轻量级Kubernetes之k3s：5:集群搭建
在前面的文章中对k3s进行了一些概要信息和安装选项以及离线安装方式的介绍，这篇文章通过具体的实例来介绍如何使用k3s搭建kubernetes集群。
集群环境准备
| hostname | IP | 内存 | 硬盘 | 操作系统 | 用途 |
|---|---|---|---|---|---|
| host121 | 192.168.163.121 | 512MB | 8G | CentOS 7.6 | Master |
| host122 | 192.168.163.122 | 512MB | 5G | CentOS 7.6 | Node |
| host123 | 192.168.163.123 | 512MB | 5G | CentOS 7.6 | Node |
| host124 | 192.168.163.124 | 512MB | 5G | CentOS 7.6 | Node |
注：本来Node节点想用256MB，最小化安装安装失败了，普通方式下，搭建kubernetes集群所用的节点，512M也只能算是非常低的配置了。
步骤1: 安装部署Master节点
- 下载k3s二进制文件
执行命令：wget https://github.com/rancher/k3s/releases/download/v1.0.0/k3s
- 拷贝至/usr/local/bin下
执行命令：cp k3s /usr/local/bin/
- 设定执行权限
执行命令：chmod 755 /usr/local/bin/k3s
- 清空iptables规则
执行命令：iptables -F
- 确认版本
执行命令：k3s --version
执行日志如下所示：
[root@host121 ~]# wget https://github.com/rancher/k3s/releases/download/v1.0.0/k3s
...省略
[root@host121 ~]# cp k3s /usr/local/bin/
[root@host121 ~]# chmod 755 /usr/local/bin/k3s
[root@host121 ~]# iptables -F
[root@host121 ~]# k3s --version
k3s version v1.0.0 (18bd921c)
[root@host121 ~]#
- 下载安装脚本
执行命令：curl https://raw.githubusercontent.com/rancher/k3s/master/install.sh -o install.sh
- 设定离线安装方式进行安装
执行命令：export INSTALL_K3S_SKIP_DOWNLOAD=true && sh install.sh
- 确认kubernetes版本
执行命令：kubectl version
- 确认节点信息
执行命令：kubectl get node -o wide
执行日志如下所示：
[root@host121 ~]# curl https://raw.githubusercontent.com/rancher/k3s/master/install.sh -o install.sh
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 20421 100 20421 0 0 23031 0 --:--:-- --:--:-- --:--:-- 23022
[root@host121 ~]# export INSTALL_K3S_SKIP_DOWNLOAD=true && sh install.sh
[INFO] Skipping k3s download and verify
which: no kubectl in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin)
[INFO] Creating /usr/local/bin/kubectl symlink to k3s
which: no crictl in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin)
[INFO] Creating /usr/local/bin/crictl symlink to k3s
which: no ctr in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin)
[INFO] Creating /usr/local/bin/ctr symlink to k3s
[INFO] Creating killall script /usr/local/bin/k3s-killall.sh
[INFO] Creating uninstall script /usr/local/bin/k3s-uninstall.sh
[INFO] env: Creating environment file /etc/systemd/system/k3s.service.env
[INFO] systemd: Creating service file /etc/systemd/system/k3s.service
[INFO] systemd: Enabling k3s unit
Created symlink from /etc/systemd/system/multi-user.target.wants/k3s.service to /etc/systemd/system/k3s.service.
[INFO] systemd: Starting k3s
[root@host121 ~]# kubectl version
Client Version: version.Info{Major:"1", Minor:"16", GitVersion:"v1.16.3-k3s.2", GitCommit:"e7e6a3c4e9a7d80b87793612730d10a863a25980", GitTreeState:"clean", BuildDate:"2019-11-18T18:31:23Z", GoVersion:"go1.13.4", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"16", GitVersion:"v1.16.3-k3s.2", GitCommit:"e7e6a3c4e9a7d80b87793612730d10a863a25980", GitTreeState:"clean", BuildDate:"2019-11-18T18:31:23Z", GoVersion:"go1.13.4", Compiler:"gc", Platform:"linux/amd64"}
[root@host121 ~]# kubectl get node -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
host121 NotReady master 5s v1.16.3-k3s.2 192.168.163.121 CentOS Linux 7 (Core) 3.10.0-957.el7.x86_64 containerd://1.3.0-k3s.4
[root@host121 ~]#
cluster-info的详细信息
[root@host121 ~]# kubectl cluster-info
Kubernetes master is running at https://127.0.0.1:6443
CoreDNS is running at https://127.0.0.1:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
Metrics-server is running at https://127.0.0.1:6443/api/v1/namespaces/kube-system/services/https:metrics-server:/proxy
To further debug and diagnose cluster problems, use ‘kubectl cluster-info dump’.
