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部署kubernetes node节点

kubernetes node 节点包含如下组件：

• Flanneld：参考我之前写的文章Kubernetes基于Flannel的网络配置，之前没有配置TLS，现在需要在serivce配置文件中增加TLS配置。
• Docker1.12.5：docker的安装很简单，这里也不说了。
• kubelet
• kube-proxy

下面着重讲kubelet和kube-proxy的安装，同时还要将之前安装的flannel集成TLS验证。

目录和文件

我们再检查一下三个节点上，经过前几步操作生成的配置文件。

$ ls /etc/kubernetes/ssl
admin-key.pem  admin.pem  ca-key.pem  ca.pem  kube-proxy-key.pem  kube-proxy.pem  kubernetes-key.pem  kubernetes.pem
$ ls /etc/kubernetes/
apiserver  bootstrap.kubeconfig  config  controller-manager  kubelet  kube-proxy.kubeconfig  proxy  scheduler  ssl  token.csv

配置Flanneld

参考我之前写的文章Kubernetes基于Flannel的网络配置，之前没有配置TLS，现在需要在serivce配置文件中增加TLS配置。

service配置文件/usr/lib/systemd/system/flanneld.service。

[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
EnvironmentFile=/etc/sysconfig/flanneld
EnvironmentFile=-/etc/sysconfig/docker-network
ExecStart=/usr/bin/flanneld-start $FLANNEL_OPTIONS
ExecStartPost=/usr/libexec/flannel/mk-docker-opts.sh -k DOCKER_NETWORK_OPTIONS -d /run/flannel/docker
Restart=on-failure

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

/etc/sysconfig/flanneld配置文件。

# Flanneld configuration options  

# etcd url location.  Point this to the server where etcd runs
FLANNEL_ETCD_ENDPOINTS="https://172.20.0.113:2379,https://172.20.0.114:2379,https://172.20.0.115:2379"

# etcd config key.  This is the configuration key that flannel queries
# For address range assignment
FLANNEL_ETCD_PREFIX="/kube-centos/network"

# Any additional options that you want to pass
FLANNEL_OPTIONS="-etcd-cafile=/etc/kubernetes/ssl/ca.pem -etcd-certfile=/etc/kubernetes/ssl/kubernetes.pem -etcd-keyfile=/etc/kubernetes/ssl/kubernetes-key.pem"

在FLANNEL_OPTIONS中增加TLS的配置。

在etcd中创建网络配置

执行下面的命令为docker分配IP地址段。

etcdctl --endpoints=https://172.20.0.113:2379,https://172.20.0.114:2379,https://172.20.0.115:2379 \
  --ca-file=/etc/kubernetes/ssl/ca.pem \
  --cert-file=/etc/kubernetes/ssl/kubernetes.pem \
  --key-file=/etc/kubernetes/ssl/kubernetes-key.pem \
  mkdir /kube-centos/network
etcdctl --endpoints=https://172.20.0.113:2379,https://172.20.0.114:2379,https://172.20.0.115:2379 \
  --ca-file=/etc/kubernetes/ssl/ca.pem \
  --cert-file=/etc/kubernetes/ssl/kubernetes.pem \
  --key-file=/etc/kubernetes/ssl/kubernetes-key.pem \
  mk /kube-centos/network/config "{ \"Network\": \"172.30.0.0/16\", \"SubnetLen\": 24, \"Backend\": { \"Type\": \"vxlan\" } }"

注意：vxlan的性能损耗大约是40%～50%，如果将Type设置为host-gw，网络性能损耗只有10%左右，而配置没有什么不同，只是要保证kubernetes的所有node都在同一个二层网络中。

配置Docker

Flannel的文档中有写Docker Integration：

Docker daemon accepts --bip argument to configure the subnet of the docker0 bridge. It also accepts --mtu to set the MTU for docker0 and veth devices that it will be creating. Since flannel writes out the acquired subnet and MTU values into a file, the script starting Docker can source in the values and pass them to Docker daemon:

source /run/flannel/subnet.env
docker daemon --bip=${FLANNEL_SUBNET} --mtu=${FLANNEL_MTU} &

Systemd users can use EnvironmentFile directive in the .service file to pull in /run/flannel/subnet.env

如果你不是使用yum安装的flanneld，那么需要下载flannel github release中的tar包，解压后会获得一个mk-docker-opts.sh文件。

