Resource configuration format:
- apiVersion: The version used to define an api group.
- Kind: Used to define resource types.
- Metadata: Used to define metadata, what it contains, the name of a resource, its tags, the namespace to which it belongs, and so on.
- sepc:
- Used to define the expected state of a resource.
- status: The actual state of the resource, which the user cannot define, is maintained by k8s.
Get all the resource types supported by the cluster:
[root@k8smaster data]# kubectl api-resources NAME SHORTNAMES APIGROUP NAMESPACED KIND bindings true Binding componentstatuses cs false ComponentStatus configmaps cm true ConfigMap endpoints ep true Endpoints events ev true Event limitranges limits true LimitRange namespaces ns false Namespace nodes no false Node persistentvolumeclaims pvc true PersistentVolumeClaim persistentvolumes pv false PersistentVolume pods po true Pod podtemplates true PodTemplate replicationcontrollers rc true ReplicationController resourcequotas quota true ResourceQuota secrets true Secret serviceaccounts sa true ServiceAccount services svc true Service mutatingwebhookconfigurations admissionregistration.k8s.io false MutatingWebhookConfiguration validatingwebhookconfigurations admissionregistration.k8s.io false ValidatingWebhookConfiguration customresourcedefinitions crd,crds apiextensions.k8s.io false CustomResourceDefinition apiservices apiregistration.k8s.io false APIService controllerrevisions apps true ControllerRevision daemonsets ds apps true DaemonSet deployments deploy apps true Deployment replicasets rs apps true ReplicaSet statefulsets sts apps true StatefulSet tokenreviews authentication.k8s.io false TokenReview localsubjectaccessreviews authorization.k8s.io true LocalSubjectAccessReview selfsubjectaccessreviews authorization.k8s.io false SelfSubjectAccessReview selfsubjectrulesreviews authorization.k8s.io false SelfSubjectRulesReview subjectaccessreviews authorization.k8s.io false SubjectAccessReview horizontalpodautoscalers hpa autoscaling true HorizontalPodAutoscaler cronjobs cj batch true CronJob jobs batch true Job certificatesigningrequests csr certificates.k8s.io false CertificateSigningRequest leases coordination.k8s.io true Lease events ev events.k8s.io true Event daemonsets ds extensions true DaemonSet deployments deploy extensions true Deployment ingresses ing extensions true Ingress networkpolicies netpol extensions true NetworkPolicy podsecuritypolicies psp extensions false PodSecurityPolicy replicasets rs extensions true ReplicaSet ingresses ing networking.k8s.io true Ingress networkpolicies netpol networking.k8s.io true NetworkPolicy runtimeclasses node.k8s.io false RuntimeClass poddisruptionbudgets pdb policy true PodDisruptionBudget podsecuritypolicies psp policy false PodSecurityPolicy clusterrolebindings rbac.authorization.k8s.io false ClusterRoleBinding clusterroles rbac.authorization.k8s.io false ClusterRole rolebindings rbac.authorization.k8s.io true RoleBinding roles rbac.authorization.k8s.io true Role priorityclasses pc scheduling.k8s.io false PriorityClass csidrivers storage.k8s.io false CSIDriver csinodes storage.k8s.io false CSINode storageclasses sc storage.k8s.io false StorageClass volumeattachments storage.k8s.io false VolumeAttachment
Kubectl operation type:
- Declarative operation: Configure resources by command (create, delete...).
- Declarative operation: Write the configuration list in a file and let k8s apply the configuration in the file (kubectl apply -f xxx.yaml).
Official Operations Documentation: https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.16/
Create resources:
apply and create:
[root@k8smaster ~]# mkdir /data [root@k8smaster ~]# cd /data/ [root@k8smaster data]# vim develop-ns.yaml apiVersion: v1 kind: Namespace metadata: name: develop [root@k8smaster data]# kubectl create -f develop-ns.yaml namespace/develop created [root@k8smaster data]# kubectl get ns NAME STATUS AGE default Active 36d develop Active 31s kube-node-lease Active 36d kube-public Active 36d kube-system Active 36d [root@k8smaster data]# cp develop-ns.yaml sample-ns.yaml [root@k8smaster data]# vim sample-ns.yaml apiVersion: v1 kind: Namespace metadata: name: sample [root@k8smaster data]# kubectl apply -f sample-ns.yaml namespace/sample created [root@k8smaster data]# kubectl get ns NAME STATUS AGE default Active 36d develop Active 2m7s kube-node-lease Active 36d kube-public Active 36d kube-system Active 36d sample Active 4s [root@k8smaster data]# kubectl create -f develop-ns.yaml Error from server (AlreadyExists): error when creating "develop-ns.yaml": namespaces "develop" already exists [root@k8smaster data]# kubectl apply -f sample-ns.yaml namespace/sample unchanged
- create: You cannot duplicate the creation of an existing resource.
- Apply:apply configures for application, creates if resource does not exist, applies configuration of configuration manifest if resource is different from configuration manifest, can be applied repeatedly, and apply can apply all configuration files in one directory.
