Kubernetes
Kubernetes是Google开源的容器集群管理系统。它构建Ddocker技术之上，为容器化的应用提供资源调度、部署运行、服务发现、扩容缩容等整一套功能，本质上可看作是基于容器技术的mini-PaaS平台。本文旨在梳理Kubernetes的架构、概念及基本工作流，并且通过运行一个简单的示例应用来介绍如何使用Kubernetes。
优点：
—轻量级、简单
—公有云、私有云、混合云部署
—模块化、可插拔化、可挂接、可组合
—自动恢复、自动重启、自动复制
内网系统中建议关闭防火墙服务：
# systemctl disable firewalld
# systemctl stop firewalld- 1
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修改/etc/hosts文件
# 192.168.123.201 kubernetes-master
# 192.168.123.202 kubernetes-node1
# 192.168.123.203 kubernetes-node2- 1
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关闭selinux
# vim /etc/selinux/config
SELINUX=disabled- 1
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关闭Docker的selinux功能
# vim /etc/sysconfig/docker
OPTIONS='--selinux-enabled=false'- 1
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1.Master上配置kube-apiserver,kube-controller-manager,kube-scheduler服务
(1) kube-apiserver服务
先确认etcd服务已经安装正确并启动，配置Kube-apiserver的启动参数
# yum install -y etcd
# vim /etc/etcd/etcd.conf
ETCD_LISTEN_CLIENT_URLS="http://0.0.0.0:2379"
# yum install -y kubernetes
# vim /usr/lib/systemd/system/kube-apiserver.service
[Unit]
Description=Kubernetes API Server
Documentation=https://github.com/GoogleCloudPlatform/kubernetes
Wants=etcd.service
After=etcd.service
[Service]
EnvironmentFile=-/etc/kubernetes/config
EnvironmentFile=-/etc/kubernetes/apiserver
User=kube
ExecStart=/usr/bin/kube-apiserver \
$KUBE_LOGTOSTDERR \
$KUBE_LOG_LEVEL \
$KUBE_ETCD_SERVERS \
$KUBE_API_ADDRESS \
$KUBE_API_PORT \
$KUBELET_PORT \
$KUBE_ALLOW_PRIV \
$KUBE_SERVICE_ADDRESSES \
$KUBE_ADMISSION_CONTROL \
$KUBE_API_ARGS
Restart=on-failure
Type=notify
LimitNOFILE=65536
[Install]
WantedBy=multi-user.target- 1
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配置文件/etc/kubernetes/config，文件的内容为所有服务都需要的参数
KUBE_LOGTOSTDERR="--logtostderr=true"
KUBE_LOG_LEVEL="--v=0"
KUBE_ALLOW_PRIV="--allow_privileged=false"
KUBE_MASTER="--master=http://kubernetes-master:8080"- 1
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配置文件/etc/kubernetes/apiserver，内容包括：绑定主机的IP地址、端口号、etcd服务地址、Service所需的Cluster IP池、一系列admission控制策略等
KUBE_API_ADDRESS="--address=0.0.0.0"
KUBE_API_PORT="--port=8080"
KUBE_ETCD_SERVERS="--etcd_servers=http://127.0.0.1:2379"
KUBE_SERVICE_ADDRESSES="--service-cluster-ip-range=10.254.0.0/16"
KUBE_ADMISSION_CONTROL="--admission_control=NamespaceLifecycle,NamespaceExists,LimitRanger,SecurityContextDeny,ServiceAccount,ResourceQuota"
KUBE_API_ARGS=""- 1
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(2) kube-controller-manager服务
kube-controller-manager服务依赖于etcd和kube-apiserver服务
# vim /usr/lib/systemd/system/kube-controller-manager.service
[Unit]
Description=Kubernetes Controller Manager
Documentation=https://github.com/GoogleCloudPlatform/kubernetes
After=etcd.service
After=kube-apiserver.service
Requires=etcd.service
Requires=kube-apiserver.service
[Service]
EnvironmentFile=-/etc/kubernetes/config
EnvironmentFile=-/etc/kubernetes/controller-manager
User=kube
ExecStart=/usr/bin/kube-controller-manager \
$KUBE_LOGTOSTDERR \
$KUBE_LOG_LEVEL \
$KUBE_MASTER \
$KUBE_CONTROLLER_MANAGER_ARGS
Restart=on-failure
LimitNOFILE=65536
[Install]
WantedBy=multi-user.target- 1
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(3) kube-scheduler服务
kube-scheduler服务也依赖于etcd和kube-apiserve
# vim /usr/lib/systemd/system/kube-scheduler.service
[Unit]
Description=Kubernetes Scheduler Plugin
Documentation=https://github.com/GoogleCloudPlatform/kubernetes
After=etcd.service
After=kube-apiserver.service
Requires=etcd.service
Requires=kube-apiserver.service
[Service]
EnvironmentFile=-/etc/kubernetes/config
EnvironmentFile=-/etc/kubernetes/scheduler
User=kube
ExecStart=/usr/bin/kube-scheduler \
$KUBE_LOGTOSTDERR \
$KUBE_LOG_LEVEL \
$KUBE_MASTER \
$KUBE_SCHEDULER_ARGS
Restart=on-failure
LimitNOFILE=65536
[Install]
WantedBy=multi-user.target- 1
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完成后，通过systemctl start命令启动3个服务。同时，使用systemctl enable命令将服务加入开机启动列表中。
# systemctl daemon-reload
# systemctl start etcd kube-apiserver.service kube-controller-manager kube-scheduler
# systemctl enable etcd kube-apiserver.service kube-controller-manager kube-scheduler- 1
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通过systemctl status 来验证服务启动的状态。
2.Node上配置kubelet,kube-proxy服务
(1) kubelet服务
配置kubelet服务，它依赖于Docker服务
# vim /usr/lib/systemd/system/kubelet.service
[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_ARGS
Restart=on-failure
[Install]
WantedBy=multi-user.target- 1
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修改配置文件/etc/kubernetes/kubelet，内容包括：绑定主机IP地址、端口号、apiserver的地址及其他参数
KUBELET_ADDRESS="--address=0.0.0.0"
KUBELET_PORT="--port=10250"
KUBELET_HOSTNAME="--hostname_override=kubernetes-node1"
KUBELET_API_SERVER="--api_servers=http://kubernetes-master:8080"
KUBELET_ARGS=""- 1
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(2) kube-proxy服务
配置kube-proxy服务，它依赖于Linux的network服务
# vim /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- 1
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配置文件/etc/kubernetes/proxy无须特别的参数设置
kubelet和kube-proxy都需要的配置文件/etc/kubernetes/config的内容示例如下：
KUBE_LOGTOSTDERR="--logtostderr=true"
KUBE_LOG_LEVEL="--v=0"
KUBE_ALLOW_PRIV="--allow_privileged=false"
KUBE_MASTER="--master=http://kubernetes-master:8080"- 1
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配置完成后，通过systemctl启动服务：
# systemctl daemon-reload
# systemctl start kubelet.service kube-proxy docker
# systemctl enable kubelet.service kube-proxy docker- 1
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kubelet默认采用向Master自注册的机制，在Master上查看名Node的状态(# kubelet get nodes)，状态为Ready表示Node向Master注册成功。
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