这个文件是用来Generate Docker daemon options based on flannel env file。

执行./mk-docker-opts.sh -i将会生成如下两个文件环境变量文件。

/run/flannel/subnet.env

FLANNEL_NETWORK=172.30.0.0/16
FLANNEL_SUBNET=172.30.46.1/24
FLANNEL_MTU=1450
FLANNEL_IPMASQ=false

/run/docker_opts.env

DOCKER_OPT_BIP="--bip=172.30.46.1/24"
DOCKER_OPT_IPMASQ="--ip-masq=true"
DOCKER_OPT_MTU="--mtu=1450"

现在查询etcd中的内容可以看到：

$etcdctl --endpoints=${ETCD_ENDPOINTS} \
  --ca-file=/etc/kubernetes/ssl/ca.pem \
  --cert-file=/etc/kubernetes/ssl/kubernetes.pem \
  --key-file=/etc/kubernetes/ssl/kubernetes-key.pem \
  ls /kube-centos/network/subnets
/kube-centos/network/subnets/172.30.14.0-24
/kube-centos/network/subnets/172.30.38.0-24
/kube-centos/network/subnets/172.30.46.0-24
$etcdctl --endpoints=${ETCD_ENDPOINTS} \
  --ca-file=/etc/kubernetes/ssl/ca.pem \
  --cert-file=/etc/kubernetes/ssl/kubernetes.pem \
  --key-file=/etc/kubernetes/ssl/kubernetes-key.pem \
  get /kube-centos/network/config
{ "Network": "172.30.0.0/16", "SubnetLen": 24, "Backend": { "Type": "vxlan" } }
$etcdctl get /kube-centos/network/subnets/172.30.14.0-24
{"PublicIP":"172.20.0.114","BackendType":"vxlan","BackendData":{"VtepMAC":"56:27:7d:1c:08:22"}}
$etcdctl get /kube-centos/network/subnets/172.30.38.0-24
{"PublicIP":"172.20.0.115","BackendType":"vxlan","BackendData":{"VtepMAC":"12:82:83:59:cf:b8"}}
$etcdctl get /kube-centos/network/subnets/172.30.46.0-24
{"PublicIP":"172.20.0.113","BackendType":"vxlan","BackendData":{"VtepMAC":"e6:b2:fd:f6:66:96"}}

设置docker0网桥的IP地址

source /run/flannel/subnet.env
ifconfig docker0 $FLANNEL_SUBNET

这样docker0和flannel网桥会在同一个子网中，如

6: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN 
    link/ether 02:42:da:bf:83:a2 brd ff:ff:ff:ff:ff:ff
    inet 172.30.38.1/24 brd 172.30.38.255 scope global docker0
       valid_lft forever preferred_lft forever
7: flannel.1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc noqueue state UNKNOWN 
    link/ether 9a:29:46:61:03:44 brd ff:ff:ff:ff:ff:ff
    inet 172.30.38.0/32 scope global flannel.1
       valid_lft forever preferred_lft forever

现在就可以重启docker了。

重启了docker后还要重启kubelet，这时又遇到问题，kubelet启动失败。报错：

Mar 31 16:44:41 sz-pg-oam-docker-test-002.tendcloud.com kubelet[81047]: error: failed to run Kubelet: failed to create kubelet: misconfiguration: kubelet cgroup driver: "cgroupfs" is different from docker cgroup driver: "systemd"

这是kubelet与docker的cgroup driver不一致导致的，kubelet启动的时候有个—cgroup-driver参数可以指定为"cgroupfs"或者“systemd”。

--cgroup-driver string                                    Driver that the kubelet uses to manipulate cgroups on the host.  Possible values: 'cgroupfs', 'systemd' (default "cgroupfs")

启动flannel

systemctl daemon-reload
systemctl start flanneld
systemctl status flanneld

安装和配置 kubelet

kubelet 启动时向 kube-apiserver 发送 TLS bootstrapping 请求，需要先将 bootstrap token 文件中的 kubelet-bootstrap 用户赋予 system:node-bootstrapper cluster 角色(role)， 然后 kubelet 才能有权限创建认证请求(certificate signing requests)：

$ cd /etc/kubernetes
$ kubectl create clusterrolebinding kubelet-bootstrap \
  --clusterrole=system:node-bootstrapper \
  --user=kubelet-bootstrap

• --user=kubelet-bootstrap 是在 /etc/kubernetes/token.csv 文件中指定的用户名，同时也写入了/etc/kubernetes/bootstrap.kubeconfig 文件；

