K8s overview and cluster environment construction

I learned docker before and wanted to learn K8S in a complete set.

Reference: https://www.kubernetes.org.cn/k8s

1. Overview of kubernetes

1. Basic introduction

kubernetes is short for k8s, because there are eight words' ubernet 'between K and s, so it is short for k8s. K8s is an open source application for managing containerized applications on multiple hosts in the cloud platform. The goal of k8s is to make the deployment of containerized applications simple and efficient. K8s provides a mechanism for application deployment, planning, updating and maintenance. It is an open source container orchestration engine of google. It supports automatic deployment, large-scale scalability and application container management.

The latest deployment method is realized by deploying containers. Each container is isolated from each other. Each container has its own file system. Processes between containers will not affect each other and can distinguish computing resources. Compared with virtual machines, containers can be deployed quickly. Because containers are decoupled from underlying facilities and machine file systems, they can be migrated between different clouds and different versions of operating systems.

When an application is deployed in a production environment, multiple instances of the application are usually deployed to load balance the application requests. In k8s, we can create multiple containers, run one instance in each container, and then manage, discover and access this group of application instances through the built-in load balancing strategy.

2. k8s function

1. Automatic packing: automatically deploy application containers based on the resource configuration requirements of the container for the application running environment

2. Self repair: when the container fails, the container will be restarted; When there is a problem with the deployed node, the container will be redeployed and rescheduled

3. Horizontal expansion: realize service discovery and load balancing based on kubernetes' own capabilities

4. Rolling update: update the applications running in the application container at one time or in batch according to the changes of applications

5. Version fallback

6. Secret key and configuration management: the secret key and application configuration can be deployed and updated without rebuilding the image, similar to hot deployment

7. Storage arrangement: automatically realize storage system mounting and application, especially for stateful applications to realize data persistence. The storage system can come from local directory, network storage, public cloud storage and other services

8. Batch processing: provides one-time tasks and scheduled tasks to meet the scenario of batch data sorting and analysis

3. k8s cluster architecture and core concepts

1. Cluster architecture

(1) master} master node: performs scheduling management on the cluster and receives operation requests from users outside the cluster

apiserver: the only entry for resource operation, and provides mechanisms such as authentication, authorization, access control, API registration and discovery. It is delivered to etcd for storage in a restful manner

scheduler: node scheduling, select node node application deployment; The Pod is scheduled to the corresponding machine according to the predetermined scheduling policy

controller manager: it is responsible for maintaining the status of the cluster, such as fault detection, automatic expansion, rolling update, etc. one resource corresponds to one controller

etcd: storage system, which is used to save cluster related data, such as status data, pod data, etc

(2) The worker node is a work node that runs the user's business application container

kubelet: in short, it is the representative sent by the master to the node node to manage the related operations of the local container. Responsible for maintaining the life cycle of containers, as well as Volume (CVI) and network (CNI) management

Kube proxy: proxy on the network, including load balancing and other operations. Responsible for providing Service discovery and load balancing within the cluster for services

2. Core concepts

(1) pod: the smallest unit of k8s deployment. A pod can contain multiple containers, that is, a set of containers; Container internal sharing network; The life cycle of a pod is short, and a new pod is deployed.

pod is the basis of all business types in K8s cluster. It can be regarded as a small robot running in K8s cluster. Different types of businesses need different types of small robots to execute. At present, the services in K8s can be divided into long-running, batch, node daemon and stateful application; The corresponding small robot controllers are Deployment, Job, daemon set and PetSet

(2) Replication controller:

RC is the earliest API object in K8s cluster to ensure high availability of Pod. Monitor the running Pod to ensure that the specified number of Pod copies are running in the cluster. The specified number can be multiple or 1; If it is less than the specified number, RC will start running a new Pod copy; More than the specified number, RC will kill the excess Pod

Copy. Even when the specified number is 1, running Pod through RC is more wise than running Pod directly, because RC can also give full play to its highly available ability to ensure that one Pod is running forever. RC is an early technical concept of K8s, which is only applicable to long-term servo business types, such as controlling small robots to provide high availability

Web services.

