K8s-部署flannel网络.05

内容转载自：https://github.com/opsnull/follow-me-install-kubernetes-cluster/blob/master/05.%E9%83%A8%E7%BD%B2flannel%E7%BD%91%E7%BB%9C.md

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05.部署 flannel 网络

kubernetes 要求集群内各节点(包括 master 节点)能通过 Pod 网段互联互通。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）。

flannel 第一次启动时，从 etcd 获取 Pod 网段信息，为本节点分配一个未使用的 /24 段地址，然后创建 flannel.1（也可能是其它名称，如 flannel1 等） 接口。

flannel 将分配的 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。

下载和分发 flanneld 二进制文件

到 https://github.com/coreos/flannel/releases 页面下载最新版本的发布包：

mkdir flannel
wget https://github.com/coreos/flannel/releases/download/v0.10.0/flannel-v0.10.0-linux-amd64.tar.gz
tar -xzvf flannel-v0.10.0-linux-amd64.tar.gz -C flannel

分发 flanneld 二进制文件到集群master，node节点：

source /opt/k8s/bin/environment.sh
MASTER_NODE_IP=(${MASTER_IP[@]} ${NODE_IP[@]})
for master_node_ip in ${MASTER_NODE_IP[@]}
  do
    echo ">>> ${master_node_ip}"
    scp  flannel/{flanneld,mk-docker-opts.sh} k8s@${master_node_ip}:/opt/k8s/bin/
    ssh k8s@${master_node_ip} "chmod +x /opt/k8s/bin/*"
  done

创建 flannel 证书和私钥

flannel 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：

cat > flanneld-csr.json <

• 该证书只会被 kubectl 当做 client 证书使用，所以 hosts 字段为空；

生成证书和私钥：

cfssl gencert -ca=/etc/kubernetes/cert/ca.pem \
  -ca-key=/etc/kubernetes/cert/ca-key.pem \
  -config=/etc/kubernetes/cert/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（master 和 worker）：

source /opt/k8s/bin/environment.sh
MASTER_NODE_IP=(${MASTER_IP[@]} ${NODE_IP[@]} ${ETCD_IP[@]}) 
for master_node_ip in ${MASTER_NODE_IP[@]}
  do
    echo ">>> ${master_node_ip}"
    ssh root@${master_node_ip} "mkdir -p /etc/flanneld/cert && chown -R k8s /etc/flanneld"
    scp flanneld*.pem k8s@${master_node_ip}:/etc/flanneld/cert
  done

向 etcd 写入集群 Pod 网段信息(etcd机器操作)

注意：本步骤只需执行一次。

source /opt/k8s/bin/environment.sh
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 \
  set ${FLANNEL_ETCD_PREFIX}/config '{"Network":"'${CLUSTER_CIDR}'", "SubnetLen": 24, "Backend": {"Type": "vxlan"}}'

• flanneld 当前版本 (v0.10.0) 不支持 etcd v3，故使用 etcd v2 API 写入配置 key 和网段数据；
• 写入的 Pod 网段 ${CLUSTER_CIDR} 必须是 /16 段地址，必须与 kube-controller-manager 的 --cluster-cidr 参数值一致；

创建 flanneld 的 systemd unit 文件

source /opt/k8s/bin/environment.sh
export IFACE=eth0
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} \\
  -iface=${IFACE}
ExecStartPost=/opt/k8s/bin/mk-docker-opts.sh -k DOCKER_NETWORK_OPTIONS -d /run/flannel/docker
Restart=on-failure

[Install]
WantedBy=multi-user.target
RequiredBy=docker.service
EOF

• mk-docker-opts.sh 脚本将分配给 flanneld 的 Pod 子网网段信息写入 /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；
• 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，如上面的 eth0 接口;
• flanneld 运行时需要 root 权限；

分发 flanneld systemd unit 文件到所有节点

source /opt/k8s/bin/environment.sh
MASTER_NODE_IP=(${MASTER_IP[@]} ${NODE_IP[@]}) 
for master_node_ip in ${MASTER_NODE_IP[@]}
  do
    echo ">>> ${master_node_ip}"
    scp flanneld.service root@${master_node_ip}:/etc/systemd/system/
  done

