tags: flanneld
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。
flaneel 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 flannedl.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。
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 二进制文件到集群所有节点:
source /opt/k8s/bin/environment.sh
for node_ip in ${NODE_IPS[@]}
do
echo ">>> ${node_ip}"
scp flannel/{flanneld,mk-docker-opts.sh} k8s@${node_ip}:/opt/k8s/bin/
ssh k8s@${node_ip} "chmod +x /opt/k8s/bin/*"
done
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 <<EOF
{
"CN": "flanneld",
"hosts": [],
"key": {
"algo": "rsa",
"size": 2048
},
"names": [
{
"C": "CN",
"ST": "BeiJing",
"L": "BeiJing",
"O": "k8s",
"OU": "4Paradigm"
}
]
}
EOF
- 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
for node_ip in ${NODE_IPS[@]}
do
echo ">>> ${node_ip}"
ssh root@${node_ip} "mkdir -p /etc/flanneld/cert && chown -R k8s /etc/flanneld"
scp flanneld*.pem k8s@${node_ip}:/etc/flanneld/cert
done
注意:本步骤只需执行一次。
source /opt/k8s/bin/environment.sh
etcdctl \
--endpoints=${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 ${CLUSTER_CIDR} 必须是 /16 段地址,必须与 kube-controller-manager 的
--cluster-cidr
参数值一致;
source /opt/k8s/bin/environment.sh
export IFACE=eth0
cat > flanneld.service << EOF
[Unit]
Description=Flanneld overlay address etcd agent
After=network.target
After=network-online.target
Wants=network-online.target
After=etcd.service
Before=docker.service
[Service]
Type=notify
ExecStart=/opt/k8s/bin/flanneld \\
-etcd-cafile=/etc/kubernetes/cert/ca.pem \\
-etcd-certfile=/etc/flanneld/cert/flanneld.pem \\
-etcd-keyfile=/etc/flanneld/cert/flanneld-key.pem \\
-etcd-endpoints=${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;
完整 unit 见 flanneld.service
source /opt/k8s/bin/environment.sh
for node_ip in ${NODE_IPS[@]}
do
echo ">>> ${node_ip}"
scp flanneld.service root@${node_ip}:/etc/systemd/system/
done
source /opt/k8s/bin/environment.sh
for node_ip in ${NODE_IPS[@]}
do
echo ">>> ${node_ip}"
ssh root@${node_ip} "systemctl daemon-reload && systemctl enable flanneld && systemctl restart flanneld"
done
source /opt/k8s/bin/environment.sh
for node_ip in ${NODE_IPS[@]}
do
echo ">>> ${node_ip}"
ssh k8s@${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
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 ${FLANNEL_ETCD_PREFIX}/config
输出:
{"Network":"172.30.0.0/16", "SubnetLen": 24, "Backend": {"Type": "vxlan"}}
查看已分配的 Pod 子网段列表(/24):
source /opt/k8s/bin/environment.sh
etcdctl \
--endpoints=${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 ${FLANNEL_ETCD_PREFIX}/subnets
输出:
/kubernetes/network/subnets/172.30.81.0-24
/kubernetes/network/subnets/172.30.29.0-24
/kubernetes/network/subnets/172.30.39.0-24
查看某一 Pod 网段对应的节点 IP 和 flannel 接口地址:
source /opt/k8s/bin/environment.sh
etcdctl \
--endpoints=${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/172.30.81.0-24
输出:
{"PublicIP":"172.27.129.105","BackendType":"vxlan","BackendData":{"VtepMAC":"12:21:93:9e:b1:eb"}}
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
for node_ip in ${NODE_IPS[@]}
do
echo ">>> ${node_ip}"
ssh ${node_ip} "/usr/sbin/ip addr show flannel.1|grep -w inet"
done
输出:
inet 172.30.81.0/32 scope global flannel.1
inet 172.30.29.0/32 scope global flannel.1
inet 172.30.39.0/32 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
for node_ip in ${NODE_IPS[@]}
do
echo ">>> ${node_ip}"
ssh ${node_ip} "ping -c 1 172.30.81.0"
ssh ${node_ip} "ping -c 1 172.30.29.0"
ssh ${node_ip} "ping -c 1 172.30.39.0"
done