Deploy a sample application on Linux
In this topic, you deploy a sample application to your cluster on linux nodes.
Prerequisites
-
An existing Kubernetes cluster with at least one node. If you don’t have an existing Amazon EKS cluster, you can deploy one using one of the guides in Get started with Amazon EKS.
-
Kubectl
installed on your computer. For more information, see Set up kubectl and eksctl. -
Kubectl
configured to communicate with your cluster. For more information, see Connect kubectl to an EKS cluster by creating a kubeconfig file. -
If you plan to deploy your sample workload to Fargate, then you must have an existing Fargate profile that includes the same namespace created in this tutorial, which is
eks-sample-app
, unless you change the name. If you created a cluster with one of the gudes in Get started with Amazon EKS, then you’ll have to create a new profile, or add the namespace to your existing profile, because the profile created in the getting started guides doesn’t specify the namespace used in this tutorial. Your VPC must also have at least one private subnet.
Though many variables are changeable in the following steps, we recommend only changing variable values where specified. Once you have a better understanding of Kubernetes Pods, deployments, and services, you can experiment with changing other values.
Create a namespace
A namespace allows you to group resources in Kubernetes. For more information, see Namespacesnamespace
in your Define which Pods use AWS Fargate when launched is eks-sample-app
.
kubectl create namespace eks-sample-app
Create a Kubernetes deployment
Create a Kubernetes deployment. This sample deployment pulls a container image from a public repository and deploys three replicas (individual Pods) of it to your cluster. To learn more, see Deployments
-
Save the following contents to a file named
eks-sample-deployment.yaml
. The containers in the sample application don’t use network storage, but you might have applications that need to. For more information, see Store application data for your cluster.-
The
amd64
orarm64
values
under thekubernetes.io/arch
key mean that the application can be deployed to either hardware architecture (if you have both in your cluster). This is possible because this image is a multi-architecture image, but not all are. You can determine the hardware architecture that the image is supported on by viewing the image detailsin the repository that you’re pulling it from. When deploying images that don’t support a hardware architecture type, or that you don’t want the image deployed to, remove that type from the manifest. For more information, see Well-Known Labels, Annotations and Taints in the Kubernetes documentation. -
The
kubernetes.io/os: linux
nodeSelector
means that if you had Linux and Windows nodes (for example) in your cluster, the image would only be deployed to Linux nodes. For more information, see Well-Known Labels, Annotations and Taintsin the Kubernetes documentation. apiVersion: apps/v1 kind: Deployment metadata: name: eks-sample-linux-deployment namespace: eks-sample-app labels: app: eks-sample-linux-app spec: replicas: 3 selector: matchLabels: app: eks-sample-linux-app template: metadata: labels: app: eks-sample-linux-app spec: affinity: nodeAffinity: requiredDuringSchedulingIgnoredDuringExecution: nodeSelectorTerms: - matchExpressions: - key: kubernetes.io/arch operator: In values: - amd64 - arm64 containers: - name: nginx image: public.ecr.aws/nginx/nginx:1.23 ports: - name: http containerPort: 80 imagePullPolicy: IfNotPresent nodeSelector: kubernetes.io/os: linux
-
-
Apply the deployment manifest to your cluster.
kubectl apply -f eks-sample-deployment.yaml
Create a service
A service allows you to access all replicas through a single IP address or name. For more information, see Service
-
Save the following contents to a file named
eks-sample-service.yaml
. Kubernetes assigns the service its own IP address that is accessible only from within the cluster. To access the service from outside of your cluster, deploy the AWS Load Balancer Controller to load balance application or network traffic to the service.apiVersion: v1 kind: Service metadata: name: eks-sample-linux-service namespace: eks-sample-app labels: app: eks-sample-linux-app spec: selector: app: eks-sample-linux-app ports: - protocol: TCP port: 80 targetPort: 80
-
Apply the service manifest to your cluster.
kubectl apply -f eks-sample-service.yaml
Review resources created
-
View all resources that exist in the
eks-sample-app
namespace.kubectl get all -n eks-sample-app
An example output is as follows.