(3)Service: defines access rules for a group of pod s. Each service corresponds to a valid virtual IP in the cluster, and a service is accessed through the virtual IP in the cluster.

Define rules for unified access through the service, and create a pod through the controller for deployment.

3. Cluster construction method

Currently, there are two deployment k8s methods:

(1) kubeadm

Kubedm is a k8s deployment tool that provides kubedm init and kube join for rapid deployment of k8s clusters. Official website: https://kubernetes.io/docs/reference/setup-tools/kubeadm/

(2) Binary package

Download the binary package of the distribution from github and manually deploy each component to form a k8s cluster.

kubeadm deployment is relatively simple, but it shields many details, and it may be difficult to troubleshoot problems. Binary package deployment k8s cluster can learn many principles and is also conducive to later maintenance.

2. k8s cluster construction

Simply build a master and two node s. The related machines and ip configurations are as follows: each machine needs to access the Internet to download related dependencies


1. System initialization (unless master is specified, all three nodes execute)

All three machines need to do the following operations. I choose to use a virtual machine and then clone it

1. Turn off the firewall

systemctl stop firewalld
systemctl disable firewalld
systemctl status firewalld View firewall status

2. Close selinux

sed -i 's/enforcing/disabled/' /etc/selinux/config  # permanent
setenforce 0  # temporary

3. Close swap

free -g #View partition status
swapoff -a #Temporarily Closed
sed -ri 's/.*swap.*/#&/' /etc/fstab #Permanent shutdown

4. Modify host name

hostnamectl set-hostname <hostname>

5. Change the IP address to static IP (note that DNS needs to be set to set static IP, refer to the previous rocketmq cluster)

vim /etc/sysconfig/network-scripts/ifcfg-ens33

6. Synchronization time

yum install ntpdate -y
ntpdate time.windows.com

7. In the master node, modify hosts and configure the reachability of hosts

cat >> /etc/hosts << EOF k8smaster1 k8snode1 k8snode2

8. Transfer the bridged IPv4 traffic to the iptables chain

cat > /etc/sysctl.d/k8s.conf << EOF
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
--system # take effect

9. Install docker / kubedm / kubelet on all nodes

By default, the CRI (container runtime) of Kubernetes is Docker, so Docker is installed first.

(1) Install Docker

wget https://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo -O /etc/yum.repos.d/docker-ce.repo
yum -y install docker-ce-18.06.1.ce-3.el7
systemctl enable docker && systemctl start docker
docker --version

(2) Add alicloud YUM software source

Set warehouse address

cat > /etc/docker/daemon.json << EOF
"registry-mirrors": ["https://b9pmyelo.mirror.aliyuncs.com"]

Add yum source:

cat > /etc/yum.repos.d/kubernetes.repo << EOF
gpgkey=https://mirrors.aliyun.com/kubernetes/yum/doc/yum-key.gpg https://mirrors.aliyun.com/kubernetes/yum/doc/rpm-package-key.gpg

(3) Install kubedm, kubelet, and kubectl

yum install -y kubelet-1.18.0 kubeadm-1.18.0 kubectl-1.18.0
systemctl enable kubelet

After successful installation, relevant information can be verified:

[root@k8smaster1 ~]# kubeadm version
kubeadm version: &version.Info{Major:"1", Minor:"18", GitVersion:"v1.18.0", GitCommit:"9e991415386e4cf155a24b1da15becaa390438d8", GitTreeState:"clean", BuildDate:"2020-03-25T14:56:30Z", GoVersion:"go1.13.8", Compiler:"gc", Platform:"linux/amd64"}
[root@k8smaster1 ~]# kubelet --version
Kubernetes v1.18.0

2. Deploy k8s master

 1. On the master node:

kubeadm init --apiserver-advertise-address= --image-repository registry.aliyuncs.com/google_containers --kubernetes-version v1.18.0 --service-cidr= --pod-network-cidr=

The apiserver advertisement address needs to be modified to the IP address of the master node; Specify the address of Alibaba cloud image warehouse at the destination; The third is to specify the kubernetes version; The latter two specify the IP addresses for internal access, as long as they do not conflict with the current network segment. If an error is reported above, you can add -- v=6 to view the detailed log. For a detailed explanation of kubedm parameters, please refer to the official website.  

