Deployment ¶

Scenario:

• Modify Existing Deployment, e.g., add port number in below demo.

Demo:

Create Deployment nginx.

kubectl create deployment nginx --image=nginx

Execute command below to get yaml template with port number. The option --port=8080 specified the port that this container exposes.

kubectl create deployment nginx --image=nginx --port=8080 --dry-run=client -o yaml

Then we get to know the path to add port number, like below.

kubectl explain deployment.spec.template.spec.containers.ports.containerPort

Execute command below to edit the Deployemnt.

kubectl edit deployment nginx

Add below two lines to specify port number with 8080 and protocol is TCP.

spec:
  template:
    spec:
      containers:
      - image: nginx
        name: nginx
        ports:
        - containerPort: 8080
          protocol: TCP

Use command kubectl describe deployment <deployment_name>, we can see the port number was added.

Pod Template:
  Labels:  app=nginx
  Containers:
   nginx:
    Image:        nginx
    Port:         8080/TCP
    Host Port:    0/TCP
    Environment:  <none>
    Mounts:       <none>
  Volumes:        <none>

With command kubectl describe pod <pod_name>, we can see the port number was added.

Containers:
  nginx:
    Container ID:   containerd://af4a1243f981497074b5c006ac55fcf795688399871d1dfe91a095321f5c91aa
    Image:          nginx
    Image ID:       docker.io/library/nginx@sha256:1761fb5661e4d77e107427d8012ad3a5955007d997e0f4a3d41acc9ff20467c7
    Port:           8080/TCP
    Host Port:      0/TCP
    State:          Running
      Started:      Sun, 24 Jul 2022 22:50:12 +0800
    Ready:          True
    Restart Count:  0
    Environment:    <none>
    Mounts:
      /var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-hftdt (ro)

Info: Some key fields of deployment (use kubectl explain):

• deployment.spec.revisionHistoryLimit: The number of old ReplicaSets to retain to allow rollback. Defaults to 10.
• deployment.spec.strategy.type: Type of deployment. Can be Recreate or RollingUpdate. Default is RollingUpdate.
• deployment.spec.strategy.rollingUpdate.maxUnavailable: The maximum number of pods that can be unavailable during the update. Defaults to 25%.
• deployment.spec.strategy.rollingUpdate.maxSurge: The maximum number of pods that can be scheduled above the desired number of pods. Defaults to 25%. This can not be 0 if MaxUnavailable is 0.
• deployment.spec.minReadySeconds: Minimum number of seconds for which a newly created pod should be ready without any of its container crashing, for it to be considered available. Defaults to 0 (pod will be considered available as soon as it is ready).