NAME READY STATUS RESTARTS AGE pod/eks-sample-linux-deployment-65b7669776-m6qxz 1/1 Running 0 27m pod/eks-sample-linux-deployment-65b7669776-mmxvd 1/1 Running 0 27m pod/eks-sample-linux-deployment-65b7669776-qzn22 1/1 Running 0 27m NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE service/eks-sample-linux-service ClusterIP 10.100.74.8 <none> 80/TCP 32m NAME READY UP-TO-DATE AVAILABLE AGE deployment.apps/eks-sample-linux-deployment 3/3 3 3 27m NAME DESIRED CURRENT READY AGE replicaset.apps/eks-sample-linux-deployment-776d8f8fd8 3 3 3 27m
In the output, you see the service and deployment that were specified in the sample manifests deployed in previous steps. You also see three Pods. This is because
3
replicas
were specified in the sample manifest. For more information about Pods, see Podsin the Kubernetes documentation. Kubernetes automatically creates the replicaset
resource, even though it isn’t specified in the sample manifests. For more information aboutReplicaSets
, see ReplicaSetin the Kubernetes documentation. Note
Kubernetes maintains the number of replicas that are specified in the manifest. If this were a production deployment and you wanted Kubernetes to horizontally scale the number of replicas or vertically scale the compute resources for the Pods, use the Scale pod deployments with Horizontal Pod Autoscaler and the Adjust pod resources with Vertical Pod Autoscaler to do so.
-
View the details of the deployed service.
kubectl -n eks-sample-app describe service eks-sample-linux-service
An example output is as follows.
Name: eks-sample-linux-service Namespace: eks-sample-app Labels: app=eks-sample-linux-app Annotations: <none> Selector: app=eks-sample-linux-app Type: ClusterIP IP Families: <none> IP: 10.100.74.8 IPs: 10.100.74.8 Port: <unset> 80/TCP TargetPort: 80/TCP Endpoints: 192.168.24.212:80,192.168.50.185:80,192.168.63.93:80 Session Affinity: None Events: <none>
In the previous output, the value for
IP:
is a unique IP address that can be reached from any node or Pod within the cluster, but it can’t be reached from outside of the cluster. The values forEndpoints
are IP addresses assigned from within your VPC to the Pods that are part of the service. -
View the details of one of the Pods listed in the output when you viewed the namespace in a previous step. Replace
776d8f8fd8-78w66
with the value returned for one of your Pods.kubectl -n eks-sample-app describe pod eks-sample-linux-deployment-65b7669776-m6qxz
Abbreviated example output
Name: eks-sample-linux-deployment-65b7669776-m6qxz Namespace: eks-sample-app Priority: 0 Node: ip-192-168-45-132.us-west-2.compute.internal/192.168.45.132 [...] IP: 192.168.63.93 IPs: IP: 192.168.63.93 Controlled By: ReplicaSet/eks-sample-linux-deployment-65b7669776 [...] Conditions: Type Status Initialized True Ready True ContainersReady True PodScheduled True [...] Events: Type Reason Age From Message ---- ------ ---- ---- ------- Normal Scheduled 3m20s default-scheduler Successfully assigned eks-sample-app/eks-sample-linux-deployment-65b7669776-m6qxz to ip-192-168-45-132.us-west-2.compute.internal [...]
In the previous output, the value for
IP:
is a unique IP that’s assigned to the Pod from the CIDR block assigned to the subnet that the node is in. If you prefer to assign Pods IP addresses from different CIDR blocks, you can change the default behavior. For more information, see Deploy pods in alternate subnets with custom networking. You can also see that the Kubernetes scheduler scheduled the Pod on theNode
with the IP address192.168.45.132
.Tip
Rather than using the command line, you can view many details about Pods, services, deployments, and other Kubernetes resources in the AWS Management Console. For more information, see View Kubernetes resources in the AWS Management Console.
Run a shell on a Pod
-
Run a shell on the Pod that you described in the previous step, replacing
65b7669776-m6qxz
with the ID of one of your Pods.kubectl exec -it eks-sample-linux-deployment-65b7669776-m6qxz -n eks-sample-app -- /bin/bash
-
From the Pod shell, view the output from the web server that was installed with your deployment in a previous step. You only need to specify the service name. It is resolved to the service’s IP address by CoreDNS, which is deployed with an Amazon EKS cluster, by default.
curl eks-sample-linux-service
An example output is as follows.
<!DOCTYPE html> <html> <head> <title>Welcome to nginx!</title> [...]
-
From the Pod shell, view the DNS server for the Pod.
cat /etc/resolv.conf
An example output is as follows.
nameserver 10.100.0.10 search eks-sample-app.svc.cluster.local svc.cluster.local cluster.local us-west-2.compute.internal options ndots:5
In the previous output,
10.100.0.10
is automatically assigned as thenameserver
for all Pods deployed to the cluster. -
Disconnect from the Pod by typing
exit
. -
Once you’re finished with the sample application, you can remove the sample namespace, service, and deployment with the following command.
kubectl delete namespace eks-sample-app
Next Steps
After you deploy the sample application, you might want to try some of the following exercises: