使用Kubeadm(1.13+)快速搭建Kubernetes集群
Kubeadm是管理集群生命周期的重要工具,从创建到配置再到升级,Kubeadm处理现有硬件上的生产集群的引导,并以最佳实践方式配置核心Kubernetes组件,以便为新节点提供安全而简单的连接流程并支持轻松升级。随着Kubernetes 1.13 的发布,现在Kubeadm正式成为GA。
准备
首先准备2台虚拟机(CPU最少2核),我是使用Hyper-V创建的2台Ubuntu18.04虚拟机,IP和机器名如下:
172.17.20.210 master
172.17.20.211 node1
禁用Swap
Kubernetes 1.8开始要求必须禁用Swap,如果不关闭,默认配置下kubelet将无法启动。
编辑/etc/fstab
文件:
sudo vim /etc/fstab
UUID=8be04efd-f7c5-11e8-be8b-00155d000500 / ext4 defaults 0 0
UUID=C0E3-6A72 /boot/efi vfat defaults 0 0
#/swap.img none swap sw 0 0
如上,将/swap.img
所在的行注释掉,然后运行:
sudo swapoff -a
(可选)DNS配置
在Ubuntu18.04+版本中,DNS由systemd
全面接管,接口监听在127.0.0.53:53
,配置文件在/etc/systemd/resolved.conf
中。
有时候会导致无法解析域名的问题,可使用如下2种方式来解决:
1.最简单的就是关闭systemd-resolvd服务
sudo systemctl stop systemd-resolved
sudo systemctl disable systemd-resolved
然后手动修改/etc/resolv.conf
文件就可以了。
2.更加推荐的做法是修改systemd-resolv的设置:
sudo vim /etc/systemd/resolved.conf
# 修改为如下
[Resolve]
DNS=1.1.1.1 1.0.0.1
#FallbackDNS=
#Domains=
LLMNR=no
#MulticastDNS=no
#DNSSEC=no
#Cache=yes
#DNSStubListener=yes
DNS=设置的是域名解析服务器的IP地址,这里分别设为1.1.1.1和1.0.0.1
LLMNR=设置的是禁止运行LLMNR(Link-Local Multicast Name Resolution),否则systemd-resolve会监听5535端口。
安装Docker
Kubernetes从1.6开始使用CRI(Container Runtime Interface)容器运行时接口。默认的容器运行时仍然是Docker,是使用kubelet中内置dockershim CRI来实现的。
Docker的安装可以参考之前的博客:Docker初体验。
需要注意的是,Kubernetes 1.13已经针对Docker的1.11.1, 1.12.1, 1.13.1, 17.03, 17.06, 17.09, 18.06等版本做了验证,最低支持的Docker版本是1.11.1,最高支持是18.06,而Docker最新版本已经是
18.09
了,故我们安装时需要指定版本为18.06.1-ce
:sudo apt install docker-ce=18.06.1~ce~3-0~ubuntu
安装kubeadm, kubelet 和 kubectl
部署之前,我们需要安装三个包:
kubeadm: 引导启动k8s集群的命令行工具。
kubelet: 在群集中所有节点上运行的核心组件, 用来执行如启动pods和containers等操作。
kubectl: 操作集群的命令行工具。
首先添加apt-key:
sudo apt update && sudo apt install -y apt-transport-https curl
curl -s https://mirrors.aliyun.com/kubernetes/apt/doc/apt-key.gpg | sudo apt-key add -
添加kubernetes源:
sudo vim /etc/apt/sources.list.d/kubernetes.list
deb https://mirrors.aliyun.com/kubernetes/apt/ kubernetes-xenial main
安装:
sudo apt update
sudo apt install -y kubelet kubeadm kubectl
sudo apt-mark hold kubelet kubeadm kubectl
使用kubeadm创建一个单Master集群
初始化Master节点
K8s的控制面板组件运行在Master节点上,包括etcd和API server(Kubectl便是通过API server与k8s通信)。
在执行初始化之前,我们还有一下3点需要注意:
1.选择一个网络插件,并检查它是否需要在初始化Master时指定一些参数,比如我们可能需要根据选择的插件来设置--pod-network-cidr
参数。参考:Installing a pod network add-on。
2.kubeadm使用eth0的默认网络接口(通常是内网IP)做为Master节点的advertise address,如果我们想使用不同的网络接口,可以使用--apiserver-advertise-address=<ip-address>
参数来设置。如果适应IPv6,则必须使用IPv6d的地址,如:--apiserver-advertise-address=fd00::101
。
3.使用kubeadm config images pull
来预先拉取初始化需要用到的镜像,用来检查是否能连接到Kubenetes的Registries。
Kubenetes默认Registries地址是k8s.gcr.io
,很明显,在国内并不能访问gcr.io,因此在kubeadm v1.13之前的版本,安装起来非常麻烦,但是在1.13
版本中终于解决了国内的痛点,其增加了一个--image-repository
