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Cluster Overview

Contents

Information:

Container Layer

Scenario: Use Containerd service to manage our images and containers via command nerdctl, which is same concept with Docker.

  • Get namespace.
  • Get containers.
  • Get images.
  • Get volumes.
  • Get overall status.
  • Get network status.

Demo:

Get namespaces.

sudo nerdctl namespace ls

Result

NAME      CONTAINERS    IMAGES    VOLUMES    LABELS
k8s.io    21            30        0

Get containers under specific namespace k8s.io.

sudo nerdctl -n k8s.io ps

Result

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

Get images.

sudo nerdctl -n k8s.io image ls -a

Get volumes. After inintial installation, no volume within namespaces.

sudo nerdctl -n k8s.io volume ls

Get overall status

sudo nerdctl stats

Get network status.

sudo nerdctl network ls
sudo nerdctl network inspect bridge
sudo nerdctl network inspect k8s-pod-network

Result

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.

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  :

Kubernetes Layer

Scenario:

  • Nodes
  • Namespaces
  • System Pods

Demo:

Information:

  • In the demo, there are three nodes, cka001, cka002, and cka003.

Get nodes status.

kubectl get node -o wide

There are four initial namespaces across three nodes.

kubectl get namespace -A

Result

NAME              STATUS   AGE
default           Active   56m
kube-node-lease   Active   56m
kube-public       Active   56m
kube-system       Active   56m

There are some initial pods.

kubectl get pod -A -o wide

Result

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>

Summary:

Below shows the relationship between containers and pods.

  • 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

Reference