Output:
Output the configuration of the pod as a yaml template:
[root@k8smaster data]# kubectl get pods/nginx-deployment-6f77f65499-8g24d -o yaml --export Flag --export has been deprecated, This flag is deprecated and will be removed in future. apiVersion: v1 kind: Pod metadata: creationTimestamp: null generateName: nginx-deployment-6f77f65499- labels: app: nginx-deployment pod-template-hash: 6f77f65499 ownerReferences: - apiVersion: apps/v1 blockOwnerDeletion: true controller: true kind: ReplicaSet name: nginx-deployment-6f77f65499 uid: c22cc3e8-8fbe-420f-b517-5a472ba1ddef selfLink: /api/v1/namespaces/default/pods/nginx-deployment-6f77f65499-8g24d spec: containers: - image: nginx imagePullPolicy: Always name: nginx resources: {} terminationMessagePath: /dev/termination-log terminationMessagePolicy: File volumeMounts: - mountPath: /var/run/secrets/kubernetes.io/serviceaccount name: default-token-kk2fq readOnly: true dnsPolicy: ClusterFirst enableServiceLinks: true nodeName: k8snode1 priority: 0 restartPolicy: Always schedulerName: default-scheduler securityContext: {} serviceAccount: default serviceAccountName: default terminationGracePeriodSeconds: 30 tolerations: - effect: NoExecute key: node.kubernetes.io/not-ready operator: Exists tolerationSeconds: 300 - effect: NoExecute key: node.kubernetes.io/unreachable operator: Exists tolerationSeconds: 300 volumes: - name: default-token-kk2fq secret: defaultMode: 420 secretName: default-token-kk2fq status: phase: Pending qosClass: BestEffort
Run multiple containers:
[root@k8smaster data]# vim pod-demo.yaml apiVersion: v1 kind: Pod metadata: name: pod-demo namespace: default spec: containers: - name: bbox image: busybox:latest imagePullPolicy: IfNotPresent command: ["/bin/sh","-c","sleep 86400"] - name: myapp image: ikubernetes/myapp:v1 [root@k8smaster data]# kubectl apply -f pod-demo.yaml pod/pod-demo created [root@k8smaster data]# kubectl get pods NAME READY STATUS RESTARTS AGE myapp-deployment-558f94fb55-plk4v 1/1 Running 1 33d myapp-deployment-558f94fb55-rd8f5 1/1 Running 1 33d myapp-deployment-558f94fb55-zzmpg 1/1 Running 1 33d nginx-deployment-6f77f65499-8g24d 1/1 Running 1 33d pod-demo 2/2 Running 0 83s
Enter the container:
kubectl exec
- pod-demo:The name of the pod.
- -c: If there are more than one container in a pod, you need to specify the container name with-c to enter the specified container.
- -n: Specify the namespace.
- -it: interactive interface.
- --/bin/sh: Running shell.
[root@k8smaster data]# kubectl exec pod-demo -c bbox -n default -it -- /bin/sh / # ifconfig eth0 Link encap:Ethernet HWaddr DE:5A:59:84:21:8D inet addr:10.244.1.105 Bcast:0.0.0.0 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1450 Metric:1 RX packets:13 errors:0 dropped:0 overruns:0 frame:0 TX packets:1 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:978 (978.0 B) TX bytes:42 (42.0 B) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
_The IP in the bbox container is the IP of the Pod, and all the containers in a Pod are accessed by sharing an ip.
/ # netstat -tnl Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN / # ps aux PID USER TIME COMMAND 1 root 0:00 sleep 86400 6 root 0:00 /bin/sh 13 root 0:00 ps aux
_View through the netstat-tnl command that the container listens on port 80, which is obviously not the port in the bbox, but the port 80 of the myapp container.This proves that all containers in a Pod use a shared ip.
/ # wget -O - -q 127.0.0.1 #And when you access the local port, a page for myapp appears. Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a> / # exit
View the log of the specified container:
kubectl logs:
- pod-demo:The name of the pod.
- -c: If there are more than one container in a pod, you need to specify the container name with-c to enter the specified container.
- -n: Specify the namespace.
[root@k8smaster data]# kubectl logs pod-demo -n default -c myapp 127.0.0.1 - - [04/Dec/2019:06:36:04 +0000] "GET / HTTP/1.1" 200 65 "-" "Wget" "-" 127.0.0.1 - - [04/Dec/2019:06:36:11 +0000] "GET / HTTP/1.1" 200 65 "-" "Wget" "-" 127.0.0.1 - - [04/Dec/2019:06:36:17 +0000] "GET / HTTP/1.1" 200 65 "-" "Wget" "-"
Containers in Pod and node hosts share the same network:
_It is not recommended to use during production. If there are too many containers, port number conflicts may occur.
[root@k8smaster data]# vim host-pod.yaml apiVersion: v1 kind: Pod metadata: name: mypod namespace: default spec: containers: - name : myapp image: ikubernetes/myapp:v1 hostNetwork: true [root@k8smaster data]# kubectl apply -f host-pod.yaml pod/mypod created [root@k8smaster data]# kubectl get pods -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES myapp-deployment-558f94fb55-plk4v 1/1 Running 1 33d 10.244.2.94 k8snode2 <none> <none> myapp-deployment-558f94fb55-rd8f5 1/1 Running 1 33d 10.244.2.95 k8snode2 <none> <none> myapp-deployment-558f94fb55-zzmpg 1/1 Running 1 33d 10.244.1.104 k8snode1 <none> <none> mypod 1/1 Running 0 9s 192.168.43.176 k8snode2 <none> <none> nginx-deployment-6f77f65499-8g24d 1/1 Running 1 33d 10.244.1.103 k8snode1 <none> <none> pod-demo 2/2 Running 0 26m 10.244.1.105 k8snode1 <none> <none> [root@k8smaster data]# curl 192.168.43.176:80 Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>
hostPort:
[root@k8smaster data]# kubectl delete -f host-pod.yaml pod "mypod" deleted [root@k8smaster data]# vim host-pod.yaml #Map port 80 of the container to port 8080 of the host on which the container is running. apiVersion: v1 kind: Pod metadata: name: mypod namespace: default spec: containers: - name : myapp image: ikubernetes/myapp:v1 ports: - protocol: TCP containerPort: 80 name: http hostPort: 8080 [root@k8smaster data]# kubectl apply -f host-pod.yaml pod/mypod created [root@k8smaster data]# kubectl get pods -o wide #Discovering that myapp is running on the node2 node, we directly access port 8080 of node2. NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES myapp-deployment-558f94fb55-plk4v 1/1 Running 1 33d 10.244.2.94 k8snode2 <none> <none> myapp-deployment-558f94fb55-rd8f5 1/1 Running 1 33d 10.244.2.95 k8snode2 <none> <none> myapp-deployment-558f94fb55-zzmpg 1/1 Running 1 33d 10.244.1.104 k8snode1 <none> <none> mypod 1/1 Running 0 23s 10.244.2.96 k8snode2 <none> <none> nginx-deployment-6f77f65499-8g24d 1/1 Running 1 33d 10.244.1.103 k8snode1 <none> <none> pod-demo 2/2 Running 0 37m 10.244.1.105 k8snode1 <none> <none> [root@k8smaster data]# curl 192.168.43.176:8080 Hello MyApp | Version: v1 | <a href="hostname.html">Pod Name</a>
How Pod can be accessed externally:
- Containers/hostPort: Port mapping that maps the port of a container to the node host running the container.