参数,默认值是k8s.gcr.io
,我们将其指定为国内镜像地址:registry.aliyuncs.com/google_containers
,其它的就可以完全按照官方文档来愉快的玩耍了。
其次,我们还需要指定--kubernetes-version
参数,因为它的默认值是stable-1
,会导致从https://dl.k8s.io/release/stable-1.txt
下载最新的版本号,我们可以将其指定为固定版本(最新版:v1.13.1)来跳过网络请求。
现在,我们就来试一下:
# 使用calico网络 --pod-network-cidr=192.168.0.0/16
sudo kubeadm init --image-repository registry.aliyuncs.com/google_containers --kubernetes-version v1.13.1 --pod-network-cidr=192.168.0.0/16
# 输出
[init] Using Kubernetes version: v1.13.1
[preflight] Running pre-flight checks
[preflight] Pulling images required for setting up a Kubernetes cluster
[preflight] This might take a minute or two, depending on the speed of your internet connection
[preflight] You can also perform this action in beforehand using 'kubeadm config images pull'
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Activating the kubelet service
[certs] Using certificateDir folder "/etc/kubernetes/pki"
[certs] Generating "ca" certificate and key
[certs] Generating "apiserver" certificate and key
[certs] apiserver serving cert is signed for DNS names [master kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 172.17.20.210]
[certs] Generating "apiserver-kubelet-client" certificate and key
[certs] Generating "front-proxy-ca" certificate and key
[certs] Generating "front-proxy-client" certificate and key
[certs] Generating "etcd/ca" certificate and key
[certs] Generating "etcd/peer" certificate and key
[certs] etcd/peer serving cert is signed for DNS names [master localhost] and IPs [172.17.20.210 127.0.0.1 ::1]
[certs] Generating "etcd/server" certificate and key
[certs] etcd/server serving cert is signed for DNS names [master localhost] and IPs [172.17.20.210 127.0.0.1 ::1]
[certs] Generating "etcd/healthcheck-client" certificate and key
[certs] Generating "apiserver-etcd-client" certificate and key
[certs] Generating "sa" key and public key
[kubeconfig] Using kubeconfig folder "/etc/kubernetes"
[kubeconfig] Writing "admin.conf" kubeconfig file
[kubeconfig] Writing "kubelet.conf" kubeconfig file
[kubeconfig] Writing "controller-manager.conf" kubeconfig file
[kubeconfig] Writing "scheduler.conf" kubeconfig file
[control-plane] Using manifest folder "/etc/kubernetes/manifests"
[control-plane] Creating static Pod manifest for "kube-apiserver"
[control-plane] Creating static Pod manifest for "kube-controller-manager"
[control-plane] Creating static Pod manifest for "kube-scheduler"
[etcd] Creating static Pod manifest for local etcd in "/etc/kubernetes/manifests"
[wait-control-plane] Waiting for the kubelet to boot up the control plane as static Pods from directory "/etc/kubernetes/manifests". This can take up to 4m0s
[kubelet-check] Initial timeout of 40s passed.
[apiclient] All control plane components are healthy after 42.003645 seconds
[uploadconfig] storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config-1.13" in namespace kube-system with the configuration for the kubelets in the cluster
[patchnode] Uploading the CRI Socket information "/var/run/dockershim.sock" to the Node API object "master" as an annotation
[mark-control-plane] Marking the node master as control-plane by adding the label "node-role.kubernetes.io/master=''"
[mark-control-plane] Marking the node master as control-plane by adding the taints [node-role.kubernetes.io/master:NoSchedule]
[bootstrap-token] Using token: 6pkrlg.8glf2fqpuf3i489m
[bootstrap-token] Configuring bootstrap tokens, cluster-info ConfigMap, RBAC Roles
[bootstraptoken] configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials
[bootstraptoken] configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token
[bootstraptoken] configured RBAC rules to allow certificate rotation for all node client certificates in the cluster
[bootstraptoken] creating the "cluster-info" ConfigMap in the "kube-public" namespace
[addons] Applied essential addon: CoreDNS
[addons] Applied essential addon: kube-proxy
Your Kubernetes master has initialized successfully!
To start using your cluster, you need to run the following as a regular user:
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
You should now deploy a pod network to the cluster.
Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:
https://kubernetes.io/docs/concepts/cluster-administration/addons/
You can now join any number of machines by running the following on each node
as root:
kubeadm join 172.17.20.210:6443 --token 6pkrlg.8glf2fqpuf3i489m --discovery-token-ca-cert-hash sha256:eebfe256113bee397b218ba832f412273ae734bd4686241fb910885d26efd222
这次非常顺利的就部署成功了,如果我们想使用非root用户操作kubectl
,可以使用以下命令,这也是kubeadm init
输出的一部分:
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
安装网络插件
为了让Pods间可以相互通信,我们必须安装一个网络插件,并且必须在部署任何应用之前安装,CoreDNS也是在网络插件安装之后才会启动的。
网络的插件完整列表,请参考 Networking and Network Policy。
在安装之前,我们先查看一下当前Pods的状态:
kubectl get pods --all-namespaces
# 输出
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system coredns-78d4cf999f-6pgfr 0/1 Pending 0 87s
kube-system coredns-78d4cf999f-m9kgs 0/1 Pending 0 87s
kube-system etcd-master 1/1 Running 0 47s
kube-system kube-apiserver-master 1/1 Running 0 38s
kube-system kube-controller-manager-master 1/1 Running 0 55s
kube-system kube-proxy-mkg24 1/1 Running 0 87s
kube-system kube-scheduler-master 1/1 Running 0 41s
如上,可以看到CoreDND的状态是Pending
,这是因为我们还没有安装网络插件。
Calico是一个纯三层的虚拟网络方案,Calico 为每个容器分配一个 IP,每个 host 都是 router,把不同 host 的容器连接起来。与 VxLAN 不同的是,Calico 不对数据包做额外封装,不需要 NAT 和端口映射,扩展性和性能都很好。
默认情况下,Calico网络插件使用的的网段是192.168.0.0/16
,在init
的时候,我们已经通过--pod-network-cidr=192.168.0.0/16
来适配Calico,当然你也可以修改calico.yml
文件来指定不同的网段。
可以使用如下命令命令来安装Canal
插件:
kubectl apply -f https://docs.projectcalico.org/v3.3/getting-started/kubernetes/installation/hosted/rbac-kdd.yaml
kubectl apply -f https://docs.projectcalico.org/v3.3/getting-started/kubernetes/installation/hosted/kubernetes-datastore/calico-networking/1.7/calico.yaml
# 上面的calico.yaml会去quay.io拉取镜像,如果无法拉取,可使用下面的国内镜像
kubectl apply -f http://mirror.faasx.com/k8s/calico/v3.3.2/rbac-kdd.yaml
kubectl apply -f http://mirror.faasx.com/k8s/calico/v3.3.2/calico.yaml
关于更多Canal
的信息可以查看Calico官方文档:kubeadm quickstart。
稍等片刻,再使用kubectl get pods --all-namespaces
命令来查看网络插件的安装情况:
kubectl get pods --all-namespaces
# 输出
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system calico-node-x96gn 2/2 Running 0 47s
kube-system coredns-78d4cf999f-6pgfr 1/1 Running 0 54m
kube-system coredns-78d4cf999f-m9kgs 1/1 Running 0 54m
kube-system etcd-master 1/1 Running 3 53m
kube-system kube-apiserver-master 1/1 Running 3 53m
kube-system kube-controller-manager-master 1/1 Running 3 53m
kube-system kube-proxy-mkg24 1/1 Running 2 54m
kube-system kube-scheduler-master 1/1 Running 3 53m
如上,STATUS全部变为了Running
,表示安装成功,接下来就可以加入其他节点以及部署应用了。
Master隔离
默认情况下,由于安全原因,集群并不会将pods部署在Master节点上。但是在开发环境下,我们可能就只有一个Master节点,这时可以使用下面的命令来解除这个限制:
kubectl taint nodes --all node-role.kubernetes.io/master-
## 输出
node/master untainted
加入工作节点
要为群集添加工作节点,需要为每台计算机执行以下操作:
- SSH到机器
- 成为root用户,(如: sudo su -)
- 运行上面的
kubeadm init
命令输出的:kubeadm join --token <token> <master-ip>:<master-port> --discovery-token-ca-cert-hash sha256:<hash>
如果我们忘记了Master节点的加入token,可以使用如下命令来查看:
kubeadm token list
# 输出
TOKEN TTL EXPIRES USAGES DESCRIPTION EXTRA GROUPS
6pkrlg.8glf2fqpuf3i489m 22h 2018-12-07T13:46:33Z authentication,signing The default bootstrap token generated by 'kubeadm init'. system:bootstrappers:kubeadm:default-node-token
默认情况下,token的有效期是24小时,如果我们的token已经过期的话,可以使用以下命令重新生成:
kubeadm token create
# 输出
u2mt59.tyqpo0v5wf05lx2q
如果我们也没有--discovery-token-ca-cert-hash
的值,可以使用以下命令生成:
openssl x509 -pubkey -in /etc/kubernetes/pki/ca.crt | openssl rsa -pubin -outform der 2>/dev/null | openssl dgst -sha256 -hex | sed 's/^.* //'
# 输出
eebfe256113bee397b218ba832f412273ae734bd4686241fb910885d26efd222
现在,我们登录到工作节点服务器,然后运行如下命令加入集群(这也是上面init
输出的一部分):
sudo kubeadm join 172.17.20.210:6443 --token 6pkrlg.8glf2fqpuf3i489m --discovery-token-ca-cert-hash sha256:eebfe256113bee397b218ba832f412273ae734bd4686241fb910885d26efd222
# 输出
[sudo] password for raining:
[preflight] Running pre-flight checks
[discovery] Trying to connect to API Server "172.17.20.210:6443"
[discovery] Created cluster-info discovery client, requesting info from "https://172.17.20.210:6443"
[discovery] Requesting info from "https://172.17.20.210:6443" again to validate TLS against the pinned public key
[discovery] Cluster info signature and contents are valid and TLS certificate validates against pinned roots, will use API Server "172.17.20.210:6443"
[discovery] Successfully established connection with API Server "172.17.20.210:6443"
[join] Reading configuration from the cluster...
