Getting started with kubernetes command (namespaces, pods)

1 nameSpace Introduce

​ namespace The Chinese name of is namespace . You can think namespaces It's you kubernetes Virtualization in clusters . In a Kubernetes A cluster can have multiple namespaces , They are logically isolated from each other . Can provide you with organization , Help with safety and even performance ！

​ namespace An abstract collection of resources and objects , For example, it can be used to divide the objects in the system into different project groups or user groups . common pods, services, replication controllers and deployments All belong to a certain namespace Of （ The default is default）, and node, persistentVolumes And so on does not belong to any namespace.

​ Most of the Kubernetes By default, there will be a cluster called default Of namespace. actually , Should be 4 individual ：

​ 1,default： Your resources are created by default in default Namespace .

​ 2,kube-system：kubernetes System components use .

​ 3,kube-node-lease: kubernetes Cluster node lease status ,v1.13 Join in

​ 4,kube-public： Use of public resources . But it's not commonly used now .

​ This default （default） Of namespace It's nothing special , But you can't delete it . This is good for just starting to use kubernetes And some small product systems . However, it is not recommended to apply it to large-scale production systems . because , In this complex system , Teams can easily rewrite or interrupt other services unexpectedly or unconsciously service. contrary , Please create multiple namespaces to put your service( service ) Split into more manageable chunks .

​ effect ： In the case of multi tenancy , Realize resource isolation ： It belongs to logical isolation ; It belongs to the management boundary ; Not belonging to the network boundary ; For each namespace Make resource quotas .

1.1 View namespace

# Check the namespace spelling 
[[email protected] ~]# kubectl get namespaces
# View namespace abbreviations 
[[email protected] ~]# kubectl get ns

​ Check the... Under the namespace pod：

[[email protected] ~]# kubectl get pod --all-namespaces
[[email protected] ~]# kubectl get pod -A

​ The default namespace is as follows ：

default  User created pod Default in this namespace  
kube-public  All users can access , Include unauthenticated users  
kube-node-lease kubernetes Cluster node lease status ,v1.13 Join in  
kube-system kubernetes Clusters are using 

1.2 Create a namespace

[[email protected] ~]# kubectl create namespace dream21th-one
namespace/dream21th-one created
[[email protected] ~]# kubectl create ns dream21th-two
namespace/dream21th-two created
[[email protected] ~]# kubectl get ns
NAME              STATUS   AGE
default           Active   118d
dream21th-one     Active   49s
dream21th-two     Active   30s
kube-node-lease   Active   118d
kube-public       Active   118d
kube-system       Active   118d

1.3 Delete namespace

[[email protected] ~]# kubectl delete namespace dream21th-one
namespace "dream21th-one" deleted
[[email protected] ~]# kubectl delete ns dream21th-two
namespace "dream21th-two" deleted
[[email protected] ~]# kubectl get ns
NAME              STATUS   AGE
default           Active   118d
kube-node-lease   Active   118d
kube-public       Active   118d
kube-system       Active   118d

2 pod brief introduction

​ Pod yes kubernetes The smallest unit that the cluster can schedule .Pod It's the packaging of the container . stay Kubernetes In the cluster ,Pod It is the foundation of all business types , It's also K8S The smallest unit level of management , It is a combination of one or more containers . These containers share storage 、 Networks and namespaces , And how to run the specifications . stay Pod in , All containers are the same

I. arrangement and scheduling , And run in a shared context . For specific applications ,Pod Is their logical host ,Pod Contains multiple application containers related to business .

​ The Internet : every last Pod Will be assigned a unique Ip Address , stay Pod Each container in the shared network namespace , Include Ip Address and network port . In the same Pod The container in can be connected with localhost Communicate with each other . When Pod Containers in need of Pod When communicating with entities outside , You need to share network resources through ports, etc .

​ Storage :Pod A collection of shared storage volumes that can be specified , stay Pod All containers in the can access shared storage volumes , Allow these containers to share data . Storage volumes are also allowed in a Pod Persistent data , In case the container needs to be restarted .

