CKA自学笔记6:Kubernetes集群概览 ¶
摘要 ¶
包含下面内容：
- 容器层
- Kubernetes层
提示：
后续实验环境都是使用在阿里云部署的Ubuntu三节点集群，三个节点分别为 cka001、cka002 和 cka003。
容器层 ¶
场景：
使用Containerd服务，通过命令nerdctl来管理我们的镜像和容器，这与Docker的概念相同。
- Get namespace.
- Get containers.
- Get images.
- Get volumes.
- Get overall status.
- Get network status.
演示：
读取命名空间namespaces。
sudo nerdctl namespace ls
运行结果：
NAME CONTAINERS IMAGES VOLUMES LABELS
k8s.io 21 30 0
读取命名空间 k8s.io下的容器。
sudo nerdctl -n k8s.io ps
运行结果：
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
0a3625f22f65 registry.aliyuncs.com/google_containers/pause:3.6 "/pause" 16 hours ago Up k8s://kube-system/coredns-74586cf9b6-4jwmk
121af2ecd1a1 registry.aliyuncs.com/google_containers/coredns:v1.8.6 "/coredns -conf /etc…" 16 hours ago Up k8s://kube-system/coredns-74586cf9b6-c5mll/coredns
49f6c7e3efe5 registry.aliyuncs.com/google_containers/kube-proxy:v1.24.0 "/usr/local/bin/kube…" 16 hours ago Up k8s://kube-system/kube-proxy-dmj2t/kube-proxy
4bba5fbd701d registry.aliyuncs.com/google_containers/pause:3.6 "/pause" 16 hours ago Up k8s://kube-system/kube-scheduler-cka001
57d47b57eb12 docker.io/calico/node:v3.23.3 "start_runit" 16 hours ago Up k8s://kube-system/calico-node-w8nvl/calico-node
5ce4c351a886 registry.aliyuncs.com/google_containers/pause:3.6 "/pause" 16 hours ago Up k8s://kube-system/calico-node-w8nvl
6456eef784bf registry.aliyuncs.com/google_containers/kube-scheduler:v1.24.0 "kube-scheduler --au…" 16 hours ago Up k8s://kube-system/kube-scheduler-cka001/kube-scheduler
6a687305871c registry.aliyuncs.com/google_containers/kube-apiserver:v1.24.0 "kube-apiserver --ad…" 16 hours ago Up k8s://kube-system/kube-apiserver-cka001/kube-apiserver
7dcb24568574 registry.aliyuncs.com/google_containers/pause:3.6 "/pause" 16 hours ago Up k8s://kube-system/coredns-74586cf9b6-c5mll
a06b101118b8 registry.aliyuncs.com/google_containers/pause:3.6 "/pause" 16 hours ago Up k8s://kube-system/kube-controller-manager-cka001
a07ef8c3fc3a registry.aliyuncs.com/google_containers/pause:3.6 "/pause" 16 hours ago Up k8s://kube-system/etcd-cka001
b8566d3e4174 registry.aliyuncs.com/google_containers/kube-controller-manager:v1.24.0 "kube-controller-man…" 16 hours ago Up k8s://kube-system/kube-controller-manager-cka001/kube-controller-manager
ca6ac26314ff registry.aliyuncs.com/google_containers/coredns:v1.8.6 "/coredns -conf /etc…" 16 hours ago Up k8s://kube-system/coredns-74586cf9b6-4jwmk/coredns
cdc041b4791e registry.aliyuncs.com/google_containers/etcd:3.5.3-0 "etcd --advertise-cl…" 16 hours ago Up k8s://kube-system/etcd-cka001/etcd
e0c59abadf2e registry.aliyuncs.com/google_containers/pause:3.6 "/pause" 16 hours ago Up k8s://kube-system/kube-proxy-dmj2t
e0d2e5f6ccff registry.aliyuncs.com/google_containers/pause:3.6 "/pause" 16 hours ago Up k8s://kube-system/kube-apiserver-cka001
读取命名空间 k8s.io下的镜像。
sudo nerdctl -n k8s.io image ls -a
读取命名空间 k8s.io下的卷Volume。初始化安装后，该命名空间下没有任何卷。
sudo nerdctl -n k8s.io volume ls
读取集群状态。
sudo nerdctl stats
读取网络状态。
sudo nerdctl network ls
sudo nerdctl network inspect bridge
sudo nerdctl network inspect k8s-pod-network
运行结果：
NETWORK ID NAME FILE
k8s-pod-network /etc/cni/net.d/10-calico.conflist
0 bridge /etc/cni/net.d/nerdctl-bridge.conflist
host
none
Get network interface in host cka001 with command ip addr list.
