跨主机容器之间的通讯
Flannel
overlay覆盖性网络，不支持路由转发，通过数据etcd数据库保存子网信息以及网络分配信息
给每台主机分配一个网段
通过utp传输数据包
主机名
IP
功能
软件
Node1
192.168.2.2
主控主机
etcd flannel docker
Node2
192.168.2.3
被控主机
flannel docker
Node1
安装etcd
yum - install etcd
安装flannel
yum -y install flannel
配置etcd文件 //修改以下两行
[root@node1 ~]# vim /etc/etcd/etcd.conf
ETCD_LISTEN_CLIENT_URLS="http://0.0.0.0:2379,httpd://0.0.0.0:4001"
ETCD_ADVERTISE_CLIENT_URLS="http://192.168.2.2:2379,http://192.168.2.2:4001" //自己的IP地址
systemctl start etcd.service
systemctl enable etcd.service
etcdctl set testdir/testkey0 1000
etcdctl get testdir/testkey0
[root@node1 ~]# etcdctl set testdir/testkey0 1000
1000
[root@node1 ~]# etcdctl get testdir/testkey0
1000
测试集群健康
[root@node1 ~]# etcdctl -C http://192.168.2.2:4001 cluster-health
member 8e9e05c52164694d is healthy: got healthy result from http://192.168.2.2:2379
cluster is healthy
配置flannel要访问的etcd数据库所在的位置
[root@node1 ~]# vim /etc/sysconfig/flanneld
FLANNEL_ETCD_ENDPOINTS="http://192.168.2.2:2379" //数据库的位置
[root@node1 ~]# etcdctl set b 123
123
[root@node1 ~]# etcdctl get b
123
[root@node1 ~]# etcdctl mk /atomic.io/network/config '{ "Network" : "172.20.0.0/16" }' //指定之后容器ip地址的分配
{ "Network" : "172.20.0.0/16" }
启动flanneld
[root@node1 ~]# systemctl start flanneld.service
[root@node1 ~]# systemctl enable flanneld.service
查看ip地址
[root@node1 ~]# ip a s
inet 172.20.92.0/16 scope global flannel0
下载docker
编写一个脚本docker.sh
Vim docker.sh
br_netfilter
EOF
modprobe overlay
modprobe br_netfilter
cat << EOF | tee /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-iptables = 1
net.bridge.bridge-nf-call-ip6tables = 1
net.ipv4.ip_forward = 1
EOF
sysctl --system
yum install -y yum-utils device-mapper-persistent-data lvm2
yum-config-manager --add-repo https://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo
yum install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin -y
[root@node1 ~]# bash docker.sh
[root@node1 ~]# systemctl start docker.service
查看dockerip
ip a s
5: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
link/ether 02:42:2c:dd:93:f8 brd ff:ff:ff:ff:ff:ff
inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
valid_lft forever preferred_lft forever
查看flannel子网ip
[root@node1 ~]# cat /run/flannel/subnet.env
FLANNEL_NETWORK=172.20.0.0/16
FLANNEL_SUBNET=172.20.92.1/24
FLANNEL_MTU=1472
FLANNEL_IPMASQ=false
配置daemon.json文件
从其他主机复制一份daemon.json
scp root@192.168.2.13:/etc/docker/daemon.json /etc/docker/
[root@node1 ~]# vim /etc/docker/daemon.json
{
"registry-mirrors": [
"https://do.nark.eu.org",
"https://dc.j8.work",
"https://docker.m.daocloud.io",
"https://dockerproxy.com",
"https://docker.mirrors.ustc.edu.cn",
"https://docker.nju.edu.cn"
]
,
"hosts": [
"tcp://0.0.0.0:2375",
"unix:///var/run/docker.sock"
],
"insecure-registries":[
"http://192.168.2.2:5050"
]
}
[root@node1 ~]# vim /usr/lib/systemd/system/docker.service
ExecStart=/usr/bin/dockerd
ExecReload=/bin/kill -s HUP $MAINPID
[root@node1 ~]# systemctl daemon-reload
[root@node1 ~]# systemctl restart docker.service
[root@node1 ~]# cat /run/flannel/subnet.env
FLANNEL_NETWORK=172.20.0.0/16
FLANNEL_SUBNET=172.20.92.1/24
FLANNEL_MTU=1472
FLANNEL_IPMASQ=false
[root@node1 ~]# vim /etc/docker/daemon.json
{
"registry-mirrors": [
"https://do.nark.eu.org",
"https://dc.j8.work",
"https://docker.m.daocloud.io",
"https://dockerproxy.com",
"https://docker.mirrors.ustc.edu.cn",
"https://docker.nju.edu.cn"
]
,
"hosts": [
"tcp://0.0.0.0:2375",
"unix:///var/run/docker.sock"
],
"insecure-registries":[
"http://192.168.2.2:5050"
],
"bip" : "172.20.92.1/24",
"mtu" : 1472
}
[root@node1 ~]# systemctl restart docker.service
iP a s //结果是flannel子网与docker子网保持一致
