Basic commands/operations in Kubernetes
All before learning how to perform with kubectl more efficiently, you should have at least a basic knowledge of what kubectl is and how it works. Moreover, if you're new to kubernetes then you must know "Beginner’s Guide To Setup Kubernetes" & "How To Access Kubernetes Dashboard Token". You can take an overview from our previous blogs.
Kubectl is a command-line interface that is used to run commands against the clusters of Kubernetes. It’s a CLI tool for the users through which you can communicate with the Kubernetes API server. Before running the command in the terminal, kubectl initially checks for the file name “config” and which you can see in the $HOME/.Kube directory. From a technical point of view, kubectl is a client for the Kubernetes API & from a user's point of view, it’s your cockpit to control the whole Kubernetes.
Kubectl syntax describes the command operations. To run the operations, kubectl includes the supported flags along with subcommands. And via this part of the Kubernetes series, we are going to render you some of the operations.
I. STARTING COMMANDS
1. Create
kubectl create −. kubectl create −. To run the operation we usually use the kubectl to create a command. To do this, JSON or YAML formats are accepted.
$ kubectl create -f file_name.yamlTo specify the resources with one or more files: -f file1 -f file2 -f file...
Below is the list through which we use to create multiple things by using the kubectl command.
deployment
namespace
quota
secret docker-registry
secret
secret generic
secret tls
serviceaccount
service clusterip
service loadbalancer
service nodeport
service nodeport2. Get
Display one or many resources, This command is capable of fetching data on the cluster about the Kubernetes resources.
List all pods in the ps output format.
$ kubectl get podsList all pods in ps output format with more information (such as node name).
$ kubectl get pods -o wideList a single replication controller with specified NAME in the ps output format.
$ kubectl get replicationcontroller web
List deployments in JSON output format, in the "v1" version of the "apps" API group:
$ kubectl get deployments.v1.apps -o jsonList a pod recognized by type and name specified in "pod.yaml" in the JSON output format.
$ kubectl get -f pod.yaml -o json3. Run
Create and run a particular image, possibly replicated.
Creates a deployment or job to manage the created container(s).
Start a single instance of nginx.
$ kubectl run nginx --image=nginx4. Expose
Expose a resource as a new Kubernetes service.
$ kubectl expose rc nginx --port=80 --target-port=80005. Delete
kubectl delete − Delete resources by filenames, stdin, resources and names, or by resources and label selector.
$ kubectl delete –f file_name/type_name --allDelete all pods
$ kubectl delete pods --allDelete pods and services with label name=myLabel.
$ kubectl delete pods,services -l name=myLabel
Delete a pod with minimal delay
II. APPLY MANAGEMENT
1. Apply
kubectl apply − It holds the capability to configure a resource by file or stdin.
$ kubectl apply –f filename2. Annotate
kubectl annotate − To attach metadata to Kubernetes objects, you can use either labels or annotations. As labels can be mostly used to opt the objects and to find collections of objects that satisfy certain conditions.
$ kubectl annotate created_object -f file_name resource-version _key = value
$ kubectl get pods pod_name --output=yaml3. Autoscale
kubectl autoscale − Autoscale is employed to auto-scale the pods which are specified as Deployment, replica set, Replication Controller. It also creates an autoscaler that automatically selects and sets the number of pods that runs in the Kubernetes cluster.
$ autoscale -f file_name/type [--min=MINPODS] --max=MAXPODS [--cpu-percent=CPU]
$ kubectl autoscale deployment foo --min=2 --max=10
4. Convert
Convert 'pod.yaml' to the most advanced version and print to stdout.
The command takes filename, directory, or URL as an input, and transforms it into the format of the version defined by --output-version flag. If the target version is not specified or not supported, convert to the latest version.
$ kubectl convert -f pod.yaml
5. kubectl edit − It is applied to end the resources on the server. This allows us to directly edit a resource that one can receive via the command-line tool.
$ kubectl edit Resource/Name | File Name6. Replace
Replace a resource by filename or stdin.
JSON and YAML formats are accepted. If replacing an existing resource, the complete resource spec must be provided. This can be obtained by
$ kubectl replace -f file_name7. Rollout
kubectl rollout − It is more competent in managing the rollout of deployment.