IP pool of 10.4.0.1/24 is ipam and defined in /etc/cni/net.d/nerdctl-bridge.conflist.
使用命令ip addr list获取主机cka001的网络接口。10.4.0.1/24的IP池是ipam，在/etc/cni/net.d/nerdctl-bridge.conflist中定义。
lo : inet 127.0.0.1/8 qlen 1000
eth0 : inet <cka001_ip>/24 brd xxx.xxx.xxx.255 scope global dynamic eth0
tunl0@NONE : inet 10.244.228.192/32 scope global tunl0
cali96e32d88db2@if4 :
cali93613212490@if4 :
nerdctl-bridge.conflist文件的作用是：
- 定义了nerdctl使用的默认桥接CNI网络的配置，包括网络名称、子网、网关、IP分配策略等1 ，2。
- 使得nerdctl可以使用docker run -it --rm alpine这样的命令来运行一个容器，并自动分配一个10.4.0.0/24网段的IP地址1，3。
- 使得nerdctl可以支持一些基本的CNI插件，如bridge, portmap, firewall, tuning1，2。
Kubernetes层 ¶
场景：
- 节点Nodes
- 命名空间Namespaces
- 系统Pods
演示：
读取节点状态：
kubectl get node -o wide
在三个节点上有四个初始的命名空间。
kubectl get namespace -A
运行结果：
NAME STATUS AGE
default Active 56m
kube-node-lease Active 56m
kube-public Active 56m
kube-system Active 56m
在三个节点上的初始化Pod。
kubectl get pod -A -o wide
运行结果：
NAMESPACE NAME READY STATUS RESTARTS AGE NODE NOMINATED NODE READINESS GATES
kube-system calico-kube-controllers-555bc4b957-l8bn2 1/1 Running 0 15h cka003 <none> <none>
kube-system calico-node-255pc 1/1 Running 0 15h cka003 <none> <none>
kube-system calico-node-7tmnb 1/1 Running 0 15h cka002 <none> <none>
kube-system calico-node-w8nvl 1/1 Running 0 15h cka001 <none> <none>
kube-system coredns-74586cf9b6-4jwmk 1/1 Running 0 15h cka001 <none> <none>
kube-system coredns-74586cf9b6-c5mll 1/1 Running 0 15h cka001 <none> <none>
kube-system etcd-cka001 1/1 Running 0 15h cka001 <none> <none>
kube-system kube-apiserver-cka001 1/1 Running 0 15h cka001 <none> <none>
kube-system kube-controller-manager-cka001 1/1 Running 0 15h cka001 <none> <none>
kube-system kube-proxy-dmj2t 1/1 Running 0 15h cka001 <none> <none>
kube-system kube-proxy-n77zw 1/1 Running 0 15h cka002 <none> <none>
kube-system kube-proxy-qs6rf 1/1 Running 0 15h cka003 <none> <none>
kube-system kube-scheduler-cka001 1/1 Running 0 15h cka001 <none> <none>
总结： 下面列出了初始集群中主节点和所有节点中所包含的容器和Pod的关系。
- Master node:
- CoreDNS: 2 Pod
- etcd: 1 Pod
- apiserver: 1 Pod
- controller-manager: 1 Pod
- scheduler: 1 Pod
- Calico Controller: 1 Pod
- All nodes:
- Calico Node: 1 Pod each
- Proxy: 1 Pod each
参考：