[root@host121 ~]#
步骤2: 安装设定节点
- 事前准备
使用如下脚本进行事前准备，将k3s二进制文件拷贝至各节点的/usr/local/bin下，并设定执行权限
for host in host122 host123 host124
do
echo "# Copy k3s to $host"
scp k3s $host:/usr/local/bin/k3s
ssh $host "chmod 755 /usr/local/bin/k3s"
ssh $host "k3s --version"
echo
done
执行日志如下所示
[root@host121 ~]# for host in host122 host123 host124
> do
> echo "# Copy k3s to $host"
> scp k3s $host:/usr/local/bin/k3s
> ssh $host "chmod 755 /usr/local/bin/k3s"
> ssh $host "k3s --version"
> echo
> done
# Copy k3s to host122
k3s 100% 49MB 35.0MB/s 00:01
k3s version v1.0.0 (18bd921c)
# Copy k3s to host123
k3s 100% 49MB 34.6MB/s 00:01
k3s version v1.0.0 (18bd921c)
# Copy k3s to host124
k3s 100% 49MB 34.7MB/s 00:01
k3s version v1.0.0 (18bd921c)
[root@host121 ~]#
拷贝安装脚本至各节点，执行日志如下所示：
[root@host121 ~]# for host in host122 host123 host124; do echo "# Copy install.sh to $host"; scp install.sh ${host}:/root/install.sh; echo; done
# Copy install.sh to host122
install.sh 100% 20KB 995.1KB/s 00:00
# Copy install.sh to host123
install.sh 100% 20KB 7.5MB/s 00:00
# Copy install.sh to host124
install.sh 100% 20KB 7.2MB/s 00:00
[root@host121 ~]#
确认token信息
[root@host121 ~]# cat /var/lib/rancher/k3s/server/node-token
K10d7dd455049ee200cada3bf833b3157862a4d9ef07ab9785d3dc39f9b6a416fab::server:e55b636ebd8c962ae8721a8ab2ab0e4f
[root@host121 ~]#
安装非常简单，只需要正确设定K3S_URL和K3S_TOKEN然后执行安装脚本即可，以host122节点为例，执行日志如下所示：
[root@host122 ~]# export K3S_URL=https://192.168.163.121:6443
[root@host122 ~]# export K3S_TOKEN=K10d7dd455049ee200cada3bf833b3157862a4d9ef07ab9785d3dc39f9b6a416fab::server:e55b636ebd8c962ae8721a8ab2ab0e4f
[root@host122 ~]# export INSTALL_K3S_SKIP_DOWNLOAD=true && sh install.sh agent
[INFO] Skipping k3s download and verify
which: no kubectl in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin)
[INFO] Creating /usr/local/bin/kubectl symlink to k3s
which: no crictl in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin)
[INFO] Creating /usr/local/bin/crictl symlink to k3s
which: no ctr in (/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin)
[INFO] Creating /usr/local/bin/ctr symlink to k3s
[INFO] Creating killall script /usr/local/bin/k3s-killall.sh
[INFO] Creating uninstall script /usr/local/bin/k3s-agent-uninstall.sh
[INFO] env: Creating environment file /etc/systemd/system/k3s-agent.service.env
[INFO] systemd: Creating service file /etc/systemd/system/k3s-agent.service
[INFO] systemd: Enabling k3s-agent unit
Created symlink from /etc/systemd/system/multi-user.target.wants/k3s-agent.service to /etc/systemd/system/k3s-agent.service.
[INFO] systemd: Starting k3s-agent
[root@host122 ~]#
此时在master节点（host121）进行确认，可以得到如下信息
[root@host121 ~]# kubectl get node -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
host121 Ready master 6m9s v1.16.3-k3s.2 192.168.163.121 CentOS Linux 7 (Core) 3.10.0-957.el7.x86_64 containerd://1.3.0-k3s.4
host122 Ready 13s v1.16.3-k3s.2 192.168.163.122 CentOS Linux 7 (Core) 3.10.0-957.el7.x86_64 containerd://1.3.0-k3s.4
[root@host121 ~]#
同样的操作在host123和host124执行之后，再次确认可以得到几乎实时的构成节点信息的变化
[root@host121 ~]# kubectl get node -o wide
NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME
host121 Ready master 7m16s v1.16.3-k3s.2 192.168.163.121 CentOS Linux 7 (Core) 3.10.0-957.el7.x86_64 containerd://1.3.0-k3s.4
host122 Ready 80s v1.16.3-k3s.2 192.168.163.122 CentOS Linux 7 (Core) 3.10.0-957.el7.x86_64 containerd://1.3.0-k3s.4
host123 Ready 6s v1.16.3-k3s.2 192.168.163.123 CentOS Linux 7 (Core) 3.10.0-957.el7.x86_64 containerd://1.3.0-k3s.4
host124 Ready 3s v1.16.3-k3s.2 192.168.163.124 CentOS Linux 7 (Core) 3.10.0-957.el7.x86_64 containerd://1.3.0-k3s.4
[root@host121 ~]#
总结
从这篇文章可以看到，使用k3s无论是搭建单机版本还是搭建一个1主3从的集群都非常的简单，几分钟就可以完成，过程也几乎没有什么使用上的太多的大坑小坑，至少是学习k8s的必备神器。