Kubelet组件运行在Node节点上，维持运行中的Pods以及提供kuberntes运行时环境，主要完成以下使命：
１．监视分配给该Node节点的pods
２．挂载pod所需要的volumes
３．下载pod的secret
４．通过docker/rkt来运行pod中的容器
５．周期的执行pod中为容器定义的liveness探针
６．上报pod的状态给系统的其他组件
７．上报Node的状态
kubelet安装在node节点，我们的node跟apiserver在一起，这里安装在hdss7-21,22上：
首先，kubernetes依赖pause，我们先将此服务上传到们自己的docker私有仓库：
kubernetes中的pause容器主要为每个业务容器提供以下功能：
- 在pod中担任Linux命名空间共享的基础；
- 启用pid命名空间，开启init进程。
1 HDSS7-200上:
# docker pull kubernetes/pause
# docker tag f9d5de079539 harbor.od.com/public/pause:latest
# docker push harbor.od.com/public/pause:latest
首先在hdss7-200上申请证书：
# vi /opt/certs/kubelet-csr.json
{ "CN": "k8s-kubelet", "hosts": [ "127.0.0.1", "192.168.12.10", "192.168.12.21", "192.168.12.22", "192.168.12.23", "192.168.12.24", "192.168.12.25", "192.168.12.26", "192.168.12.27", "192.168.12.28" ], "key": { "algo": "rsa", "size": 2048 }, "names": [ { "C": "CN", "ST": "beijing", "L": "beijing", "O": "od", "OU": "ops" } ]
申请证书：
# cfssl gencert -ca=ca.pem -ca-key=ca-key.pem -config=ca-config.json -profile=server kubelet-csr.json | cfssl-json -bare kubelet
2 拷贝证书到21，22上：
# cd /opt/kubernetes/server/bin/cert/
# scp hdss7-200:/opt/certs/kubelet.pem ./
# scp hdss7-200:/opt/certs/kubelet-key.pem ./
进入到conf目录执行以下命令：21，22上执行：
cert]# cd ../conf/
# kubectl config set-cluster myk8s \
--certificate-authority=/opt/kubernetes/server/bin/cert/ca.pem \
--embed-certs=true \
--server=https://192.168.12.10:7443 \
--kubeconfig=kubelet.kubeconfig
# kubectl config set-credentials k8s-node \
--client-certificate=/opt/kubernetes/server/bin/cert/client.pem \
--client-key=/opt/kubernetes/server/bin/cert/client-key.pem \
--embed-certs=true \
--kubeconfig=kubelet.kubeconfig
# kubectl config set-context myk8s-context \
--cluster=myk8s \
--user=k8s-node \
--kubeconfig=kubelet.kubeconfig
# kubectl config use-context myk8s-context --kubeconfig=kubelet.kubeconfig
hdss7-21上执行：PS：因为不论在哪个节点创建，已经同步到etcd上。
conf]# vi k8s-node.yaml
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
name: k8s-node
roleRef:
apiGroup: rbac.authorization.k8s.io
kind: ClusterRole
name: system:node
subjects:
- apiGroup: rbac.authorization.k8s.io
kind: User
name: k8s-node
# kubectl create -f k8s-node.yaml
检查k8s-node资源创建状态：
# kubectl get clusterrolebinding k8s-node -o yaml
编辑kubelet启动脚本：标红部分第二台要修改成对应的主机名
# vi /opt/kubernetes/server/bin/kubelet.sh
#!/bin/sh
./kubelet \
--anonymous-auth=false \
--cgroup-driver systemd \
--cluster-dns 192.168.0.2 \
--cluster-domain cluster.local \
--runtime-cgroups=/systemd/system.slice \
--kubelet-cgroups=/systemd/system.slice \
--fail-swap-on="false" \
--client-ca-file ./cert/ca.pem \
--tls-cert-file ./cert/kubelet.pem \
--tls-private-key-file ./cert/kubelet-key.pem \
--hostname-override hdss7-21.host.com \
--image-gc-high-threshold 20 \
--image-gc-low-threshold 10 \
--kubeconfig ./conf/kubelet.kubeconfig \
--log-dir /data/logs/kubernetes/kube-kubelet \
--pod-infra-container-image harbor.od.com/public/pause:latest \
--root-dir /data/kubelet
执行权限：
# chmod u+x /opt/kubernetes/server/bin/kubelet.sh
创建日志存储目录：
# mkdir -p /data/logs/kubernetes/kube-kubelet
编辑supervisord启动文件：红色部分自行修改
# vi /etc/supervisord.d/kube-kubelet.ini
[program:kube-kubelet-7-21]
command=/opt/kubernetes/server/bin/kubelet.sh ; the program (relative uses PATH, can take args)
numprocs=1 ; number of processes copies to start (def 1)
directory=/opt/kubernetes/server/bin ; directory to cwd to before exec (def no cwd)
autostart=true ; start at supervisord start (default: true)
autorestart=true ; retstart at unexpected quit (default: true)
startsecs=30 ; number of secs prog must stay running (def. 1)
startretries=3 ; max # of serial start failures (default 3)
exitcodes=0,2 ; 'expected' exit codes for process (default 0,2)
stopsignal=QUIT ; signal used to kill process (default TERM)
stopwaitsecs=10 ; max num secs to wait b4 SIGKILL (default 10)
user=root ; setuid to this UNIX account to run the program
redirect_stderr=true ; redirect proc stderr to stdout (default false)
stdout_logfile=/data/logs/kubernetes/kube-kubelet/kubelet.stdout.log ; stderr log path, NONE for none; default AUTO
stdout_logfile_maxbytes=64MB ; max # logfile bytes b4 rotation (default 50MB)
stdout_logfile_backups=4 ; # of stdout logfile backups (default 10)
stdout_capture_maxbytes=1MB ; number of bytes in'capturemode' (default 0)
stdout_events_enabled=false ; emit events on stdout writes (default false)
# supervisorctl update
# supervisorctl status
给node打tag：
# kubectl label node hdss7-21.host.com node-role.kubernetes.io/master=