下载最新的 kubelet 和 kube-proxy 二进制文件

$ wget https://dl.k8s.io/v1.6.0/kubernetes-server-linux-amd64.tar.gz
$ tar -xzvf kubernetes-server-linux-amd64.tar.gz
$ cd kubernetes
$ tar -xzvf  kubernetes-src.tar.gz
$ cp -r ./server/bin/{kube-proxy,kubelet} /usr/bin/

创建 kubelet 的service配置文件

文件位置/usr/lib/systemd/system/kubelet.serivce。

[Unit]
Description=Kubernetes Kubelet Server
Documentation=https://github.com/GoogleCloudPlatform/kubernetes
After=docker.service
Requires=docker.service

[Service]
WorkingDirectory=/var/lib/kubelet
EnvironmentFile=-/etc/kubernetes/config
EnvironmentFile=-/etc/kubernetes/kubelet
ExecStart=/usr/bin/kubelet \
            $KUBE_LOGTOSTDERR \
            $KUBE_LOG_LEVEL \
            $KUBELET_API_SERVER \
            $KUBELET_ADDRESS \
            $KUBELET_PORT \
            $KUBELET_HOSTNAME \
            $KUBE_ALLOW_PRIV \
            $KUBELET_POD_INFRA_CONTAINER \
            $KUBELET_ARGS
Restart=on-failure

[Install]
WantedBy=multi-user.target

kubelet的配置文件/etc/kubernetes/kubelet。其中的IP地址更改为你的每台node节点的IP地址。

###
## kubernetes kubelet (minion) config
#
## The address for the info server to serve on (set to 0.0.0.0 or "" for all interfaces)
KUBELET_ADDRESS="--address=172.20.0.113"
#
## The port for the info server to serve on
#KUBELET_PORT="--port=10250"
#
## You may leave this blank to use the actual hostname
KUBELET_HOSTNAME="--hostname-override=172.20.0.113"
#
## location of the api-server
KUBELET_API_SERVER="--api-servers=http://172.20.0.113:8080"
#
## pod infrastructure container
KUBELET_POD_INFRA_CONTAINER="--pod-infra-container-image=sz-pg-oam-docker-hub-001.tendcloud.com/library/pod-infrastructure:rhel7"
#
## Add your own!
KUBELET_ARGS="--cgroup-driver=systemd --cluster-dns=10.254.0.2 --experimental-bootstrap-kubeconfig=/etc/kubernetes/bootstrap.kubeconfig --kubeconfig=/etc/kubernetes/kubelet.kubeconfig --require-kubeconfig --cert-dir=/etc/kubernetes/ssl --cluster-domain=cluster.local. --hairpin-mode promiscuous-bridge --serialize-image-pulls=false"

• --address 不能设置为 127.0.0.1，否则后续 Pods 访问 kubelet 的 API 接口时会失败，因为 Pods 访问的 127.0.0.1 指向自己而不是 kubelet；
• 如果设置了 --hostname-override 选项，则 kube-proxy 也需要设置该选项，否则会出现找不到 Node 的情况；
• --experimental-bootstrap-kubeconfig 指向 bootstrap kubeconfig 文件，kubelet 使用该文件中的用户名和 token 向 kube-apiserver 发送 TLS Bootstrapping 请求；
• 管理员通过了 CSR 请求后，kubelet 自动在 --cert-dir 目录创建证书和私钥文件(kubelet-client.crt 和 kubelet-client.key)，然后写入 --kubeconfig 文件；
• 建议在 --kubeconfig 配置文件中指定 kube-apiserver 地址，如果未指定 --api-servers 选项，则必须指定 --require-kubeconfig 选项后才从配置文件中读取 kube-apiserver 的地址，否则 kubelet 启动后将找不到 kube-apiserver (日志中提示未找到 API Server），kubectl get nodes 不会返回对应的 Node 信息;
• --cluster-dns 指定 kubedns 的 Service IP(可以先分配，后续创建 kubedns 服务时指定该 IP)，--cluster-domain 指定域名后缀，这两个参数同时指定后才会生效；

完整 unit 见 kubelet.service

启动kublet

$ systemctl daemon-reload
$ systemctl enable kubelet
$ systemctl start kubelet
$ systemctl status kubelet

通过 kublet 的 TLS 证书请求

kubelet 首次启动时向 kube-apiserver 发送证书签名请求，必须通过后 kubernetes 系统才会将该 Node 加入到集群。

查看未授权的 CSR 请求

$ kubectl get csr
NAME        AGE       REQUESTOR           CONDITION
csr-2b308   4m        kubelet-bootstrap   Pending
$ kubectl get nodes
No resources found.

