部署 flannel 网络(在master节点上执行）
kubernetes组件kubelet服务依赖docker服务，docker网络需要用flannel来配置docker0网桥的ip地址，所以需要先安装flannel网络组建
flannel 使用 vxlan 技术为各节点创建一个可以互通的 Pod 网络，使用的端口为 UDP 8472（需要开放该端口，如公有云 AWS 等）。
flanneld 第一次启动时，从 etcd 获取配置的 Pod 网段信息，为本节点分配一个未使用的地址段，然后创建 flannedl.1 网络接口（也可能是其它名称，如 flannel1 等）。
flannel 将分配给自己的 Pod 网段信息写入 /run/flannel/docker 文件，docker 后续使用这个文件中的环境变量设置 docker0 网桥，从而从这个地址段为本节点的所有 Pod 容器分配 IP
下载和安装flanneld 二进制文件
cd /opt/k8s/work mkdir flannel wget https://github.com/coreos/flannel/releases/download/v0.11.0/flannel-v0.11.0-linux-amd64.tar.gz tar -xzvf flannel-v0.11.0-linux-amd64.tar.gz -C flannel cp flannel/{flanneld,mk-docker-opts.sh} /opt/k8s/bin/ export node_ip=192.168.0.114 scp flannel/{flanneld,mk-docker-opts.sh} root@${192.168.0.114}:/opt/k8s/bin/创建 flanneld 证书和私钥
flanneld 从 etcd 集群存取网段分配信息，而 etcd 集群启用了双向 x509 证书认证，所以需要为 flanneld 生成证书和私钥。
创建证书签名请求
cd /opt/k8s/work cat > flanneld-csr.json <<EOF { "CN": "flanneld", "hosts": [], "key": { "algo": "rsa", "size": 2048 }, "names": [ { "C": "CN", "ST": "NanJing", "L": "NanJing", "O": "k8s", "OU": "system" } ] } EOF生成证书和私钥
cfssl gencert -ca=/opt/k8s/work/ca.pem -ca-key=/opt/k8s/work/ca-key.pem -config=/opt/k8s/work/ca-config.json -profile=kubernetes flanneld-csr.json | cfssljson -bare flanneld ls flanneld*pem将生成的证书和私钥分发到所有节点
cd /opt/k8s/work mkdir -p /etc/flanneld/cert cp flanneld*.pem /etc/flanneld/cert export node_ip=192.168.0.114 ssh root@${node_ip} "mkdir -p /etc/flanneld/cert" scp flanneld*.pem root@${node_ip}:/etc/flanneld/cert
向 etcd 写入集群 Pod 网段信息
cd /opt/k8s/work export FLANNEL_ETCD_PREFIX="/kubernetes/network" export ETCD_ENDPOINTS="https://192.168.0.107:2379" etcdctl --endpoints=${ETCD_ENDPOINTS} --ca-file=/opt/k8s/work/ca.pem --cert-file=/opt/k8s/work/flanneld.pem --key-file=/opt/k8s/work/flanneld-key.pem mk ${FLANNEL_ETCD_PREFIX}/config '{"Network":"172.30.0.0/16", "SubnetLen": 24, "Backend": {"Type": "vxlan"}}'- 写入的 Pod 网段 Network 网络段对应的数值（如 /16）必须小于 SubnetLen对应的值（如24）
创建 flanneld 服务的启动文件
cd /opt/k8s/work export FLANNEL_ETCD_PREFIX="/kubernetes/network" export ETCD_ENDPOINTS="https://192.168.0.107:2379" cat > flanneld.service << EOF [Unit] Description=Flanneld overlay address etcd agent After=network.target After=network-online.target Wants=network-online.target After=etcd.service Before=docker.service [Service] Type=notify ExecStart=/opt/k8s/bin/flanneld \ -etcd-cafile=/etc/kubernetes/cert/ca.pem \ -etcd-certfile=/etc/flanneld/cert/flanneld.pem \ -etcd-keyfile=/etc/flanneld/cert/flanneld-key.pem \ -etcd-endpoints=${ETCD_ENDPOINTS} \ -etcd-prefix=${FLANNEL_ETCD_PREFIX} \ -ip-masq ExecStartPost=/opt/k8s/bin/mk-docker-opts.sh -k DOCKER_NETWORK_OPTIONS -d /run/flannel/docker Restart=always RestartSec=5 StartLimitInterval=0 [Install] WantedBy=multi-user.target RequiredBy=docker.service EOF- mk-docker-opts.sh 脚本将分配给 flanneld 的 Pod 子网段信息，通过-d参数写入 /run/flannel/docker 文件，后续 docker 启动时使用这个文件中的环境变量配置 docker0 网桥， -k 参数控制生成文件中变量的名称，下面docker启动时会用到这个变量；
- flanneld 使用系统缺省路由所在的接口与其它节点通信，对于有多个网络接口（如内网和公网）的节点，可以用 -iface 参数指定通信接口;
- -ip-masq: flanneld 为访问 Pod 网络外的流量设置 SNAT 规则，同时将传递给 Docker 的变量 --ip-masq（/run/flannel/docker 文件中）设置为 false，这样 Docker 将不再创建 SNAT 规则； Docker 的 --ip-masq 为 true 时，创建的 SNAT 规则比较“暴力”：将所有本节点 Pod 发起的、访问非 docker0 接口的请求做 SNAT，这样访问其他节点 Pod 的请求来源 IP 会被设置为 flannel.1 接口的 IP，导致目的 Pod 看不到真实的来源 Pod IP。 flanneld 创建的 SNAT 规则比较温和，只对访问非 Pod 网段的请求做 SNAT
分发flanneld服务
cd /opt/k8s/work cp flanneld.service /etc/systemd/system/ export node_ip=192.168.0.114 scp flanneld.service root@${node_ip}:/etc/systemd/system/启动flanneld服务