- Host Network: Pod shares the same network with the local machine.
- Nodeport: A specific port is open on each node, and any traffic sent to that port is forwarded to the corresponding service, with ports ranging from 30000 to 32767.
Label:
_Labels are "key value" types of data that can be used to specify directly when a resource is created or to add active objects whenever needed, which can then be checked by a tag selector to complete the resource selection.
- An object can have more than one tag, and the same tag can be added to more than one resource.
- In practice, multiple labels of different latitudes can be attached to a resource to achieve flexible resource grouping management functions, such as version labels, environment labels, hierarchical architecture labels, etc., to cross-identify different versions, environments, and architecture levels of the same resource.
- A key name in a tag usually consists of a key prefix and a key name, where the key prefix is optional and is formatted like "KEY_PREFIX/KEY_NAME".
- Keys can use up to 63 characters, including letters, numbers, connection numbers, underscores, dots, and can only start with letters or numbers.
- The key prefix must be in DNS subdomain name format and cannot exceed 253 characters. When omitting the key prefix, the key will be treated as the user's private data. However, keys automatically added for user resources by k8s system components or third-party components must use the key prefix, while the "kubernetes.io/" prefix is reserved for use by the core components of kubernetes.
- The key value in a label must be no more than 63 characters. It must either be empty or begin and end with a letter or a number, with data using only letters, numbers, connection numbers, underscores, dots, and so on.
- rel: The released version.
- Stable: stable version.
- beta: beta.
- canary: canary version.
Label selector:
_Tag selectors are used to express query criteria or selection criteria for tags, and the Kubernetes API currently supports two selectors.
- Based on equality-based
- Operators are =, == and!=three, of which the first two have the same meaning, indicating an equivalence relationship and the last one an inequality relationship.
- set-based
- KEY in (Value1，Value2...)
- KEY not in (Vlaue1，Value2...)
- KEY: All resources that have this key name label.
- ! KEY: All resources that do not have this key name label.
_Logic to follow when using tag selection:
- The logical relationship between multiple selectors specified at the same time is an AND operation.
- Label selectors with null values mean that each resource object will be selected.
- An empty label selector will not be able to select any resources.
How to define the label selector:
Many resource objects of kubernetes must be associated with Pod resource objects in the form of label selectors, such as services, Deployment, and ReplicaSet-type resources. They use nested "selector" fields in spec fields, specify label selectors through "matchLabbels", or even support the use of "matchExpressions" to construct complex label selectors.System.
- matchLabels: Specify a label selector by directly giving a key-value pair.
- Match Expressions: A list of label selectors specified based on an expression, each of which is in the form of'{key:KEY_NAME, operator:OPERATOR,values:[VALUE1,VALUE2...]}', with Logic and Relationships between the selector lists.
- When using an In or NotIn operation, its value must not be an empty list of strings, but when using Exists or DostNotExist, its value must be empty.
Manage tags (create, modify, delete):
[root@k8smaster ~]# kubectl get pods --show-labels #View labels for pod resources. NAME READY STATUS RESTARTS AGE LABELS myapp-deployment-558f94fb55-plk4v 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 myapp-deployment-558f94fb55-rd8f5 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 myapp-deployment-558f94fb55-zzmpg 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 mypod 1/1 Running 1 45h <none> nginx-deployment-6f77f65499-8g24d 1/1 Running 2 35d app=nginx-deployment,pod-template-hash=6f77f65499 pod-demo 2/2 Running 2 46h <none> [root@k8smaster data]# vim pod-demo.yaml apiVersion: v1 kind: Pod metadata: name: pod-demo namespace: default labels: app: pod-demo #Define an app tag with a value of pod-demo. rel: stable #Define a rel tag, position stable. spec: containers: - name: bbox image: busybox:latest imagePullPolicy: IfNotPresent command: ["/bin/sh","-c","sleep 86400"] - name: myapp image: ikubernetes/myapp:v1 [root@k8smaster data]# kubectl apply -f pod-demo.yaml #Create labels. pod/pod-demo configured [root@k8smaster data]# kubectl get pods --show-labels NAME READY STATUS RESTARTS AGE LABELS myapp-deployment-558f94fb55-plk4v 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 myapp-deployment-558f94fb55-rd8f5 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 myapp-deployment-558f94fb55-zzmpg 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 mypod 1/1 Running 1 46h <none> nginx-deployment-6f77f65499-8g24d 1/1 Running 2 35d app=nginx-deployment,pod-template-hash=6f77f65499 pod-demo 2/2 Running 2 46h app=pod-demo,rel=stable [root@k8smaster data]# kubectl label pods pod-demo -n default tier=frontend #Use statements to add tags. pod/pod-demo labeled [root@k8smaster data]# kubectl get pods --show-labels NAME READY STATUS RESTARTS AGE LABELS myapp-deployment-558f94fb55-plk4v 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 myapp-deployment-558f94fb55-rd8f5 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 myapp-deployment-558f94fb55-zzmpg 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 mypod 1/1 Running 1 46h <none> nginx-deployment-6f77f65499-8g24d 1/1 Running 2 35d app=nginx-deployment,pod-template-hash=6f77f65499 pod-demo 2/2 Running 2 47h app=pod-demo,rel=stable,tier=frontend [root@k8smaster data]# kubectl label pods pod-demo -n default --overwrite app=myapp #Overwrite (modify) existing labels. pod/pod-demo labeled [root@k8smaster data]# kubectl get pods --show-labels NAME READY STATUS RESTARTS AGE LABELS myapp-deployment-558f94fb55-plk4v 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 myapp-deployment-558f94fb55-rd8f5 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 myapp-deployment-558f94fb55-zzmpg 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 mypod 1/1 Running 1 46h <none> nginx-deployment-6f77f65499-8g24d 1/1 Running 2 35d app=nginx-deployment,pod-template-hash=6f77f65499 pod-demo 2/2 Running 2 47h app=myapp,rel=stable,tier=frontend [root@k8smaster data]# kubectl label pods pod-demo -n default rel- #Delete the specified label by placing a minus sign after the label name. pod/pod-demo labeled [root@k8smaster data]# kubectl get pods --show-labels NAME READY STATUS RESTARTS AGE LABELS myapp-deployment-558f94fb55-plk4v 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 myapp-deployment-558f94fb55-rd8f5 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 myapp-deployment-558f94fb55-zzmpg 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 mypod 1/1 Running 1 46h <none> nginx-deployment-6f77f65499-8g24d 1/1 Running 2 35d app=nginx-deployment,pod-template-hash=6f77f65499 pod-demo 2/2 Running 2 47h app=myapp,tier=frontend
Filter resources using tags:
#View resources with label app equal to myapp. [root@k8smaster data]# kubectl get pods -n default -l app=myapp NAME READY STATUS RESTARTS AGE pod-demo 2/2 Running 2 47h
#View resources whose label app is not equal to myapp. [root@k8smaster data]# kubectl get pods -n default -l app!=myapp --show-labels NAME READY STATUS RESTARTS AGE LABELS myapp-deployment-558f94fb55-plk4v 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 myapp-deployment-558f94fb55-rd8f5 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 myapp-deployment-558f94fb55-zzmpg 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 mypod 1/1 Running 1 46h <none> nginx-deployment-6f77f65499-8g24d 1/1 Running 2 35d app=nginx-deployment,pod-template-hash=6f77f65499
#View resources labeled nginx-deployment and my app-deployment. [root@k8smaster data]# kubectl get pods -n default -l "app in (nginx-deployment,myapp-deployment)" --show-labels NAME READY STATUS RESTARTS AGE LABELS myapp-deployment-558f94fb55-plk4v 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 myapp-deployment-558f94fb55-rd8f5 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 myapp-deployment-558f94fb55-zzmpg 1/1 Running 2 35d app=myapp-deployment,pod-template-hash=558f94fb55 nginx-deployment-6f77f65499-8g24d 1/1 Running 2 35d app=nginx-deployment,pod-template-hash=6f77f65499
#-L: Output the app tag as a field [root@k8smaster data]# kubectl get pods -n default -l "app in (nginx-deployment,myapp-deployment)" -L app NAME READY STATUS RESTARTS AGE APP myapp-deployment-558f94fb55-plk4v 1/1 Running 2 35d myapp-deployment myapp-deployment-558f94fb55-rd8f5 1/1 Running 2 35d myapp-deployment myapp-deployment-558f94fb55-zzmpg 1/1 Running 2 35d myapp-deployment nginx-deployment-6f77f65499-8g24d 1/1 Running 2 35d nginx-deployment
#The view label app is not a resource for nginx-deployment and myapp-deployment. [root@k8smaster data]# kubectl get pods -n default -l "app notin (nginx-deployment,myapp-deployment)" -L app NAME READY STATUS RESTARTS AGE APP mypod 1/1 Running 1 47h pod-demo 2/2 Running 2 47h myapp
#View resources with app tags. [root@k8smaster data]# kubectl get pods -n default -l "app" -L app NAME READY STATUS RESTARTS AGE APP myapp-deployment-558f94fb55-plk4v 1/1 Running 2 35d myapp-deployment myapp-deployment-558f94fb55-rd8f5 1/1 Running 2 35d myapp-deployment myapp-deployment-558f94fb55-zzmpg 1/1 Running 2 35d myapp-deployment nginx-deployment-6f77f65499-8g24d 1/1 Running 2 35d nginx-deployment pod-demo 2/2 Running 2 47h myapp
#View resources that do not have app tags. [root@k8smaster data]# kubectl get pods -n default -l '!app' -L app NAME READY STATUS RESTARTS AGE APP mypod 1/1 Running 1 47h
Resource annotation:
_Comments are also "key value" type data, but they cannot be used for tagging and selecting kubernetes objects, only for providing "metadata" information to resources.
_Metadata in annotations is not limited by the number of characters, can be large or small, can be structured or unstructured, and supports the use of other characters that are prohibited in labels.
_When introducing new fields to a resource in a new version of kubernetes (Alpha or Beta phase), they are often provided as annotations to avoid confusing users with changes such as additions or deletions. Once support for their use is established, these new fields are introduced into the resource and the associated annotations are eliminated.
[root@k8smaster data]# vim pod-demo.yaml apiVersion: v1 kind: Pod metadata: name: pod-demo namespace: default labels: app: pod-demo rel: stable annotations: ik8s.io/project: hello spec: containers: - name: bbox image: busybox:latest imagePullPolicy: IfNotPresent command: ["/bin/sh","-c","sleep 86400"] - name: myapp image: ikubernetes/myapp:v1 [root@k8smaster data]# kubectl apply -f pod-demo.yaml pod/pod-demo configured [root@k8smaster data]# kubectl describe pods pod-demo -n default Name: pod-demo Namespace: default Priority: 0 Node: k8snode1/192.168.43.136 Start Time: Wed, 04 Dec 2019 14:20:01 +0800 Labels: app=pod-demo rel=stable tier=frontend Annotations: ik8s.io/project: hello kubectl.kubernetes.io/last-applied-configuration: {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{"ik8s.io/project":"hello"},"labels":{"app":"pod-demo","rel":"stable"},"name":"p... Status: Running IP: 10.244.1.106 IPs: <none>
Pod life cycle:
Status:
- Pending: The Pod has been accepted by the Kubernetes system, but one or more container mirrors have not been created and it will take time for the Pod and download mirrors to be scheduled before the Pod can run.
