kubernetes-handbook/practice/node-installation.md

# 部署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](http://rootsongjc.github.io/blogs/kubernetes-network-config/)，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。

``` bash
$ 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](http://rootsongjc.github.io/blogs/kubernetes-network-config/)，之前没有配置TLS，现在需要在serivce配置文件中增加TLS配置。

直接使用yum安装flanneld即可。

```shell
yum install -y flannel
```

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

```ini
[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 \
  -etcd-endpoints=${ETCD_ENDPOINTS} \
  -etcd-prefix=${ETCD_PREFIX} \
  $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。

```ini
# Flanneld configuration options  

# etcd url location.  Point this to the server where etcd runs
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
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。

```shell
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"}}'
```

如果你要使用`host-gw`模式，可以直接将vxlan改成`host-gw`即可。

**配置Docker**

Flannel的[文档](https://github.com/coreos/flannel/blob/master/Documentation/running.md)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"
```

**设置docker0网桥的IP地址**

```shell
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
```

**启动docker**

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**

```shell
systemctl daemon-reload
systemctl start flanneld
systemctl status flanneld
```

现在查询etcd中的内容可以看到：

```bash
$etcdctl --endpoints=${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"}}
```

## 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)：

``` bash
$ 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

``` bash
$ 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/local/bin/
```

### 创建 kubelet 的service配置文件

文件位置`/usr/lib/systemd/system/kubelet.service`。

```ini
[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/local/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。

注意：`/var/lib/kubelet`需要手动创建。

``` bash
###
## 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；
+ `—kubeconfig=/etc/kubernetes/kubelet.kubeconfig `中指定的`kubelet.kubeconfig`文件在第一次启动kubelet之前并不存在，请看下文，当通过CSR请求后会自动生成`kubelet.kubeconfig`文件，如果你的节点上已经生成了`~/.kube/config`文件，你可以将该文件拷贝到该路径下，并重命名为`kubelet.kubeconfig`，所有node节点可以共用同一个kubelet.kubeconfig文件，这样新添加的节点就不需要再创建CSR请求就能自动添加到kubernetes集群中。同样，在任意能够访问到kubernetes集群的主机上使用`kubectl —kubeconfig`命令操作集群时，只要使用`~/.kube/config`文件就可以通过权限认证，因为这里面已经有认证信息并认为你是admin用户，对集群拥有所有权限。

完整 unit 见 [kubelet.service](./systemd/kubelet.service)

### 启动kublet

``` bash
$ 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

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

通过 CSR 请求

``` bash
$ 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

``` bash
$ 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
```

注意：假如你更新kubernetes的证书，只要没有更新`token.csv`，当重启kubelet后，该node就会自动加入到kuberentes集群中，而不会重新发送`certificaterequest`，也不需要在master节点上执行`kubectl certificate approve`操作。前提是不要删除node节点上的`/etc/kubernetes/ssl/kubelet*`和`/etc/kubernetes/kubelet.kubeconfig`文件。否则kubelet启动时会提示找不到证书而失败。

## 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`。

```ini
[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/local/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`。

``` bash
###
# 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](./systemd/kube-proxy.service)

### 启动 kube-proxy

``` bash
$ 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。

```bash
$ 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>
```

提示：上面的测试示例中使用的nginx是我的私有镜像仓库中的镜像`sz-pg-oam-docker-hub-001.tendcloud.com/library/nginx:1.9`，大家在测试过程中请换成自己的nginx镜像地址。

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。

![welcome-nginx](http://olz1di9xf.bkt.clouddn.com/kubernetes-installation-test-nginx.png)