​ K8s You don't usually create Pod. Instead, the controller and template configuration are used to manage and schedule the Pod Containers in may terminate and exit due to exceptions and other reasons ,kubernetes A restart strategy is provided to restart the container . The restart policy is for the same Pod All containers of work , The restart of the container is controlled by Node Upper kubelet perform .Pod Three restart strategies are supported , Pass... In the configuration file restartPolicy Field to set the restart policy （ Be careful , Restart here refers to Pod Host of Node Local restart on , Instead of dispatching to other Node On ）：

​ 1,Always： Just exit and restart ;

​ 2,OnFailure： Only if you fail to quit （exit code It's not equal to 0） when , Will restart ;

​ 3,Never： Just quit , No restart .

​ Kubernetes adopt cgroups Limiting the container CPU And computing resources like memory , Include requests（ request , The scheduler ensures that resources are sufficient Node On ） and limits（ ceiling ） etc. .

2.1 see pod

# see default Under the namespace pods
[[email protected] ~]# kubectl get pods
No resources found in default namespace.
# see kube-system Under the namespace pods
[[email protected] ~]# kubectl get pods -n kube-system
# View all namespaces pods
[[email protected] ~]# kubectl get pod --all-namespaces
[[email protected] ~]# kubectl get pod -A

2.2 establish pod

​ Download mirroring ：

[[email protected] ~]# docker pull tomcat:9.0.20-jre8-alpine

​ function pod：

# stay default Namespace pod Replica deployment
[[email protected] ~]# kubectl run tomcat9-test --image=tomcat:9.0.20-jre8-alpine --port=8080
kubectl run --generator=deployment/apps.v1 is DEPRECATED and will be removed in a future version. Use kubectl run --generator=run-pod/v1 or kubectl create instead.
deployment.apps/tomcat9-test created
[[email protected] ~]# kubectl get pod
NAME                            READY   STATUS    RESTARTS   AGE
tomcat9-test-569b5bf455-9bvzs   1/1     Running   0          14s
[[email protected] ~]# kubectl get pod -o wide
NAME                            READY   STATUS    RESTARTS   AGE   IP           NODE        NOMINATED NODE   READINESS GATES
tomcat9-test-569b5bf455-9bvzs   1/1     Running   0          22s   10.244.2.3   k8s-work2   <none>           <none>
# Use pod Of IP Access to the container 
[[email protected] ~]# curl 10.244.2.3:8080

2.3 Capacity expansion

#  Expand to 3 individual 
[[email protected] ~]# kubectl scale --replicas=3 deployment/tomcat9-test
deployment.apps/tomcat9-test scaled
#  see pod
[[email protected] ~]# kubectl get pod
NAME                            READY   STATUS              RESTARTS   AGE
tomcat9-test-569b5bf455-9bvzs   1/1     Running             0          4m17s
tomcat9-test-569b5bf455-s826c   0/1     ContainerCreating   0          5s
tomcat9-test-569b5bf455-zx4zk   0/1     ContainerCreating   0          5s
[[email protected] ~]# kubectl get pod -o wide
NAME                            READY   STATUS    RESTARTS   AGE     IP           NODE        NOMINATED NODE   READINESS GATES
tomcat9-test-569b5bf455-9bvzs   1/1     Running   0          4m22s   10.244.2.3   k8s-work2   <none>           <none>
tomcat9-test-569b5bf455-s826c   1/1     Running   0          10s     10.244.1.5   k8s-work1   <none>           <none>
tomcat9-test-569b5bf455-zx4zk   1/1     Running   0          10s     10.244.1.4   k8s-work1   <none>           <none>
# View deployment 
[[email protected] ~]# kubectl get deployment
NAME           READY   UP-TO-DATE   AVAILABLE   AGE
tomcat9-test   3/3     3            3           4m40s
[[email protected] ~]# kubectl get deployment -o wide
NAME           READY   UP-TO-DATE   AVAILABLE   AGE     CONTAINERS     IMAGES                      SELECTOR
tomcat9-test   3/3     3            3           4m52s   tomcat9-test   tomcat:9.0.20-jre8-alpine   run=tomcat9-test
[[email protected] ~]# curl 10.244.2.3:8080