$ Kubectl rollout Sub_Command
$ kubectl rollout undo deployment/tomcatApart from the above, we can perform multiple tasks using the rollout such as
rollout history
View the rollout history of a deployment
$ kubectl rollout history deployment/abcrollout pause
the provided resource as paused
$ kubectl rollout pause deployment/nginxTo resume a paused resource.
$ kubectl rollout resumerollout resume
Resume a paused resource
$ kubectl rollout resume deployment/nginxrollout status
Watch the rollout status of a deployment
$ kubectl rollout status deployment/nginx
rollout undo
Rollback to the previous deployment
$ kubectl rollout undo deployment/abc8. Scale
kubectl scale − It will scale the dimension of Kubernetes Deployments, ReplicaSet, Replication Controller, or job.
$ kubectl scale –replica = 3 FILE_NAMEIII. WORK WITH APPS
1. cp
kubectl cp− Copy files and directories to and from containers.
$ kubectl cp Files_from_source Files_to_Destination
$ kubectl cp /tmp/foo -pod:/tmp/bar -c specific-container2. Describe
kubectl describe − Describes any appropriate resources in Kubernetes. Confers the details of a resource or an assortment of resources.
$ kubectl describe type type_nameDescribe a pod
$ kubectl describe pod/nginxDescribe a pod identified by type and name in "pod.json"
$ kubectl describe -f pod.jsonDescribe all pods
$ kubectl describe podsDescribe pods by label name=label_name
$ kubectl describe po -l name=label_name3. exec
kubectl exec− This helps to execute a command in the container.
$ kubectl exec POD -c container --command args
$ kubectl exec 123-5-456 date4. logs
They are employed to get the logs of the container in a pod. Printing the logs can be defining the container name in the pod. If the POD has only one container there is no need to define its name.
$ kubectl logs container_name
$ kubectl logs nginx5. port-forward
Forward one or more local ports to a pod. They are accepted to forward one or more local port to pods.
Listen on ports 5000 and 6000 locally, forwarding data to/from ports 5000 and 6000 in the pod
$ kubectl port-forward pod/mypod 5000 6000
$ kubectl port-forward tomcat 3000 4000
$ kubectl port-forward deployment/mydeployment 5000 60006. Top
kubectl top node − It displays CPU/Memory/Storage usage. The prime or the foremost command enables you to see the resource use for the nodes.
$ kubectl top node node_namepod
Display metrics for all pods in the default namespace
$ kubectl top podnode
Display metrics for all nodes
$ kubectl top node7. Attach
kubectl attach − Its major function is to attach things to the running container.
$ kubectl attach pod –c containersIV. CLUSTER MANAGEMENT
1. API-versions
kubectl API-versions − Basically, it prints the supported versions of API on the cluster.
$ kubectl api-version2. cluster-info
kubectl cluster-info − It represents the cluster Info.
Display addresses of the master and services with label kubernetes.io/cluster-service=true
Besides, debug and diagnose cluster problems, use 'kubectl cluster-info dump'.
$ kubectl cluster-infoDumps
Dumps cluster-info out suitable for debugging and diagnosing cluster problems. By default, dumps everything to stdout. You can optionally specify a directory with --output-directory. If you specify a directory, the Kubernetes will build an assortment of files in that directory.
By default only dumps things in the 'Kube-system' namespace, but you can shift to a different namespace with the --namespaces flag or specify --all-namespaces to dump all namespaces.
$ kubectl cluster-info dump --output-directory = /path/to/cluster-state3. Certificate
Modify certificate resources.
approve
Approve/Accept a certificate signing request.
$ kubectl approve -f file_name/typedeny
Deny a certificate signing request. This action represents a certificate signing controller to not to issue a certificate to the requestor.
$ kubectl deny -f file_name/type4. Drain
kubectl drain − This is used to drain a node for preservation purposes. It makes the node for maintenance. This will mark the node as unavailable so that it should not be indicated with a new container that will be created.
$ kubectl drain node_name –forceV. KUBECTL SETTINGS AND USAGE
1. Api-resources
Print the supported API Resources
$ kubectl api-resourcesPrint the supported API Resources with more information
$ kubectl api-resources -o wide2. config
current-context
kubectl config current-context − It displays the current context.
