DNAT tcp -- !docker0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:22280 to:192.168.42.41:22280
288 17156 DNAT tcp -- !docker0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:20280 to:192.168.42.41:20280
93 5952 DNAT tcp -- !docker0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:22222 to:192.168.42.41:22
8 512 DNAT tcp -- !docker0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:28159 to:192.168.42.41:28159
我们要做的就是根据自己container的情况配置iptables规则。
首先是filter这个表，我们要配置其放通转发，docker默认已经将所有的FORWARD规则放到了DOCKER这个自建链(chain)中了，这样方便配置，也方便查看。
然后再配置nat表为其配置DNAT，这个才是端口转发的核心配置。这个表中只需要配置POSTROUTING和DOCKER链即可，这里不讲为什么这么配置，如果想要深入了解iptables请google一下。
下面举个例子：
假如我有一个container，名字为nginx(通过运行docker ps命令即可查询)，现在我在docker内部运行nginx程序，监听了8888端口，我希望外网可以通过8899端口(注意一下端口)访问
找到docker为nginx分配的IP
[yaxin@ubox ~]$sudo docker inspect -f '{{.NetworkSettings.IPAddress}}' nginx
192.168.42.43
配置iptables中filter表的FORWARD(DOCKER)链
[yaxin@ubox ~]$sudo iptables -A DOCKER ! -i docker0 -o docker0 -p tcp --dport 8888 -d 192.168.42.43 -j ACCEPT
配置iptables中nat表的PREROUTING(DOCKER)和POSTROUTING链
[yaxin@ubox ~]$sudo iptables -t nat -A POSTROUTING -p tcp --dport 8888 -s 192.168.42.43 -d 192.168.42.43 -j MASQUERADE
[yaxin@ubox ~]$sudo iptables -t nat -A DOCKER ! -i dokcer0 -p tcp --dport 8899 -j DNAT --to-destination 192.168.42.43:8888
通过外网访问curl http://IP:8899就会显示nginx下配置的html页面
最后iptables规则
[yaxin@ubox ~]$sudo iptables -nvxL
Chain INPUT (policy ACCEPT 67893 packets, 212661547 bytes)
pkts bytes target prot opt in out source destination
14364 790008 DROP tcp -- * * 0.0.0.0/0 0.0.0.0/0 tcp dpt:25
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
5479682 653269356 DOCKER all -- * docker0 0.0.0.0/0 0.0.0.0/0
94186 314986910 ACCEPT all -- * docker0 0.0.0.0/0 0.0.0.0/0 ctstate RELATED,ESTABLISHED
4705658 2183254076 ACCEPT all -- docker0 !docker0 0.0.0.0/0 0.0.0.0/0
0 0 ACCEPT all -- docker0 docker0 0.0.0.0/0 0.0.0.0/0
Chain OUTPUT (policy ACCEPT 71253 packets, 222512872 bytes)
pkts bytes target prot opt in out source destination
Chain DOCKER (1 references)
pkts bytes target prot opt in out source destination
218 13193 ACCEPT tcp -- !docker0 docker0 0.0.0.0/0 192.168.42.41 tcp dpt:22280
4868186 297463902 ACCEPT tcp -- !docker0 docker0 0.0.0.0/0 192.168.42.41 tcp dpt:20280
78663 13128102 ACCEPT tcp -- !docker0 docker0 0.0.0.0/0 192.168.42.41 tcp dpt:22
47 4321 ACCEPT tcp -- !docker0 docker0 0.0.0.0/0 192.168.42.41 tcp dpt:28159
27 4627 ACCEPT tcp -- !docker0 docker0 0.0.0.0/0 192.168.42.43 tcp dpt:8888
[yaxin@ubox ~]$sudo iptables -t nat -nvxL
Chain PREROUTING (policy ACCEPT 232 packets, 16606 bytes)
pkts bytes target prot opt in out source destination
1220281 82620790 DOCKER all -- * * 0.0.0.0/0 0.0.0.0/0 ADDRTYPE match dst-type LOCAL
Chain INPUT (policy ACCEPT 216 packets, 15671 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 317 packets, 19159 bytes)
pkts bytes target prot opt in out source destination
1644 99311 DOCKER all -- * * 0.0.0.0/0 !127.0.0.0/8 ADDRTYPE match dst-type LOCAL
Chain POSTROUTING (policy ACCEPT 321 packets, 19367 bytes)
pkts bytes target prot opt in out source destination
13512 813656 MASQUERADE all -- * !docker0 192.168.42.0/24 0.0.0.0/0
0 0 MASQUERADE tcp -- * * 192.168.42.41 192.168.42.41 tcp dpt:22280
0 0 MASQUERADE tcp -- * * 192.168.42.41 192.168.42.41 tcp dpt:20280
0 0 MASQUERADE tcp -- * * 192.168.42.41 192.168.42.41 tcp dpt:22
0 0 MASQUERADE tcp -- * * 192.168.42.41 192.168.42.41 tcp dpt:28159
0 0 MASQUERADE tcp -- * * 192.168.42.43 192.168.42.43 tcp dpt:8888
Chain DOCKER (2 references)
pkts bytes target prot opt in out source destination
22 1404 DNAT tcp -- !docker0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:22280 to:192.168.42.41:22280
288 17156 DNAT tcp -- !docker0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:20280 to:192.168.42.41:20280
93 5952 DNAT tcp -- !docker0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:22222 to:192.168.42.41:22