- Running: The Pod is bound to a node, all containers in the Pod have been created, at least one container is running, or is in a boot and restart state.
- Succeeded: All containers in the Pod are terminated successfully and will not be restarted.
- Failed: All containers in the Pod have terminated, and at least one container is the only failed termination.
- Unkonwn: The state of a Pod cannot be obtained for some reason, usually because the Pod fails to communicate with the host.
Pod start process:
- The user creates a Pod through a command or a yaml file and submits a request to the API Server.
- API Server stores information such as Pod's configuration in the etcd.
- API Server then notifies Scheduler of the Watch time.
- Scheduler uses a scheduling algorithm to select the target host.
- API Server then stores the dispatched host information in the etcd.
- API Server notifies the dispatching host Kubelet, Kubelet goes to etcd to read the configuration and attributes of the corresponding Pod, and then communicates these configuration and attribute information to the docker engine.
- The docker engine launches a container, and upon successful startup, the container's information is submitted to the API Server.
- API Server then saves the actual state of the Pod to etcd.
- Then, if the actual state and the expected state change, a series of collaborative work will occur between them.
- Complete the initialization of the container.
- Execute post start content after the main container starts.
- Probe after the main container is running (LiveinessProbe and ReadinessProbe).
Container probe:
- Liveness Probe: Indicates whether the container is running, if the Survival Probe fails, kubelet kills the container, and the container receives a restart policy. If the restart fails, the restart continues, and the restart interval increases in turn until it is specified as successful.If the container does not provide a survival probe, the default state is Success.
- ReadinessProbe: Indicates, oh, if it is ready for Service requests, if ready probing fails, the endpoint controller will remove the IP address of the Pod from all Service endpoints where the Pod matches. The ready state before the initial delay defaults to Failure, and the default state is Success if the container does not provide a ready probe.
Three processes for probes:
- ExecAction: Executes the specified command in a container and considers the diagnosis successful if the command exits with a return code of 0.
- HTTPGetAction: Performs an HTTP Get request on the container IP address on the specified port and path, and if the status code of the response is greater than or equal to 200 and less than 400, the diagnosis is considered successful.
- TCPSocketAction: Performs a TCP check on the IP address of a container on a specified port, and if the port is open, the diagnosis is considered successful.
Detection state structure:
- Success: The container passed the diagnosis.
- Failure: Container failed diagnosis.
- Unknown: Diagnosis failed, no action will be taken.
Health Status Detection LivenessProbe:
ExecAction instance:
_We create a check file by touch ing and use the test command to verify that the file exists and survives. After creating the file, the container sleeps for 30 seconds, and after 30 seconds the container deletes the file. At this time, the test command returns a result of 1, assuming the container is not alive, and a restart policy is applied to the container. After restarting, the container recreates the original file, and the test command returns 0 to confirm that the restart was successful.
[root@k8smaster data]# git clone https://github.com/iKubernetes/Kubernetes_Advanced_Practical.git Cloning into 'Kubernetes_Advanced_Practical'... remote: Enumerating objects: 489, done. remote: Total 489 (delta 0), reused 0 (delta 0), pack-reused 489 Receiving objects: 100% (489/489), 148.75 KiB | 110.00 KiB/s, done. Resolving deltas: 100% (122/122), done. [root@k8smaster chapter4]# cat liveness-exec.yaml apiVersion: v1 kind: Pod metadata: labels: test: liveness-exec name: liveness-exec spec: containers: - name: liveness-demo image: busybox args: - /bin/sh - -c - touch /tmp/healthy; sleep 30; rm -rf /tmp/healthy; sleep 600 livenessProbe: exec: command: - test - -e - /tmp/healthy [root@k8smaster chapter4]# kubectl describe pods liveness-exec Name: liveness-exec Namespace: default Priority: 0 Node: k8snode2/192.168.43.176 Start Time: Fri, 06 Dec 2019 15:27:55 +0800 Labels: test=liveness-exec Annotations: kubectl.kubernetes.io/last-applied-configuration: {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"labels":{"test":"liveness-exec"},"name":"liveness-exec","namespace":"default... Status: Running IP: 10.244.2.100 IPs: <none> Containers: liveness-demo: Container ID: docker://f91cec7c45f5a025e049b2d2e0b1dc15593e9c35f183a9a9aa8e09d40f22df4f Image: busybox Image ID: docker-pullable://busybox@sha256:24fd20af232ca4ab5efbf1aeae7510252e2b60b15e9a78947467340607cd2ea2 Port: <none> Host Port: <none> Args: /bin/sh -c touch /tmp/healthy; sleep 30; rm -rf /tmp/healthy; sleep 600 State: Running Started: Fri, 06 Dec 2019 15:28:02 +0800 Ready: True Restart Count: 0 #At this point the restart count is 0, wait 30 seconds, and we'll check again Liveness: exec [test -e /tmp/healthy] delay=0s timeout=1s period=10s #success=1 #failure=3 Environment: <none> Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-kk2fq (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: default-token-kk2fq: Type: Secret (a volume populated by a Secret) SecretName: default-token-kk2fq Optional: false QoS Class: BestEffort Node-Selectors: <none> Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s node.kubernetes.io/unreachable:NoExecute for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 43s default-scheduler Successfully assigned default/liveness-exec to k8snode2 Normal Pulling 42s kubelet, k8snode2 Pulling image "busybox" Normal Pulled 36s kubelet, k8snode2 Successfully pulled image "busybox" Normal Created 36s kubelet, k8snode2 Created container liveness-demo Normal Started 36s kubelet, k8snode2 Started container liveness-demo Warning Unhealthy 4s kubelet, k8snode2 Liveness probe failed: [root@k8smaster chapter4]# kubectl describe pods liveness-exec Name: liveness-exec Namespace: default Priority: 0 Node: k8snode2/192.168.43.176 Start Time: Fri, 06 Dec 2019 15:27:55 +0800 Labels: test=liveness-exec Annotations: kubectl.kubernetes.io/last-applied-configuration: {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"labels":{"test":"liveness-exec"},"name":"liveness-exec","namespace":"default... Status: Running IP: 10.244.2.100 IPs: <none> Containers: liveness-demo: Container ID: docker://96f7dfd4ef1df503152542fdd1336fd0153773fb7dde3ed32f4388566888d6f0 Image: busybox Image ID: docker-pullable://busybox@sha256:24fd20af232ca4ab5efbf1aeae7510252e2b60b15e9a78947467340607cd2ea2 Port: <none> Host Port: <none> Args: /bin/sh -c touch /tmp/healthy; sleep 30; rm -rf /tmp/healthy; sleep 600 State: Running Started: Fri, 06 Dec 2019 15:29:25 +0800 Last State: Terminated Reason: Error Exit Code: 137 Started: Fri, 06 Dec 2019 15:28:02 +0800 Finished: Fri, 06 Dec 2019 15:29:24 +0800 Ready: True Restart Count: 1 #A restart count of 1 was found. Liveness: exec [test -e /tmp/healthy] delay=0s timeout=1s period=10s #success=1 #failure=3 Environment: <none> Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-kk2fq (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: default-token-kk2fq: Type: Secret (a volume populated by a Secret) SecretName: default-token-kk2fq Optional: false QoS Class: BestEffort Node-Selectors: <none> Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s node.kubernetes.io/unreachable:NoExecute for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 2m25s default-scheduler Successfully assigned default/liveness-exec to k8snode2 Normal Killing 86s kubelet, k8snode2 Container liveness-demo failed liveness probe, will be restarted Normal Pulling 56s (x2 over 2m24s) kubelet, k8snode2 Pulling image "busybox" Normal Pulled 56s (x2 over 2m18s) kubelet, k8snode2 Successfully pulled image "busybox" Normal Created 56s (x2 over 2m18s) kubelet, k8snode2 Created container liveness-demo Normal Started 55s (x2 over 2m18s) kubelet, k8snode2 Started container liveness-demo Warning Unhealthy 6s (x5 over 106s) kubelet, k8snode2 Liveness probe failed: [root@k8smaster chapter4]# kubectl delete -f liveness-exec.yaml pod "liveness-exec" deleted
HTTPGetAction instance:
_After successful startup of the nginx container through postStart, we create a health check file in the root directory of the web page file, and then request the health check file through HTTPGet. If the request is successful, the service is considered healthy, otherwise the service is unhealthy.
[root@k8smaster chapter4]# cat liveness-http.yaml apiVersion: v1 kind: Pod metadata: labels: test: liveness name: liveness-http spec: containers: - name: liveness-demo image: nginx:1.12-alpine ports: - name: http containerPort: 80 lifecycle: postStart: exec: command: - /bin/sh - -c - 'echo Healty > /usr/share/nginx/html/healthz' livenessProbe: httpGet: path: /healthz port: http scheme: HTTP periodSeconds: 2 #Health examination interval 2 seconds failureThreshold: 2 #Error failures, no restart more than 2 times. initialDelaySeconds: 3 #Initialization delay, which waits 3 seconds for initialization after the container starts successfully [root@k8smaster chapter4]# kubectl get pods NAME READY STATUS RESTARTS AGE liveness-http 1/1 Running 0 23s myapp-deployment-558f94fb55-plk4v 1/1 Running 2 35d myapp-deployment-558f94fb55-rd8f5 1/1 Running 2 35d myapp-deployment-558f94fb55-zzmpg 1/1 Running 2 35d mypod 1/1 Running 1 2d1h nginx-deployment-6f77f65499-8g24d 1/1 Running 2 35d pod-demo 2/2 Running 2 2d2h [root@k8smaster chapter4]# kubectl describe pods liveness-http Name: liveness-http Namespace: default Priority: 0 Node: k8snode2/192.168.43.176 Start Time: Fri, 06 Dec 2019 16:28:26 +0800 Labels: test=liveness Annotations: kubectl.kubernetes.io/last-applied-configuration: {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"labels":{"test":"liveness"},"name":"liveness-http","namespace":"default"},"s... Status: Running IP: 10.244.2.101 IPs: <none> Containers: liveness-demo: Container ID: docker://cc2d4ad2e37ec04b0d629c15d3033ecf9d4ab7453349ab40def9eb8cfca28936 Image: nginx:1.12-alpine Image ID: docker-pullable://nginx@sha256:3a7edf11b0448f171df8f4acac8850a55eff30d1d78c46cd65e7bc8260b0be5d Port: 80/TCP Host Port: 0/TCP State: Running Started: Fri, 06 Dec 2019 16:28:27 +0800 Ready: True Restart Count: 0 #At this point the restart count is 0, we enter the container and test by deleting the check file artificially. Liveness: http-get http://:http/healthz delay=3s timeout=1s period=2s #success=1 #failure=2 Environment: <none> Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-kk2fq (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: default-token-kk2fq: Type: Secret (a volume populated by a Secret) SecretName: default-token-kk2fq Optional: false QoS Class: BestEffort Node-Selectors: <none> Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s node.kubernetes.io/unreachable:NoExecute for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 70s default-scheduler Successfully assigned