【转】docker固定IP第二种方法

默认情况下启动一个container，其会自动获取一个跟docker0同网段的IP，而且重启container其IP一般会发生变化，但有时候我们会需要固定的IP。要实现这个并不困难。

docker run启动一个container的命令有一个--net的参数用于指定container的网络类型

--net="bridge" Set the Network mode for the container      'bridge': creates a new network stack for the container on the docker bridge      'none': no networking for this container      'container:<name|id>': reuses another container network stack      'host': use the host network stack inside the container. Note: the host mode gives the container full access to local system services such as D-bus and is therefore considered insecure.

docker默认使用'bridge'来设置container的网络模式（即从与docker0同网段的未使用的IP中取一个作为container的IP），我们这里使用'none'来实现自己手动配置container的网络。

首先我们以**--net='none'**的方式启动一个container

[yaxin@cube2x ~]$docker run -i -t --rm --net='none' ubuntu /bin/bash root@db84e747c362:/# ifconfig -a lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) root@db84e747c362:/# 

可以看到，由于我们使用'none'模式，container中没有获取到IP，甚至连网卡都没有，下面我们开始给container配置IP

首先获取container的pid（我们需要通过pid获取file descriptor）

[yaxin@cube2x ~]$docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES db84e747c362 docker.cn/docker/ubuntu:latest "/bin/bash" 4 minutes ago Up 4 minutes sharp_kirch [yaxin@cube2x ~]$docker inspect -f "{{.State.Pid}}" sharp_kirch 23090 

ip-netns的man page中有这样一句

By convention a named network namespace is an object at /var/run/netns/NAME that can be opened. The file descriptor resulting from opening/var/run/netns/NAME refers to the specified network namespace

因而我们需要创建一个链接

[yaxin@cube2x ~]$sudo ln -s /proc/23090/ns/net /var/run/netns/23090 

然后创建一对端到端的网卡，将veth_db84e747c3绑定到docker0网桥，并启动。将另一块网卡X放到container内部

[yaxin@cube2x ~]$sudo ip link add veth_db84e747c3 type veth peer name X [yaxin@cube2x ~]$sudo brctl addif docker0 veth_db84e747c3 [yaxin@cube2x ~]$sudo ip link set veth_db84e747c3 up [yaxin@cube2x ~]$sudo ip link set X netns 23090 

这时查看container的IP，会发现多了一个名为X的网卡

root@db84e747c362:/# ifconfig -a X Link encap:Ethernet HWaddr 5a:7e:4d:ba:63:1c BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) root@db84e747c362:/# 

然后对container内部新添加的网卡进行配置（可以通过man ip-netns更详细查看）

[yaxin@cube2x ~]$sudo ip netns exec 23090 ip link set dev X name eth0 [yaxin@cube2x ~]$sudo ip netns exec 23090 ip link set eth0 up [yaxin@cube2x ~]$sudo ip netns exec 23090 ip addr add 172.17.111.10/16 dev eth0 [yaxin@cube2x ~]$sudo ip netns exec 23090 ip route add default via 172.17.42.1 

注意: 指定给container的IP必须跟docker0在同一网段,且给container的网关应该为docker0的IP

最后，写成shell脚本如下:

#!/usr/bin/env bash # filename: bind_addr.sh if [ `id -u` -ne 0 ];then echo '必须使用root权限' exit fi if [ $# != 2 ]; then echo "使用方法: $0 容器名字 IP" exit 1 fi container_name=$1 bind_ip=$2 container_id=`docker inspect -f '{{.Id}}' $container_name 2> /dev/null` if [ ! $container_id ];then echo "容器不存在" exit 2 fi bind_ip=`echo $bind_ip | egrep '^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$'` if [ ! $bind_ip ];then echo "IP地址格式不正确" exit 3 fi container_minid=`echo $container_id | cut -c 1-10` container_netmask=`ip addr show docker0 | grep "inet\b" | awk '{print $2}' | cut -d / -f2` container_gw=`ip addr show docker0 | grep "inet\b" | awk '{print $2}' | cut -d / -f1` bridge_name="veth_$container_minid" container_ip=$bind_ip/$container_netmask pid=`docker inspect -f '{{.State.Pid}}' $container_name 2> /dev/null` if [ ! $pid ];then echo "获取容器$container_name的id失败" exit 4 fi if [ ! -d /var/run/netns ];then mkdir -p /var/run/netns fi ln -sf /proc/$pid/ns/net /var/run/netns/$pid ip link add $bridge_name type veth peer name X brctl addif docker0 $bridge_name ip link set $bridge_name up ip link set X netns $pid ip netns exec $pid ip link set dev X name eth0 ip netns exec $pid ip link set eth0 up ip netns exec $pid ip addr add $container_ip dev eth0 ip netns exec $pid ip route add default via $container_gw