8 512 DNAT tcp -- !docker0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:28159 to:192.168.42.41:28159
4 208 DNAT tcp -- !dokcer0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:8899 to:192.168.42.43:8888
当然，使用手动配置也是比较麻烦的，所以我写了一个脚本来自动配置端口映射，使用方法脚本中有说明
#!/bin/bash
# filename: docker_expose.sh
if [ `id -u` -ne 0 ];then
echo "[EROOR] Please use root to run this script"
exit 23
fi
if [ $# -ne 3 ];then
echo "Usage: $0 <container_name> <add|del> [[<machine_ip>:]<machine_port>:]<container_port>[/<protocol_type>]"
exit 1
fi
IPV4_RE='(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])'
container_name=$1
action=$2
arguments=$3
# check action
if [ "$action"x != "add"x -a "$action"x != "del"x ];then
echo "[ERROR] Please use add or del parameter to add port map or delete port map"
exit 654
fi
if [ "$action"x == "add"x ];then
action="A"
else
action="D"
fi
# get container ip by container name
container_ip=`docker inspect -f '{{.NetworkSettings.IPAddress}}' $container_name 2> /dev/null`
if [ -z $container_ip ];then
echo "[ERROR] Get container's (${container_name}) IP error, please ensure you have this container"
exit 2
fi
# parse arguments
protocol_type=`echo $arguments | awk -F '/' '{print $2}'`
if [ -z $protocol_type ];then
protocol_type="tcp"
fi
# check protocol
if [ "$protocol_type"x != "tcp"x -a "$protocol_type"x != "udp"x ];then
echo "[ERROR] Only tcp or udp protocol is allowed"
exit 99
fi
machine_ip=''
machine_port=''
container_port=''
# split the left arguments
arguments=${arguments%/*}
machine_ip=`echo $arguments | awk -F ':' '{print $1}'`
machine_port=`echo $arguments | awk -F ':' '{print $2}'`
container_port=`echo $arguments | awk -F ':' '{print $3}'`
if [ -z $machine_port ];then
# arguments is: 234
container_port=$machine_ip
machine_port=$machine_ip
unset machine_ip
elif [ -z $container_port ];then
# arguments is: 234:456
container_port=$machine_ip
machine_port=$machine_port
unset machine_ip
fi
# check port number function
_check_port_number() {
local port_num=$1
if ! echo $port_num | egrep "^[0-9]+$" &> /dev/null;then
echo "[ERROR] Invalid port number $port_num"
exit 3
fi
if [ $port_num -gt 65535 -o $port_num -lt 1 ];then
echo "[ERROR] Port number $port_num is out of range(1-56635)"
exit 4
fi
}
# check port and ip address
_check_port_number $container_port
_check_port_number $machine_port
if [ ! -z $machine_ip ];then
if ! echo $machine_ip | egrep "^${IPV4_RE}$" &> /dev/null;then
echo "[ERROR] Invalid Ip Adress $machine_ip"
exit 5
fi
# check which interface bind the IP
for interface in `ifconfig -s | sed -n '2,$p' | awk '{print $1}'`;do
interface_ip=`ifconfig $interface | awk '/inet addr/{print substr($2,6)}'`
if [ "$interface_ip"x == "$machine_ip"x ];then
interface_name=$interface
break
fi
done
if [ -z $interface_name ];then
echo "[ERROR] Can not find interface bind with $machine_ip"
exit 98
fi
fi
# run iptables command
echo "[INFO] Now start to change rules to iptables"
echo "[INFO] Changing POSTROUTING chain of nat table"
iptables -t nat -${action} POSTROUTING -p ${protocol_type} --dport ${container_port} -s ${container_ip} -d ${container_ip} -j MASQUERADE
if [ -z $interface_name ];then
echo "[INFO] Changing DOCKER chain of filter table"
iptables -${action} DOCKER ! -i docker0 -o docker0 -p ${protocol_type} --dport ${container_port} -d ${container_ip} -j ACCEPT
echo "[INFO] Changing DOCKER chain of nat table"
iptables -t nat -${action} DOCKER ! -i docker0 -p ${protocol_type} --dport ${machine_port} -j DNAT --to-destination ${container_ip}:${container_port}
else
echo "[INFO] Changing DOCKER chain of filter table"
iptables -${action} DOCKER -i $interface_name -o docker0 -p ${protocol_type} --dport ${container_port} -d ${container_ip} -j ACCEPT
echo "[INFO] Changing DOCKER chain of nat table"
iptables -t nat -${action} DOCKER -i $interface_name -p ${protocol_type} --dport ${machine_port} -j DNAT --to-destination ${container_ip}:${container_port}
fi
来源： http://yaxin-cn.github.io/Docker/expose-port-of-running-docker-container.html