After executing the above command, a series of docker images will be pulled. You can open a new terminal, and then use docker images to view the relevant images and containers as follows:

[root@k8smaster1 ~]# docker images
REPOSITORY                                                        TAG                 IMAGE ID            CREATED             SIZE
registry.aliyuncs.com/google_containers/kube-proxy                v1.18.0             43940c34f24f        21 months ago       117MB
registry.aliyuncs.com/google_containers/kube-scheduler            v1.18.0             a31f78c7c8ce        21 months ago       95.3MB
registry.aliyuncs.com/google_containers/kube-apiserver            v1.18.0             74060cea7f70        21 months ago       173MB
registry.aliyuncs.com/google_containers/kube-controller-manager   v1.18.0             d3e55153f52f        21 months ago       162MB
registry.aliyuncs.com/google_containers/pause                     3.2                 80d28bedfe5d        23 months ago       683kB
registry.aliyuncs.com/google_containers/coredns                   1.6.7               67da37a9a360        23 months ago       43.8MB
registry.aliyuncs.com/google_containers/etcd                      3.4.3-0             303ce5db0e90        2 years ago         288MB
[root@k8smaster1 ~]# docker ps
CONTAINER ID        IMAGE                                               COMMAND                  CREATED             STATUS              PORTS               NAMES
3877168ddb09        43940c34f24f                                        "/usr/local/bin/kube..."   3 minutes ago       Up 3 minutes                            k8s_kube-proxy_kube-proxy-hn4gx_kube-system_fe8347ac-3c81-4cab-ba78-3da6ad598316_0
18a32d328d49        registry.aliyuncs.com/google_containers/pause:3.2   "/pause"                 3 minutes ago       Up 3 minutes                            k8s_POD_kube-proxy-hn4gx_kube-system_fe8347ac-3c81-4cab-ba78-3da6ad598316_0
5f62d3184cd7        303ce5db0e90                                        "etcd --advertise-cl..."   3 minutes ago       Up 3 minutes                            k8s_etcd_etcd-k8smaster1_kube-system_635d8dc817fc23c8a6c09070c81f668f_0
2af2a1b5d169        a31f78c7c8ce                                        "kube-scheduler --au..."   3 minutes ago       Up 3 minutes                            k8s_kube-scheduler_kube-scheduler-k8smaster1_kube-system_ca2aa1b3224c37fa1791ef6c7d883bbe_0
c77506ee4dd2        d3e55153f52f                                        "kube-controller-man..."   3 minutes ago       Up 3 minutes                            k8s_kube-controller-manager_kube-controller-manager-k8smaster1_kube-system_c4d2dd4abfffdee4d424ce839b0de402_0
303545e4eca9        74060cea7f70                                        "kube-apiserver --ad..."   3 minutes ago       Up 3 minutes                            k8s_kube-apiserver_kube-apiserver-k8smaster1_kube-system_ba7276261300df6a615a2d947d86d3fa_0
f9da54e2bfae        registry.aliyuncs.com/google_containers/pause:3.2   "/pause"                 3 minutes ago       Up 3 minutes                            k8s_POD_kube-scheduler-k8smaster1_kube-system_ca2aa1b3224c37fa1791ef6c7d883bbe_0
007e2a0cd10b        registry.aliyuncs.com/google_containers/pause:3.2   "/pause"                 3 minutes ago       Up 3 minutes                            k8s_POD_kube-controller-manager-k8smaster1_kube-system_c4d2dd4abfffdee4d424ce839b0de402_0
0666c8b43c32        registry.aliyuncs.com/google_containers/pause:3.2   "/pause"                 3 minutes ago       Up 3 minutes                            k8s_POD_kube-apiserver-k8smaster1_kube-system_ba7276261300df6a615a2d947d86d3fa_0
0ca472d7f2cd        registry.aliyuncs.com/google_containers/pause:3.2   "/pause"                 3 minutes ago       Up 3 minutes                            k8s_POD_etcd-k8smaster1_kube-system_635d8dc817fc23c8a6c09070c81f668f_0