default/liveness-http to k8snode2 Normal Pulling 70s kubelet, k8snode2 Pulling image "nginx:1.12-alpine" Normal Pulled 69s kubelet, k8snode2 Successfully pulled image "nginx:1.12-alpine" Normal Created 69s kubelet, k8snode2 Created container liveness-demo Normal Started 69s kubelet, k8snode2 Started container liveness-demo [root@k8smaster chapter4]# kubectl exec -it liveness-http -- /bin/sh / # cd /usr/share/nginx/html/ /usr/share/nginx/html # ls 50x.html healthz index.html /usr/share/nginx/html # rm -rf healthz /usr/share/nginx/html # exit [root@k8smaster chapter4]# kubectl exec -it liveness-http -- /bin/sh / # cd /usr/share/nginx/html/ /usr/share/nginx/html # ls 50x.html healthz index.html /usr/share/nginx/html # rm -rf healthz /usr/share/nginx/html # exit [root@k8smaster chapter4]# kubectl describe pods liveness-http Name: liveness-http Namespace: default Priority: 0 Node: k8snode2/192.168.43.176 Start Time: Fri, 06 Dec 2019 16:28:26 +0800 Labels: test=liveness Annotations: kubectl.kubernetes.io/last-applied-configuration: {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"labels":{"test":"liveness"},"name":"liveness-http","namespace":"default"},"s... Status: Running IP: 10.244.2.101 IPs: <none> Containers: liveness-demo: Container ID: docker://90f3016f707bcfc0e22c42dac54f4e4691e74db7fcc5d5d395f22c482c9ea704 Image: nginx:1.12-alpine Image ID: docker-pullable://nginx@sha256:3a7edf11b0448f171df8f4acac8850a55eff30d1d78c46cd65e7bc8260b0be5d Port: 80/TCP Host Port: 0/TCP State: Running Started: Fri, 06 Dec 2019 16:34:34 +0800 Last State: Terminated Reason: Completed Exit Code: 0 Started: Fri, 06 Dec 2019 16:28:27 +0800 Finished: Fri, 06 Dec 2019 16:34:33 +0800 Ready: True Restart Count: 1 #A restart count of 1 was found. Liveness: http-get http://:http/healthz delay=3s timeout=1s period=2s #success=1 #failure=2 Environment: <none> Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-kk2fq (ro) Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True Volumes: default-token-kk2fq: Type: Secret (a volume populated by a Secret) SecretName: default-token-kk2fq Optional: false QoS Class: BestEffort Node-Selectors: <none> Tolerations: node.kubernetes.io/not-ready:NoExecute for 300s node.kubernetes.io/unreachable:NoExecute for 300s Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 6m24s default-scheduler Successfully assigned default/liveness-http to k8snode2 Normal Pulling 6m24s kubelet, k8snode2 Pulling image "nginx:1.12-alpine" Normal Pulled 6m23s kubelet, k8snode2 Successfully pulled image "nginx:1.12-alpine" Warning Unhealthy 17s (x2 over 19s) kubelet, k8snode2 Liveness probe failed: HTTP probe failed with statuscode: 404 Normal Killing 17s kubelet, k8snode2 Container liveness-demo failed liveness probe, will be restarted Normal Pulled 17s kubelet, k8snode2 Container image "nginx:1.12-alpine" already present on machine Normal Created 16s (x2 over 6m23s) kubelet, k8snode2 Created container liveness-demo Normal Started 16s (x2 over 6m23s) kubelet, k8snode2 Started container liveness-demo [root@k8smaster chapter4]# kubectl exec -it liveness-http -- /bin/sh #Looking at the check file again, we found that it was created again. / # cd /usr/share/nginx/html/ /usr/share/nginx/html # ls 50x.html healthz index.html /usr/share/nginx/html # exit [root@k8smaster chapter4]# kubectl delete -f liveness-http.yaml pod "liveness-http" deleted
ReadinessProbe for Readiness State Detection:
ExecAction instance:
[root@k8smaster chapter4]# cat readiness-exec.yaml apiVersion: v1 kind: Pod metadata: labels: test: readiness-exec name: readiness-exec spec: containers: - name: readiness-demo image: busybox args: ["/bin/sh", "-c", "while true; do rm -f /tmp/ready; sleep 30; touch /tmp/ready; sleep 300; done"] readinessProbe: exec: command: ["test", "-e", "/tmp/ready"] initialDelaySeconds: 5 periodSeconds: 5 [root@k8smaster chapter4]# kubectl apply -f readiness-exec.yaml pod/readiness-exec created [root@k8smaster chapter4]# kubectl get pods NAME READY STATUS RESTARTS AGE myapp-deployment-558f94fb55-plk4v 1/1 Running 2 35d myapp-deployment-558f94fb55-rd8f5 1/1 Running 2 35d myapp-deployment-558f94fb55-zzmpg 1/1 Running 2 35d mypod 1/1 Running 1 2d1h nginx-deployment-6f77f65499-8g24d 1/1 Running 2 35d pod-demo 2/2 Running 2 2d2h readiness-exec 1/1 Running 0 57s root@k8smaster chapter4]# kubectl exec readiness-exec -- rm -f /tmp/ready [root@k8smaster chapter4]# kubectl get pods NAME READY STATUS RESTARTS AGE myapp-deployment-558f94fb55-plk4v 1/1 Running 2 35d myapp-deployment-558f94fb55-rd8f5 1/1 Running 2 35d myapp-deployment-558f94fb55-zzmpg 1/1 Running 2 35d mypod 1/1 Running 1 2d1h nginx-deployment-6f77f65499-8g24d 1/1 Running 2 35d pod-demo 2/2 Running 2 2d2h readiness-exec 0/1 Running 0 2m46s [root@k8smaster chapter4]# kubectl exec readiness-exec -- touch /tmp/ready [root@k8smaster chapter4]# kubectl get pods NAME READY STATUS RESTARTS AGE myapp-deployment-558f94fb55-plk4v 1/1 Running 2 35d myapp-deployment-558f94fb55-rd8f5 1/1 Running 2 35d myapp-deployment-558f94fb55-zzmpg 1/1 Running 2 35d mypod 1/1 Running 1 2d1h nginx-deployment-6f77f65499-8g24d 1/1 Running 2 35d pod-demo 2/2 Running 2 2d2h readiness-exec 1/1 Running 0 3m54s
Container restart policy:
_Pod objects may be terminated due to container program crashes or resource requests exceeding limits. Whether it should be rebuilt at this time depends on the definition of its restart policy attribute.
- Always: But restart the Pod object whenever it terminates. This is the default setting.
- OnFailure: Restart a Pod object only if it has an error.
- Never: Never restart.
Termination of Pod:
- The user requests to delete a Pod and submit it to the API Server.