2.4 Create services

[[email protected] ~]# kubectl expose deployment tomcat9-test --name=tomcat9-svc --port=8888 --target-port=8080 --protocol=TCP --type=NodePort
service/tomcat9-svc exposed
[[email protected] ~]# kubtck get pod
-bash: kubtck:  Command not found 
[[email protected] ~]# kubtck get pods
-bash: kubtck:  Command not found 
[[email protected] ~]# kubectl get pods
NAME                            READY   STATUS    RESTARTS   AGE
tomcat9-test-569b5bf455-9bvzs   1/1     Running   0          16m
tomcat9-test-569b5bf455-s826c   1/1     Running   0          12m
tomcat9-test-569b5bf455-zx4zk   1/1     Running   0          12m
[[email protected] ~]# kubtck get svc
-bash: kubtck:  Command not found 
[[email protected] ~]# kubectl get svc
NAME          TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)          AGE
kubernetes    ClusterIP   10.96.0.1     <none>        443/TCP          118d
tomcat9-svc   NodePort    10.96.33.14   <none>        8888:30286/TCP   40s
[[email protected] ~]# curl 10.96.33.14:8888

​ Visit... On the browser http://192.168.43.103:30286/ It can also be accessed normally .

3 Commonly used instructions

3.1 get

​ kubectl get： List one or more resources .

# View the cluster status information 
[[email protected] ~]# kubectl cluster-info
[[email protected] ~]# kubectl get cs
NAME                 STATUS    MESSAGE             ERROR
controller-manager   Healthy   ok                  
scheduler            Healthy   ok                  
etcd-0               Healthy   {
    "health":"true"}  
# View the cluster node information 
[[email protected] ~]# kubectl get nodes
NAME         STATUS   ROLES    AGE    VERSION
k8s-master   Ready    master   118d   v1.17.5
k8s-work1    Ready    <none>   118d   v1.17.5
k8s-work2    Ready    <none>   118d   v1.17.5
#  View the cluster namespace 
[[email protected] ~]# kubectl get ns
#  View the services of the specified namespace 
[[email protected] ~]# kubectl get svc -n kube-system
#  List all... In plain text output format  pod.
[[email protected] ~]# kubectl get pods
#  List all... In plain text output format  pod, And include additional information ( Such as node roll call ).
[[email protected] ~]# kubectl get pods -o wide
#  Lists all replica controllers and services in plain text output format .
[[email protected] ~]# kubectl get rc,services
# List in node  server01  All of the  pod
[[email protected] ~]# kubectl get pods --field-selector=spec.nodeName=k9s-master

3.2 describe

​ kubectl describe - Displays the detailed status of one or more resources , Uninitialized resources are included by default .

[[email protected] ~]# kubectl describe nodes k8s-master
[[email protected] ~]# kubectl describe pods tomcat9-test-569b5bf455-9bvzs

3.3 delete

​ kubectl delete` - From file 、stdin Or specify a label selector 、 name 、 Delete a resource from the resource selector or resource .

#  Use  pod.yaml  Delete the type and name specified in the file  pod. 
kubectl delete -f pod.yaml 
#  Delete tag name = <label-name>  All of the  pod  And the service . 
kubectl delete pods,services -l name=<label-name> 
#  Delete all with tag names = <label-name>  Of  pod  And the service , Including those uninitialized . 
kubectl delete pods,services -l name=<label-name> --include-uninitialized 
#  Delete all  pod, Include uninitialized  pod. 
kubectl delete pods --all

3.4 Into the container

​ kubectl exec - Yes pod The container in executes the command . And docker Of exec The orders are very similar .

#  from  pod <pod-name>  Get run  'date'  Output . By default , The output comes from the first container . 
kubectl exec <pod-name> date
#  Operation output  'date'  Get the... In the container  <container-name>  in  pod <pod-name>  Output .
kubectl exec <pod-name> -c <container-name> date 
#  Get an interactive  TTY  And run  /bin/bash <pod-name >. By default , The output comes from the first container . 
kubectl exec -ti <pod-name> /bin/bash

3.5 logs

​ kubectl logs - Print Pod Log of the container in .

#  from  pod  Return to log snapshot . 
kubectl logs <pod-name> 
#  from  pod <pod-name>  Start streaming logs . This is similar to  'tail -f' Linux  command . 
kubectl logs -f <pod-name>

3.6 Format output

[[email protected] ~]# kubectl get pod tomcat9-test-569b5bf455-9bvzs -o yaml

3.7 Mandatory deletion pod

 Force the deletion of a pod 
--force --grace-period=0

4 Resource abbreviation