启动 flanneld 服务

source /opt/k8s/bin/environment.sh
MASTER_NODE_IP=(${MASTER_IP[@]} ${NODE_IP[@]}) 
for master_node_ip in ${MASTER_NODE_IP[@]}
  do
    echo ">>> ${master_node_ip}"
    ssh root@${master_node_ip} "systemctl daemon-reload && systemctl enable flanneld && systemctl restart flanneld"
  done

检查启动结果

source /opt/k8s/bin/environment.sh
MASTER_NODE_IP=(${MASTER_IP[@]} ${NODE_IP[@]}) 
for master_node_ip in ${MASTER_NODE_IP[@]}
  do
    echo ">>> ${master_node_ip}"
    ssh k8s@${master_node_ip} "systemctl status flanneld|grep Active"
  done

确保状态为 active (running)，否则查看日志，确认原因：

$ journalctl -u flanneld

检查分配给各 flanneld 的 Pod 网段信息（etcd机器操作）

查看集群 Pod 网段(/16)：

source /opt/k8s/bin/environment.sh
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：

{"Network":"172.30.0.0/16", "SubnetLen": 24, "Backend": {"Type": "vxlan"}}

查看已分配的 Pod 子网段列表(/24):（etcd机器操作）

source /opt/k8s/bin/environment.sh
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：

/kubernetes/network/subnets/172.30.74.0-24
/kubernetes/network/subnets/172.30.21.0-24
/kubernetes/network/subnets/172.30.1.0-24
/kubernetes/network/subnets/172.30.95.0-24
/kubernetes/network/subnets/172.30.43.0-24
/kubernetes/network/subnets/172.30.69.0-24

查看某一 Pod 网段对应的节点 IP 和 flannel 接口地址:（etcd机器操作）

source /opt/k8s/bin/environment.sh
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}/subnets/172.30.69.0-24

输出：

{"PublicIP":"172.27.129.103","BackendType":"vxlan","BackendData":{"VtepMAC":"12:21:93:9e:b1:eb"}}

验证各节点能通过 Pod 网段互通

在各节点上部署 flannel 后，检查是否创建了 flannel 接口(名称可能为 flannel0、flannel.0、flannel.1 等)：

source /opt/k8s/bin/environment.sh
MASTER_NODE_IP=(${MASTER_IP[@]} ${NODE_IP[@]}) 
for master_node_ip in ${MASTER_NODE_IP[@]}
  do
    echo ">>> ${master_node_ip}"
    ssh ${master_node_ip} "/usr/sbin/ip addr show flannel.1|grep -w inet"
  done

输出：

>>> 172.27.129.101
    inet 172.30.95.0/32 scope global flannel.1
>>> 172.27.129.102
    inet 172.30.43.0/32 scope global flannel.1
>>> 172.27.129.103
    inet 172.30.69.0/32 scope global flannel.1
>>> 172.27.129.107
    inet 172.30.74.0/32 scope global flannel.1
>>> 172.27.129.108
    inet 172.30.21.0/32 scope global flannel.1
>>> 172.27.129.109
    inet 172.30.1.0/32 scope global flannel.1

在各节点上 ping 所有 flannel 接口 IP，确保能通：

source /opt/k8s/bin/environment.sh
MASTER_NODE_IP=(${MASTER_IP[@]} ${NODE_IP[@]}) 
for master_node_ip in ${MASTER_NODE_IP[@]}
  do
    echo ">>> ${master_node_ip}"
    ssh ${master_node_ip} "ping -c 1 172.30.95.0"
    ssh ${master_node_ip} "ping -c 1 172.30.43.0"
    ssh ${master_node_ip} "ping -c 1 172.30.69.0"
    ssh ${master_node_ip} "ping -c 1 172.30.74.0"
    ssh ${master_node_ip} "ping -c 1 172.30.21.0"
    ssh ${master_node_ip} "ping -c 1 172.30.1.0"
  done

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