systemctl daemon-reload && systemctl enable flanneld && systemctl restart flanneld ssh root@${node_ip) "systemctl daemon-reload && systemctl enable flanneld && systemctl restart flanneld"检查启动结果
systemctl status flanneld|grep Active export node_ip=192.168.0.114 ssh root@${node_ip} "systemctl status flanneld|grep Active"确保状态为 active (running)，否则查看日志，确认原因
如果出现异常，通过如下命令查看
journalctl -u flanneld
检查分配给各 flanneld 的 Pod 网段信息
export FLANNEL_ETCD_PREFIX="/kubernetes/network" export ETCD_ENDPOINTS="https://192.168.0.107:2379" etcdctl --endpoints=${ETCD_ENDPOINTS} --ca-file=/etc/kubernetes/cert/ca.pem --cert-file=/etc/flanneld/cert/flanneld.pem --key-file=/etc/flanneld/cert/flanneld-key.pem get ${FLANNEL_ETCD_PREFIX}/config输出结果
{"Network":"172.30.0.0/16", "SubnetLen": 24, "Backend": {"Type": "vxlan"}}查看已分配的 Pod 子网段列表
export FLANNEL_ETCD_PREFIX="/kubernetes/network" export ETCD_ENDPOINTS="https://192.168.0.107:2379" etcdctl --endpoints=${ETCD_ENDPOINTS} --ca-file=/etc/kubernetes/cert/ca.pem --cert-file=/etc/flanneld/cert/flanneld.pem --key-file=/etc/flanneld/cert/flanneld-key.pem ls ${FLANNEL_ETCD_PREFIX}/subnets输出结果
/kubernetes/network/subnets/172.30.22.0-24 /kubernetes/network/subnets/172.30.78.0-24检查节点 flannel 网络信息
root@master:/opt/k8s/work# ip addr show 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: enp2s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000 link/ether 04:92:26:13:92:2b brd ff:ff:ff:ff:ff:ff 3: wlp3s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000 link/ether d0:c5:d3:57:73:01 brd ff:ff:ff:ff:ff:ff inet 192.168.0.107/24 brd 192.168.0.255 scope global dynamic noprefixroute wlp3s0 valid_lft 6385sec preferred_lft 6385sec inet6 fe80::1fda:e90a:207a:67e4/64 scope link noprefixroute valid_lft forever preferred_lft forever 4: flannel.1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc noqueue state UNKNOWN group default link/ether 12:cb:66:43:de:36 brd ff:ff:ff:ff:ff:ff inet 172.30.22.0/32 scope global flannel.1 valid_lft forever preferred_lft forever inet6 fe80::10cb:66ff:fe43:de36/64 scope link valid_lft forever preferred_lft forever root@master:/opt/k8s/work# ip route show |grep flannel.1 172.30.78.0/24 via 172.30.78.0 dev flannel.1 onlink验证各节点能通过 Pod 网段互通
root@master:/opt/k8s/work# ip addr show flannel.1 |grep -w inet inet 172.30.22.0/32 scope global flannel.1 root@master:/opt/k8s/work# ssh 192.168.0.114 "/sbin/ip addr show flannel.1|grep -w inet" inet 172.30.78.0/32 scope global flannel.1 root@master:/opt/k8s/work# ping -c 1 172.30.78.0 PING 172.30.78.0 (172.30.78.0) 56(84) bytes of data. 64 bytes from 172.30.78.0: icmp_seq=1 ttl=64 time=80.7 ms --- 172.30.78.0 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 80.707/80.707/80.707/0.000 ms root@master:/opt/k8s/work# ssh 192.168.0.114 "ping -c 1 172.30.22.0" PING 172.30.22.0 (172.30.22.0) 56(84) bytes of data. 64 bytes from 172.30.22.0: icmp_seq=1 ttl=64 time=4.09 ms --- 172.30.22.0 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 4.094/4.094/4.094/0.000 ms生成文件内容，注意DOCKER_NETWORK_OPTIONS的值
root@master:/opt/k8s/work# cat /run/flannel/subnet.env FLANNEL_NETWORK=172.30.0.0/16 FLANNEL_SUBNET=172.30.22.1/24 FLANNEL_MTU=1450 FLANNEL_IPMASQ=true root@master:/opt/k8s/work# cat /run/flannel/docker DOCKER_OPT_BIP="--bip=172.30.22.1/24" DOCKER_OPT_IPMASQ="--ip-masq=false" DOCKER_OPT_MTU="--mtu=1450" DOCKER_NETWORK_OPTIONS=" --bip=172.30.22.1/24 --ip-masq=false --mtu=1450"