4: flannel0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1472 qdisc pfifo_fast state UNKNOWN group default qlen 500
link/none
inet 172.20.92.0/16 scope global flannel0
valid_lft forever preferred_lft forever
inet6 fe80::96c7:b4dc:5cc3:f913/64 scope link flags 800
valid_lft forever preferred_lft forever
5: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1472 qdisc noqueue state DOWN group default
link/ether 02:42:2c:dd:93:f8 brd ff:ff:ff:ff:ff:ff
inet 172.20.92.1/24 brd 172.20.92.255 scope global docker0
valid_lft forever preferred_lft forever
[root@node1 ~]# docker pull centos
[root@node1 ~]# docker run -it centos:latest /bin/bash
[root@4a37c9ff2dce /]# [root@node1 ~]#
[root@node1 ~]# docker inspect 4a37|grep IPAdd
"SecondaryIPAddresses": null,
"IPAddress": "172.20.92.2",
"IPAddress": "172.20.92.2",
Node2
安装flannel
Yum -y install flannel
配置flannel要访问的etcd数据库所在的位置
[root@node2 ~]# vim /etc/sysconfig/flanneld
FLANNEL_ETCD_ENDPOINTS="http://192.168.2.2:2379" //node1的IP地址
启动flannel
[root@node2 ~]# systemctl start flanneld.service
查看flannel分配的ip网段
[root@node2 ~]# ip a s
inet 172.20.80.0/16 scope global flannel0
[root@node2 ~]# cat /run/flannel/subnet.env
FLANNEL_NETWORK=172.20.0.0/16
FLANNEL_SUBNET=172.20.80.1/24
FLANNEL_MTU=1472
FLANNEL_IPMASQ=false
将docker.sh文件拉取到node2机器上
scp docker.sh root@192.168.2.3:~
运行这个脚本下载安装docker
source docker.sh
[root@node2 ~]# systemctl start docker.service
将flannel分配网段写入到daemon.json
[root@node2 ~]# scp root@192.168.2.2:/etc/docker/daemon.json /etc/docker/
[root@node2 ~]# vim /etc/docker/daemon.json //只改这两个
"bip" : "172.20.80.1/24",
"mtu" : 1472
[root@node2 ~]# cat /run/flannel/subnet.env
FLANNEL_NETWORK=172.20.0.0/16
FLANNEL_SUBNET=172.20.80.1/24
FLANNEL_MTU=1472
FLANNEL_IPMASQ=false
[root@node2 ~]# systemctl restart docker.service
重启docker如果不能重启，就修改远程管理
[root@node2 ~]# vim /usr/lib/systemd/system/docker.service
ExecStart=/usr/bin/dockerd
ExecReload=/bin/kill -s HUP $MAINPID
重启docker
[root@node2 ~]# systemctl daemon-reload
[root@node2 ~]# systemctl restart docker.service
[root@node2 ~]# ip a s
4: flannel0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1472 qdisc pfifo_fast state UNKNOWN group default qlen 500
link/none
inet 172.20.80.0/16 scope global flannel0
valid_lft forever preferred_lft forever
inet6 fe80::538a:3c3e:6b72:66ad/64 scope link flags 800
valid_lft forever preferred_lft forever
5: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1472 qdisc noqueue state DOWN group default
link/ether 02:42:2f:fa:fe:ce brd ff:ff:ff:ff:ff:ff
inet 172.20.80.1/24 brd 172.20.80.255 scope global docker0
valid_lft forever preferred_lft forever
[root@node2 ~]# docker pull centos
拉取一个centos镜像
Using default tag: latest
latest: Pulling from library/centos
a1d0c7532777: Pull complete
Digest: sha256:a27fd8080b517143cbbbab9dfb7c8571c40d67d534bbdee55bd6c473f432b177
Status: Downloaded newer image for centos:latest
docker.io/library/centos:latest
[root@node2 ~]# docker run -it centos:latest /bin/bash
Ping node1中容器的IP地址
[root@6d5944f42024 /]# ping 172.20.92.1
PING 172.20.92.1 (172.20.92.1) 56(84) bytes of data.
64 bytes from 172.20.92.1: icmp_seq=1 ttl=61 time=2.29 ms
64 bytes from 172.20.92.1: icmp_seq=2 ttl=61 time=1.12 ms
在node1里面ping node2里面的容器的IP地址
[root@node1 ~]# docker attach 4a
[root@4a37c9ff2dce /]# ping 172.20.80.1
PING 172.20.80.1 (172.20.80.1) 56(84) bytes of data.
64 bytes from 172.20.80.1: icmp_seq=1 ttl=61 time=1.26 ms
总结
工作原理：
使用flannel为docker主机（宿主机）分配网段
网段的信息以及ip的信息保存在etcd数据库中
当flannel开始运行的时候，会从etcd数据库中读取{“Network”:”172.20.0.0/16”,随机为当前的主机添加一个flannel0网卡
配置docker下的daemon.json文件，让docker0网卡变成和flannel的网段一致，之后docker下创建的容器的ip就在flannel的网段控制之内
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