Finally, after the download is completed, the main window prompts as follows: (it can be regarded as successful when you see successful)

[kubelet-finalize] Updating "/etc/kubernetes/kubelet.conf" to point to a rotatable kubelet client certificate and key
[addons] Applied essential addon: CoreDNS
[addons] Applied essential addon: kube-proxy

Your Kubernetes control-plane 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:

Then you can join any number of worker nodes by running the following on each as root:

kubeadm join --token tcpixp.g14hyo8skehh9kcp \
    --discovery-token-ca-cert-hash sha256:6129c85d48cbf0ca946ea2c65fdc1055c12363be07b18dd7994c3c0a242a286a 

Use kubectl tool: execute the above information after success

  mkdir -p $HOME/.kube
  sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
  sudo chown $(id -u):$(id -g) $HOME/.kube/config


[root@k8smaster1 ~]# kubectl get nodes
k8smaster1   NotReady   master   7m17s   v1.18.0
[root@k8smaster1 ~]# kubectl version
Client Version: version.Info{Major:"1", Minor:"18", GitVersion:"v1.18.0", GitCommit:"9e991415386e4cf155a24b1da15becaa390438d8", GitTreeState:"clean", BuildDate:"2020-03-25T14:58:59Z", GoVersion:"go1.13.8", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"18", GitVersion:"v1.18.0", GitCommit:"9e991415386e4cf155a24b1da15becaa390438d8", GitTreeState:"clean", BuildDate:"2020-03-25T14:50:46Z", GoVersion:"go1.13.8", Compiler:"gc", Platform:"linux/amd64"}

 3. Join Kubernetes Node

Execute the following commands on the k8snode1 and k8snode2 nodes. Add a new node to the cluster and execute the kubedm join command output in kubedm init (with token related):

kubeadm join --token tcpixp.g14hyo8skehh9kcp \
    --discovery-token-ca-cert-hash sha256:6129c85d48cbf0ca946ea2c65fdc1055c12363be07b18dd7994c3c0a242a286a

It should be noted that only the kubedm join related parameters printed on the master console can be used here. Because tokens are different, the default token is valid for 24 hours. When it expires, the token will not be available. At this time, you need to recreate the token. You can refer to the official website and use the kubedm token related commands.

After the join succeeds, the output log is as follows:

[root@k8snode1 ~]# kubeadm join --token tcpixp.g14hyo8skehh9kcp \
>     --discovery-token-ca-cert-hash sha256:6129c85d48cbf0ca946ea2c65fdc1055c12363be07b18dd7994c3c0a242a286a
W0108 21:20:24.380628   25524 join.go:346] [preflight] WARNING: JoinControlPane.controlPlane settings will be ignored when control-plane flag is not set.
[preflight] Running pre-flight checks
        [WARNING IsDockerSystemdCheck]: detected "cgroupfs" as the Docker cgroup driver. The recommended driver is "systemd". Please follow the guide at https://kubernetes.io/docs/setup/cri/
        [WARNING Hostname]: hostname "k8snode1" could not be reached
        [WARNING Hostname]: hostname "k8snode1": lookup k8snode1 on no such host
[preflight] Reading configuration from the cluster...
[preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml'
[kubelet-start] Downloading configuration for the kubelet from the "kubelet-config-1.18" 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] Starting the kubelet
[kubelet-start] Waiting for the kubelet to perform the TLS Bootstrap...