通过 CSR 请求

$ kubectl certificate approve csr-2b308
certificatesigningrequest "csr-2b308" approved
$ kubectl get nodes
NAME        STATUS    AGE       VERSION
10.64.3.7   Ready     49m       v1.6.1

自动生成了 kubelet kubeconfig 文件和公私钥

$ ls -l /etc/kubernetes/kubelet.kubeconfig
-rw------- 1 root root 2284 Apr  7 02:07 /etc/kubernetes/kubelet.kubeconfig
$ ls -l /etc/kubernetes/ssl/kubelet*
-rw-r--r-- 1 root root 1046 Apr  7 02:07 /etc/kubernetes/ssl/kubelet-client.crt
-rw------- 1 root root  227 Apr  7 02:04 /etc/kubernetes/ssl/kubelet-client.key
-rw-r--r-- 1 root root 1103 Apr  7 02:07 /etc/kubernetes/ssl/kubelet.crt
-rw------- 1 root root 1675 Apr  7 02:07 /etc/kubernetes/ssl/kubelet.key

配置 kube-proxy

创建 kube-proxy 的service配置文件

文件路径/usr/lib/systemd/system/kube-proxy.service。

[Unit]
Description=Kubernetes Kube-Proxy Server
Documentation=https://github.com/GoogleCloudPlatform/kubernetes
After=network.target

[Service]
EnvironmentFile=-/etc/kubernetes/config
EnvironmentFile=-/etc/kubernetes/proxy
ExecStart=/usr/bin/kube-proxy \
	    $KUBE_LOGTOSTDERR \
	    $KUBE_LOG_LEVEL \
	    $KUBE_MASTER \
	    $KUBE_PROXY_ARGS
Restart=on-failure
LimitNOFILE=65536

[Install]
WantedBy=multi-user.target

kube-proxy配置文件/etc/kubernetes/proxy。

###
# kubernetes proxy config

# default config should be adequate

# Add your own!
KUBE_PROXY_ARGS="--bind-address=172.20.0.113 --hostname-override=172.20.0.113 --kubeconfig=/etc/kubernetes/kube-proxy.kubeconfig --cluster-cidr=10.254.0.0/16"

• --hostname-override 参数值必须与 kubelet 的值一致，否则 kube-proxy 启动后会找不到该 Node，从而不会创建任何 iptables 规则；
• kube-proxy 根据 --cluster-cidr 判断集群内部和外部流量，指定 --cluster-cidr 或 --masquerade-all 选项后 kube-proxy 才会对访问 Service IP 的请求做 SNAT；
• --kubeconfig 指定的配置文件嵌入了 kube-apiserver 的地址、用户名、证书、秘钥等请求和认证信息；
• 预定义的 RoleBinding cluster-admin 将User system:kube-proxy 与 Role system:node-proxier 绑定，该 Role 授予了调用 kube-apiserver Proxy 相关 API 的权限；

完整 unit 见 kube-proxy.service

启动 kube-proxy

$ systemctl daemon-reload
$ systemctl enable kube-proxy
$ systemctl start kube-proxy
$ systemctl status kube-proxy

验证测试

我们创建一个niginx的service试一下集群是否可用。

$ kubectl run nginx --replicas=2 --labels="run=load-balancer-example" --image=sz-pg-oam-docker-hub-001.tendcloud.com/library/nginx:1.9  --port=80
deployment "nginx" created
$ kubectl expose deployment nginx --type=NodePort --name=example-service
service "example-service" exposed
$ kubectl describe svc example-service
Name:			example-service
Namespace:		default
Labels:			run=load-balancer-example
Annotations:		<none>
Selector:		run=load-balancer-example
Type:			NodePort
IP:			10.254.62.207
Port:			<unset>	80/TCP
NodePort:		<unset>	32724/TCP
Endpoints:		172.30.60.2:80,172.30.94.2:80
Session Affinity:	None
Events:			<none>
$ curl "10.254.62.207:80"
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>

访问172.20.0.113:32724或172.20.0.114:32724或者172.20.0.115:32724都可以得到nginx的页面。