[join] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
[kubelet] Downloading configuration for the kubelet from the "kubelet-config-1.13" ConfigMap in the kube-system namespace
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[kubelet-start] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"
[kubelet-start] Activating the kubelet service
[tlsbootstrap] Waiting for the kubelet to perform the TLS Bootstrap...
[patchnode] Uploading the CRI Socket information "/var/run/dockershim.sock" to the Node API object "node1" as an annotation
This node has joined the cluster:
* Certificate signing request was sent to apiserver and a response was received.
* The Kubelet was informed of the new secure connection details.
Run 'kubectl get nodes' on the master to see this node join the cluster.
等待一会,我们可以在Master节点上使用kubectl get nodes
命令来查看节点的状态:
kubectl get nodes
# 输出
NAME STATUS ROLES AGE VERSION
master Ready master 17m v1.13.1
node1 Ready <none> 15m v1.13.1
如上全部Ready
,大功告成,我们可以运行一些命令来测试一下集群是否正常。
测试
首先验证kube-apiserver, kube-controller-manager, kube-scheduler, pod network 是否正常:
# 部署一个 Nginx Deployment,包含两个Pod
# https://kubernetes.io/docs/concepts/workloads/controllers/deployment/
kubectl create deployment nginx --image=nginx:alpine
kubectl scale deployment nginx --replicas=2
# 验证Nginx Pod是否正确运行,并且会分配192.168.开头的集群IP
kubectl get pods -l app=nginx -o wide
# 输出如下:
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx-54458cd494-p8jzs 1/1 Running 0 31s 192.168.1.2 node1 <none> <none>
nginx-54458cd494-v2m4b 1/1 Running 0 24s 192.168.1.3 node1 <none> <none>
再验证一下kube-proxy
是否正常:
# 以 NodePort 方式对外提供服务 https://kubernetes.io/docs/concepts/services-networking/connect-applications-service/
kubectl expose deployment nginx --port=80 --type=NodePort
# 查看集群外可访问的Port
kubectl get services nginx
# 输出
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
nginx NodePort 10.110.49.49 <none> 80:31899/TCP 4s
# 可以通过任意 NodeIP:Port 在集群外部访问这个服务,本示例中部署的2台集群IP分别是172.17.20.210和172.17.20.211
curl http://172.17.20.210:31899
curl http://172.17.20.211:31899
最后验证一下dns, pod network是否正常:
# 运行Busybox并进入交互模式
kubectl run -it curl --image=radial/busyboxplus:curl
# 输入`nslookup nginx`查看是否可以正确解析出集群内的IP,已验证DNS是否正常
[ root@curl-66959f6557-6sfqh:/ ]$ nslookup nginx
# 输出
Server: 10.96.0.10
Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local
Name: nginx
Address 1: 10.110.49.49 nginx.default.svc.cluster.local
# 通过服务名进行访问,验证kube-proxy是否正常
[ root@curl-66959f6557-6sfqh:/ ]$ curl http://nginx/
# 输出如下:
# <!DOCTYPE html> ---省略
# 分别访问一下2个Pod的内网IP,验证跨Node的网络通信是否正常
[ root@curl-66959f6557-6sfqh:/ ]$ curl http://192.168.1.2/
[ root@curl-66959f6557-6sfqh:/ ]$ curl http://192.168.1.3/
验证通过,集群搭建成功,接下来我们就可以参考官方文档来部署其他服务,愉快的玩耍了。
卸载集群
想要撤销kubeadm执行的操作,首先要排除节点,并确保该节点为空, 然后再将其关闭。
在Master节点上运行:
kubectl drain <node name> --delete-local-data --force --ignore-daemonsets
kubectl delete node <node name>
然后在需要移除的节点上,重置kubeadm的安装状态:
sudo kubeadm reset
如果你想重新配置集群,使用新的参数重新运行kubeadm init
或者kubeadm join
即可。
参考资料
Memo
本文转载至 https://www.cnblogs.com/RainingNight/p/using-kubeadm-to-create-a-cluster-1-13.html