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 control-plane to see this node join the cluster.

Finally, the master node views nodes: (the final cluster information is as follows)

[root@k8smaster1 ~]# kubectl get nodes
k8smaster1   NotReady   master   69m    v1.18.0
k8snode1     NotReady   <none>   49m    v1.18.0
k8snode2     NotReady   <none>   4m7s   v1.18.0

The status is not ready, and the network plug-in needs to be installed

 4. Deploy CNI network plug-in

Modify the sed command to docker hub image warehouse, and execute the following command on the master node.

kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

kubectl get pods -n kube-system

After the second command is executed, check the cluster status again after the relevant components are RUNNING

[root@k8smaster1 ~]# kubectl get pods -n kube-system
NAME                                 READY   STATUS    RESTARTS   AGE
coredns-7ff77c879f-stfqz             1/1     Running   0          106m
coredns-7ff77c879f-vhwr7             1/1     Running   0          106m
etcd-k8smaster1                      1/1     Running   0          107m
kube-apiserver-k8smaster1            1/1     Running   0          107m
kube-controller-manager-k8smaster1   1/1     Running   0          107m
kube-flannel-ds-9bx4w                1/1     Running   0          5m31s
kube-flannel-ds-qzqjq                1/1     Running   0          5m31s
kube-flannel-ds-tldt5                1/1     Running   0          5m31s
kube-proxy-6vcvj                     1/1     Running   1          86m
kube-proxy-hn4gx                     1/1     Running   0          106m
kube-proxy-qzwh6                     1/1     Running   0          41m
kube-scheduler-k8smaster1            1/1     Running   0          107m
[root@k8smaster1 ~]# kubectl get nodes
k8smaster1   Ready    master   107m   v1.18.0
k8snode1     Ready    <none>   86m    v1.18.0
k8snode2     Ready    <none>   41m    v1.18.0

5. Test kubernetes cluster

kubectl create deployment nginx --image=nginx
kubectl expose deployment nginx --port=80 --type=NodePort
kubectl get pod,svc

The final generated information is as follows:

[root@k8smaster1 ~]# kubectl get pod,svc
NAME                        READY   STATUS    RESTARTS   AGE
pod/nginx-f89759699-cnj62   1/1     Running   0          3m5s

NAME                 TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)        AGE
service/kubernetes   ClusterIP      <none>        443/TCP        113m
service/nginx        NodePort   <none>        80:30951/TCP   2m40s

Test: it can be accessed from any host, and the port is 30951


View the docker processes of the three machines:

1. k8smaster

[root@k8smaster1 ~]# docker ps 
CONTAINER ID        IMAGE                                               COMMAND                  CREATED             STATUS              PORTS               NAMES
e71930a745f3        67da37a9a360                                        "/coredns -conf /etc..."   14 minutes ago      Up 14 minutes                           k8s_coredns_coredns-7ff77c879f-vhwr7_kube-system_9553d8cc-8efb-48d1-9790-4120e09869c7_0
5aaacb75700b        67da37a9a360                                        "/coredns -conf /etc..."   14 minutes ago      Up 14 minutes                           k8s_coredns_coredns-7ff77c879f-stfqz_kube-system_81bbe584-a3d1-413a-a785-d8edaca7b4c1_0
756d66c75a56        registry.aliyuncs.com/google_containers/pause:3.2   "/pause"                 14 minutes ago      Up 14 minutes                           k8s_POD_coredns-7ff77c879f-vhwr7_kube-system_9553d8cc-8efb-48d1-9790-4120e09869c7_0
658b02e25f89        registry.aliyuncs.com/google_containers/pause:3.2   "/pause"                 14 minutes ago      Up 14 minutes                           k8s_POD_coredns-7ff77c879f-stfqz_kube-system_81bbe584-a3d1-413a-a785-d8edaca7b4c1_0
8a6f86753098        404fc3ab6749                                        "/opt/bin/flanneld -..."   14 minutes ago      Up 14 minutes                           k8s_kube-flannel_kube-flannel-ds-qzqjq_kube-system_bf0155d2-0f27-492c-8029-2fe042869579_0
b047ca53a8fe        registry.aliyuncs.com/google_containers/pause:3.2   "/pause"                 14 minutes ago      Up 14 minutes                           k8s_POD_kube-flannel-ds-qzqjq_kube-system_bf0155d2-0f27-492c-8029-2fe042869579_0
3877168ddb09        43940c34f24f                                        "/usr/local/bin/kube..."   2 hours ago         Up 2 hours                              k8s_kube-proxy_kube-proxy-hn4gx_kube-system_fe8347ac-3c81-4cab-ba78-3da6ad598316_0
18a32d328d49        registry.aliyuncs.com/google_containers/pause:3.2   "/pause"                 2 hours ago         Up 2 hours                              k8s_POD_kube-proxy-hn4gx_kube-system_fe8347ac-3c81-4cab-ba78-3da6ad598316_0
5f62d3184cd7        303ce5db0e90                                        "etcd --advertise-cl..."   2 hours ago         Up 2 hours                              k8s_etcd_etcd-k8smaster1_kube-system_635d8dc817fc23c8a6c09070c81f668f_0
2af2a1b5d169        a31f78c7c8ce                                        "kube-scheduler --au..."   2 hours ago         Up 2 hours                              k8s_kube-scheduler_kube-scheduler-k8smaster1_kube-system_ca2aa1b3224c37fa1791ef6c7d883bbe_0
c77506ee4dd2        d3e55153f52f                                        "kube-controller-man..."   2 hours ago         Up 2 hours                              k8s_kube-controller-manager_kube-controller-manager-k8smaster1_kube-system_c4d2dd4abfffdee4d424ce839b0de402_0
303545e4eca9        74060cea7f70                                        "kube-apiserver --ad..."   2 hours ago         Up 2 hours                              k8s_kube-apiserver_kube-apiserver-k8smaster1_kube-system_ba7276261300df6a615a2d947d86d3fa_0
f9da54e2bfae        registry.aliyuncs.com/google_containers/pause:3.2   "/pause"                 2 hours ago         Up 2 hours                              k8s_POD_kube-scheduler-k8smaster1_kube-system_ca2aa1b3224c37fa1791ef6c7d883bbe_0
007e2a0cd10b        registry.aliyuncs.com/google_containers/pause:3.2   "/pause"                 2 hours ago         Up 2 hours                              k8s_POD_kube-controller-manager-k8smaster1_kube-system_c4d2dd4abfffdee4d424ce839b0de402_0
0666c8b43c32        registry.aliyuncs.com/google_containers/pause:3.2   "/pause"                 2 hours ago         Up 2 hours                              k8s_POD_kube-apiserver-k8smaster1_kube-system_ba7276261300df6a615a2d947d86d3fa_0
0ca472d7f2cd        registry.aliyuncs.com/google_containers/pause:3.2   "/pause"                 2 hours ago         Up 2 hours                              k8s_POD_etcd-k8smaster1_kube-system_635d8dc817fc23c8a6c09070c81f668f_0

2. k8sndoe1

[root@k8snode1 ~]# docker ps
CONTAINER ID        IMAGE                                               COMMAND                  CREATED             STATUS              PORTS               NAMES
8189b507fc4a        404fc3ab6749                                        "/opt/bin/flanneld -..."   10 minutes ago      Up 10 minutes                           k8s_kube-flannel_kube-flannel-ds-9bx4w_kube-system_aa9751c9-7dcf-494b-b720-606cb8950a6d_0
f8e8103639c1        43940c34f24f                                        "/usr/local/bin/kube..."   10 minutes ago      Up 10 minutes                           k8s_kube-proxy_kube-proxy-6vcvj_kube-system_55bc4b97-f479-4dd5-977a-2a61e0fce705_1
6675466fcc0e        registry.aliyuncs.com/google_containers/pause:3.2   "/pause"                 11 minutes ago      Up 10 minutes                           k8s_POD_kube-flannel-ds-9bx4w_kube-system_aa9751c9-7dcf-494b-b720-606cb8950a6d_0
51d248df0e8c        registry.aliyuncs.com/google_containers/pause:3.2   "/pause"                 11 minutes ago      Up 10 minutes                           k8s_POD_kube-proxy-6vcvj_kube-system_55bc4b97-f479-4dd5-977a-2a61e0fce705_1