- API Server records deletion information in etcd, but for grace reasons, deletion is not done immediately.
- After returning to the API Server, the API Server marks the Pod as a Terminating state and notifies the corresponding node of its kubelet.
- kubelet communicates with the docker engine, the docker engine terminates the corresponding container, and executes the contents of the pre-stop before the main container terminates. After running, the Docker engine stops the container and returns it to the API Server.
- API Server then notifies the endpoint controller (EndPoint Controller), which removes the Pod's information from the endpoint list, and then notifies the container process that if the grace period is exceeded, a KILL signal is sent to kill the container, which is then fed back to the API Server.
Restrict permissions on Pod (security context):
_The purpose of the Security Context is to limit the behavior of untrusted containers and to protect the system or other containers within the system from being affected by them.
K8s provides three ways to configure the Security Context:
- Container-level Security Context: Applies only to the specified container.
- Pod-level Security Context: Applies to all containers and volume s within a Pod.
- Pod Security Policies: Applies to all Pods and Volume s within a cluster.
Pod resource limit:
Container calculates the quota for resources:
- CPU is a compressable resource, that is, the resource quota can shrink on demand, while memory (currently) is an uncompressed resource.
- Measurement of CPU resources:
- One core corresponds to 1000 microcores, i.e. 1=1000m, 0.5=500m.
- Measurement of memory resources:
- The default unit is bytes, or you can use E, P, T, G, M, and K suffix units, or Ei, Pi, Ti, Gi, Mi, and Ki unit suffixes.
Restriction method:
- priorityClassName: Used to restrict Pod's priority in using operating system resources.
- resource: Used to limit Pod's use of resources such as cpu, memory, hard disk (upper-lower limit).
- limits: upper limit.
- requests: lower limit.
[root@k8smaster chapter4]# cat stress-pod.yaml apiVersion: v1 kind: Pod metadata: name: stress-pod spec: containers: - name: stress image: ikubernetes/stress-ng command: ["/usr/bin/stress-ng", "-c 1", "-m 1", "--metrics-brief"] resources: requests: memory: "128Mi" cpu: "200m" limits: memory: "512Mi" cpu: "400m" [root@k8smaster chapter4]# cat memleak-pod.yaml apiVersion: v1 kind: Pod metadata: name: memleak-pod spec: containers: - name: simmemleak image: saadali/simmemleak resources: requests: memory: "64Mi" cpu: "1" limits: memory: "64Mi" cpu: "1" [root@k8smaster chapter4]# kubectl apply -f memleak-pod.yaml pod/memleak-pod created [root@k8smaster chapter4]# kubectl get pods NAME READY STATUS RESTARTS AGE memleak-pod 0/1 ContainerCreating 0 6s myapp-deployment-558f94fb55-plk4v 1/1 Running 3 39d myapp-deployment-558f94fb55-rd8f5 1/1 Running 3 39d myapp-deployment-558f94fb55-zzmpg 1/1 Running 3 39d mypod 1/1 Running 2 6d nginx-deployment-6f77f65499-8g24d 1/1 Running 3 39d pod-demo 2/2 Running 4 6d1h readiness-exec 1/1 Running 1 3d22h [root@k8smaster chapter4]# kubectl describe memleak-pod Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 76s default-scheduler Successfully assigned default/memleak-pod to k8snode1 Normal Pulling 21s (x4 over 75s) kubelet, k8snode1 Pulling image "saadali/simmemleak" Normal Pulled 20s (x4 over 64s) kubelet, k8snode1 Successfully pulled image "saadali/simmemleak" Normal Created 20s (x4 over 64s) kubelet, k8snode1 Created container simmemleak Normal Started 20s (x4 over 64s) kubelet, k8snode1 Started container simmemleak Warning BackOff 9s (x7 over 62s) kubelet, k8snode1 Back-off restarting failed container #The boot will fail because we have given too little memory. [root@k8smaster chapter4]# kubectl describe pod memleak-pod | grep Reason Reason: CrashLoopBackOff Reason: OOMKilled #The startup failed because memory was exhausted. Type Reason Age From Message
Pod quality of service category:
_According to the requests and limits properties of the Pod object, Kubernetest classifies the Pod object into three quality of service (Quality of Service, QoS) categories: BestEffort, Burstable and Guaranteed:
- Guaranteed: Each Container Sets requests and limits attributes with the same value for CPU resources, and each container sets pod resources with requests and limits attributes with the same value for memory resources to be assigned to this category, which has the highest priority.
- Burstable: At least one container has the requests property of a CPU or memory resource set, but Pod resources that do not meet the Guaranteed category requirements automatically belong to this category, which has a medium priority.
- BestEffort: PD resources that do not have requests or limits properties set for any container automatically belong to this category, with their priority being the lowest.
[root@k8smaster chapter4]# kubectl get pods NAME READY STATUS RESTARTS AGE memleak-pod 0/1 CrashLoopBackOff 7 13m myapp-deployment-558f94fb55-plk4v 1/1 Running 3 39d myapp-deployment-558f94fb55-rd8f5 1/1 Running 3 39d myapp-deployment-558f94fb55-zzmpg 1/1 Running 3 39d mypod 1/1 Running 2 6d nginx-deployment-6f77f65499-8g24d 1/1 Running 3 39d pod-demo 2/2 Running 4 6d1h readiness-exec 1/1 Running 1 3d23h [root@k8smaster chapter4]# kubectl describe pod memleak-pod | grep QoS QoS Class: Guaranteed [root@k8smaster chapter4]# kubectl describe pod mypod | grep QoS QoS Class: BestEffort
Summary:
apiVersion，kind，metadata，spec，status(Read-only) #Required fields. spec: #Embedded field in spec. containers nodeSelector nodeName restartPolicy #Restart policy. Always，Never，OnFailure containers: name image imagePullPolicy: Alwasy,Never,IfNotPresent #Pull mirror policy. ports: name containerPort livenessProbe readinessProbe liftcycle ExecAction: exec TCPSocketAction: tcpSocket HTTPGetAction: httpGet