$ kubectl config current-contextdelete-cluster
kubectl config delete-cluster − Deletes the specified cluster from kubeconfig.
$ kubectl config delete-cluster cluster_namedelete-context
kubectl config delete-context − Deletes a specified context from kubeconfig.
$ kubectl config delete-context cluster_nameget-clusters
kubectl config get-clusters − Displays cluster defined in the kubeconfig.
$ kubectl config get-cluster
$ kubectl config get-cluster cluster_nameget-contexts
kubectl config get-contexts − Specifies one or many contexts. Displays one or many contexts from the kubeconfig file.
$ kubectl config get-context cluster_namerename-context
Renames a context from the kubeconfig file.
CONTEXT_NAME is the context name that you wish to change.
NEW_NAME is the new name you wish to set.
$ kubectl config rename-context old_name new_nameset
Sets a specific value in a kubeconfig file
PROPERTY_NAME is a dot delimited name where each token implies either an attribute name or a map key. Map keys may not include dots.
PROPERTY_VALUE is the new value you wish to set. Binary fields such as 'certificate-authority-data' expect a base64 encoded string unless the --set-raw-bytes flag is used.
$ kubectl config set PROPERTY_NAME PROPERTY_VALUE set-cluster
kubectl config set-cluster − Sets the cluster entry in Kubernetes.
Specifying a name that already exists will merge new fields on top of existing values for those fields.
$ kubectl config set-cluster --server=https://1.2.3.4
$ kubectl config set-cluster NAME [--server=server] [--certificate-authority=path/to/certificate/authority] [--insecure-skip-tls-verify=true]set-context
kubectl config set-context − Sets a context entry in kubernetes entrypoint. Clarifies a name that already exists will merge new fields on top of existing values for those fields.
$ kubectl config set-context NAME [--cluster = cluster_nickname] [--
user = user_nickname] [--namespace = namespace]
$ kubectl config set-context gce --user=cluster-adminset-credentials
kubectl config set-credentials − Sets a user entry in kubeconfig.
Specifying a name that already exists will merge new fields on top of existing values.
Bearer token flags: --token=bearer_token
Basic auth flags: --username=basic_user --password=basic_password
$ kubectl config set-credentials cluster-admin --username = name --
password = your_passwordunset
kubectl config unset − It unsets a specific component in kubectl. PROPERTY_NAME is a dot delimited name where each token represents either an attribute name or a map key. Map keys may not hold dots.
$ kubectl config unset PROPERTY_NAME PROPERTY_VALUEuse-context
kubectl config use-context − Sets the current context in kubectl file.
$ kubectl config use-context context_nameview
Display merged kubeconfig settings or a specified kubeconfig file.
You can use --output jsonpath={...} to extract specific values using a JSON path expression.
$ kubectl config view3. explain
Get the documentation of the resource and its fields
$ kubectl explain podsGet the documentation of a specific field of a resource
$ kubectl explain pods.spec.containers4. options
Print flags inherited by all commands
$ kubectl options5. version
Print the client and server versions for the current context
$ kubectl versionVI. DEPRECATED COMMANDS
1. Rolling
kubectl rolling-update − Operates a rolling update on a replication controller. Reinstates the specified replication controller with a new replication controller by updating a POD at a time.
$ kubectl rolling-update old_container_name new_container_name --
image = new_container_image| -f new_controller_spec
$ kubectl rolling-update frontend-v1 –f freontend-v2.yamlWhat’s Next
Kubectl syntax mentions the commands as we've explained in the foregoing section. Kubernetes is so profitable for the organizations' artistic team, for each of the projects, clarifies deployments, scalability, resilience, it also permits us to consume any underlying infrastructure and you know what it proffers you much to work upon. So let's call it Supernetes from today. Good luck and stay in touch!
PS: Besides we will guide you basic commands to deploy Nginx and Laravel Image on Kubernetes. To stay in touch and not miss any of our articles/blogs, then do subscribe to our newsletter, follow us on medium.com and check out our blog page https://blog.paradisetechsoft.com/.
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