3. k8snode2

[root@k8snode2 ~]# docker ps
CONTAINER ID        IMAGE                                                COMMAND                  CREATED             STATUS              PORTS               NAMES
d8bbbe754ebc        nginx                                                "/docker-entrypoint...."   4 minutes ago       Up 4 minutes                            k8s_nginx_nginx-f89759699-cnj62_default_9e3e4d90-42ac-4f41-9af7-f7939a52cb01_0
04fbdd617724        registry.aliyuncs.com/google_containers/pause:3.2    "/pause"                 7 minutes ago       Up 7 minutes                            k8s_POD_nginx-f89759699-cnj62_default_9e3e4d90-42ac-4f41-9af7-f7939a52cb01_0
e9dc459f9664        404fc3ab6749                                         "/opt/bin/flanneld -..."   15 minutes ago      Up 15 minutes                           k8s_kube-flannel_kube-flannel-ds-tldt5_kube-system_5b1ea760-a19e-4b5b-9612-6d9a6dda7f59_0
f1d0312d2308        registry.aliyuncs.com/google_containers/pause:3.2    "/pause"                 15 minutes ago      Up 15 minutes                           k8s_POD_kube-flannel-ds-tldt5_kube-system_5b1ea760-a19e-4b5b-9612-6d9a6dda7f59_0
d6bae886cb61        registry.aliyuncs.com/google_containers/kube-proxy   "/usr/local/bin/kube..."   About an hour ago   Up About an hour                        k8s_kube-proxy_kube-proxy-qzwh6_kube-system_7d72b4a8-c6ee-4982-9e88-df70d9745b2c_0
324507774c8e        registry.aliyuncs.com/google_containers/pause:3.2    "/pause"                 About an hour ago   Up About an hour                        k8s_POD_kube-proxy-qzwh6_kube-system_7d72b4a8-c6ee-4982-9e88-df70d9745b2c_0

You can see that the container of nginx runs on the k8snode2 node.


You can also use kubectl to view the operation

[root@k8smaster1 ~]# kubectl get pods -o wide
nginx-f89759699-cnj62   1/1     Running   0          10m   k8snode2   <none>           <none>

Output in yaml format:

[root@k8smaster1 ~]# kubectl get pods -o yaml 
apiVersion: v1
- apiVersion: v1
  kind: Pod
    creationTimestamp: "2022-01-09T03:49:49Z"
    generateName: nginx-f89759699-
      app: nginx
. . . 

