What is a resource?
All the content in K8s is abstracted as resources, and after resources are instantiated, they are called objects.
List of resource types
Pod, ReplicaSet, Deployment, StatefulSet, DaemonSet, Job, CronJob (ReplicationController is deprecated in v1.11)
Service Discovery and Load Balancing
Service, Ingress …
ConfigMap, Secret, DownwardAPI
Namespace, Node, Role, ClusterRole, RoleBinding, ClusterRoleBinding
HPA, PodTemplate, LimitRange
List of resources
What is a resource manifest?
In K8S, we generally use yaml format files to create pods that meet our expected expectations, and such yaml files we generally call resource lists.
Resource list format
apiVersion: If no group name is given, then the default is croe, you can use kubectl api-versions to get all the apiVersion information on the current k8s version (each version may be different), or you can use kubectl explain resource name|grep VERSION to get the apiversion of the corresponding resource kind: resource category metadata: resource metadata spec: expected state (disired state) status: current state, this field is maintained by kubernetes itself and cannot be defined by the user
View list format
Take pod resources as an example, you can use the following command if you want to view the resource manifest format of pod resources.
You can only see the first level configuration with the above command. If you want to see the second level, such as metadata and spec, you can use the following command.
What is Namespace?
Namespace, also known as namespace, is a very important resource in the kubernetes system. Its main role is to enable resource isolation for multiple environments or multi-tenant resource isolation.
By default, all Pods in a kubernetes cluster are accessible to each other. However, in practice, you may not want two Pods to have access to each other, so you can divide them into different namespaces. kubernetes can form logical “groups” by assigning resources inside the cluster to different namespaces, so that the resources of different groups can be used and managed in isolation. Through the authorization mechanism of kubernetes, different namespaces can be given to different tenants for management, thus achieving multi-tenant resource isolation. At this point, you can also combine kubernetes’ resource quota mechanism to limit the resources that different tenants can occupy, such as CPU usage, memory usage, etc., to achieve the management of resources available to tenants.
List all namespaces
kubectl get ns
kubectl create ns dev
kubectl delete ns dev
kubectl create -f ns-dev.yaml
kubectl delete -f ns-dev.yaml
Resource management methods
- Command-based object management: use commands directly to manipulate kubernetes resources
- Command-based object configuration: manipulate kubernetes resources with command configuration and configuration files
- Declarative object configuration: manipulate kubernetes resources through apply command and configuration file
Command-based object management
The kubectl command is the command line tool for kubernetes centralized management, which enables the management of the cluster itself and the installation and deployment of containerized applications on the cluster. The command syntax is as follows:
comand: Specify the operation to be performed on the resource, such as create, get, delete type: specify the type of resource, such as deployment, pod, service name: specify the name of the resource, the name is case-sensitive flags: specifies additional optional parameters
|create||create a resource|
|edit||edit a resource|
|get||Get a resource|
|patch||update a resource|
|delete||delete a resource|
|explain||display a resource document|
|run||runs a specified image in the cluster|
|expose||expose a resource as a Service|
|describe||displays information about the resource’s internals|
|logs||export the container’s logs in the Pod|
|attach||to a running container|
|exec||execute a command in the container|
|cp||Copy files between Pods and inside and outside|
|rollout||manage the release of resources|
|scale||expands (scales) the number of Pods|
|autoscale||Automatically adjusts the number of Pods|
|apply||create or update a resource by file|
|label||Update the label on a resource|
|cluster-info||displays cluster information|
|version||displays the current version of the Client and Server|
Resource resource type, not listed here, as already mentioned above.
Command-based object configuration
Command-based object configuration is the use of commands in conjunction with a resource list
Once the resource manifest is created, use the following command
kubectl create -f resource list
kubectl get -f resource list
kubectl delete -f resource list
Declarative Object Configuration
Declarative object configuration is very similar to imperative object configuration, but it has only one command: apply.
The difference with imperative object configuration is that imperative is used to create and delete, while declarative is used to modify. When the resource list is modified, you can use the following command to update the resources.
kubectl apply -f resource list