View all pods related and output details under all namespace s

[root@k8smaster1 ~]# kubectl get pods --all-namespaces -o wide
NAMESPACE              NAME                                         READY   STATUS    RESTARTS   AGE    IP               NODE         NOMINATED NODE   READINESS GATES
default                nginx-f89759699-cnj62                        1/1     Running   0          51m       k8snode2     <none>           <none>
kube-system            coredns-7ff77c879f-stfqz                     1/1     Running   0          161m       k8smaster1   <none>           <none>
kube-system            coredns-7ff77c879f-vhwr7                     1/1     Running   0          161m       k8smaster1   <none>           <none>
kube-system            etcd-k8smaster1                              1/1     Running   0          161m   k8smaster1   <none>           <none>
kube-system            kube-apiserver-k8smaster1                    1/1     Running   0          161m   k8smaster1   <none>           <none>
kube-system            kube-controller-manager-k8smaster1           1/1     Running   0          161m   k8smaster1   <none>           <none>
kube-system            kube-flannel-ds-9bx4w                        1/1     Running   0          59m   k8snode1     <none>           <none>
kube-system            kube-flannel-ds-qzqjq                        1/1     Running   0          59m   k8smaster1   <none>           <none>
kube-system            kube-flannel-ds-tldt5                        1/1     Running   0          59m   k8snode2     <none>           <none>
kube-system            kube-proxy-6vcvj                             1/1     Running   1          140m   k8snode1     <none>           <none>
kube-system            kube-proxy-hn4gx                             1/1     Running   0          161m   k8smaster1   <none>           <none>
kube-system            kube-proxy-qzwh6                             1/1     Running   0          95m   k8snode2     <none>           <none>
kube-system            kube-scheduler-k8smaster1                    1/1     Running   0          161m   k8smaster1   <none>           <none>
kubernetes-dashboard   dashboard-metrics-scraper-78f5d9f487-sfjlr   1/1     Running   0          25m       k8snode2     <none>           <none>
kubernetes-dashboard   kubernetes-dashboard-577bd97bc-f2v5g         1/1     Running   0          25m       k8snode1     <none>           <none>


Add: when the master executes kubedm init initialization, the following local errors are reported:

[kubelet-check] It seems like the kubelet isn't running or healthy.
[kubelet-check] The HTTP call equal to 'curl -sSL http://localhost:10248/healthz' failed with error: Get "http://localhost:10248/healthz": dial tcp [::1]:10248: connect: connection refused.

terms of settlement:

1. Create / etc / SYSTEMd / system / kubelet service. d/10-kubeadm. Conf file, as follows:

Environment="KUBELET_SYSTEM_PODS_ARGS=--pod-manifest-path=/etc/kubernetes/manifests --allow-privileged=true --fail-swap-on=false"

2. Restart kubelet

systemctl daemon-reload
systemctl restart kubelet

3. Re execute kubedm init

Add: the master # executes kubedm init for many times and reports the following errors:

error execution phase preflight: [preflight] Some fatal errors occurred:
        [ERROR FileAvailable--etc-kubernetes-manifests-kube-apiserver.yaml]: /etc/kubernetes/manifests/kube-apiserver.yaml already exists
        [ERROR FileAvailable--etc-kubernetes-manifests-kube-controller-manager.yaml]: /etc/kubernetes/manifests/kube-controller-manager.yaml already exists

This is because kubedm init was not cleaned up after the last execution. Solution:

kubeadm reset

Add: the master} executes kubedm init and reports the following error:

[kubelet-check] Initial timeout of 40s passed.

        Unfortunately, an error has occurred:
                timed out waiting for the condition

        This error is likely caused by:
                - The kubelet is not running
                - The kubelet is unhealthy due to a misconfiguration of the node in some way (required cgroups disabled)

        If you are on a systemd-powered system, you can try to troubleshoot the error with the following commands:
                - 'systemctl status kubelet'
                - 'journalctl -xeu kubelet'

It is said on the Internet that downloading some image warehouses timed out, and no relevant solutions were found. Finally, I deleted the virtual machine, re cloned a virtual machine, and then performed the above initialization and installation process.

Supplement: various errors are encountered in the master deployment process. Try installing different versions of kubedm, kubelet and kubectl

1. View the specified version:

yum list kubeadm --showduplicates

2. Delete related

yum remove -y kubelet kubeadm kubectl

3. Reinstall the specified version Yum install packagename version

yum install -y kubelet-1.17.0 kubeadm-1.17.0 kubectl-1.17.0

Add: after the node joins the k8s cluster and starts, the network fails to start. The error is as follows

Failed to start LSB 

terms of settlement:

1. Shut down the NetworkManager service

systemctl stop NetworkManager
systemctl disable NetworkManager

2. Restart

systemctl restart network


Keywords: Kubernetes

Added by vivianp79 on Sun, 09 Jan 2022 10:06:24 +0200