> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Solution Deployments optional
> This lab article introduces Kubernetes deployments and guides through the process of setting up and validating deployments in a cluster.
In this lab article, you will be introduced to Kubernetes deployments. We will walk through each step of the process while ensuring that your cluster is correctly set up and that deployments function as expected.
## Step 1: Check the Initial Cluster State
Before creating any deployments, verify that your cluster has no existing pods, ReplicaSets, or deployments.
Start by checking for pods:
```bash theme={null}
controlplane ~ ➜ kubectl get pods
No resources found in default namespace.
```
Then, check for ReplicaSets:
```bash theme={null}
controlplane ~ ➜ kubectl get rs
No resources found in default namespace.
```
Finally, check for any deployments:
```bash theme={null}
controlplane ~ ➜ kubectl get deployments
No resources found in default namespace.
```
At this point, your environment is clean with zero pods, zero ReplicaSets, and zero deployments.
## Step 2: Observe Changes After a Deployment is Created
After applying some changes, check the deployments again. You should now see that one deployment exists:
```bash theme={null}
controlplane ~ ➜ kubectl get deployments
NAME READY UP-TO-DATE AVAILABLE AGE
frontend-deployment 0/4 4 0 10s
```
Examine the ReplicaSet created by that deployment:
```bash theme={null}
controlplane ~ ➜ kubectl get rs
NAME DESIRED CURRENT READY AGE
frontend-deployment-7f8dcd-b696 4 4 0 35s
```
And then inspect the pods:
```bash theme={null}
controlplane ~ ➜ kubectl get pods
NAME READY STATUS RESTARTS AGE
frontend-deployment-7f8dcd-b696-stmbx 0/1 ImagePullBackOff 0 59s
frontend-deployment-7f8dcd-b696-zc6x 0/1 ErrImagePull 0 59s
frontend-deployment-7f8dcd-b696-jgcbx 0/1 ErrImagePull 0 59s
frontend-deployment-7f8dcd-b696-jbr44 0/1 ErrImagePull 0 59s
```
Because none of the four pods are in a ready state, you need to identify which image they are trying to pull. Run the following command to display detailed information for one pod:
```bash theme={null}
kubectl describe pod frontend-deployment-7fd8cdb696-stmbx
```
From the output, notice that the specified image is `busybox:888`. Since this image does not exist, the pods are unable to reach a ready state.
The image name must be valid and available in your container registry. Verify the image tag before deployment to avoid issues like ImagePullBackOff.
## Step 3: Create a New Deployment Using a YAML Definition
### Verify Your Current Directory and Files
Ensure you are in the correct working directory and check the available files:
```bash theme={null}
controlplane ~ ➜ pwd
/root
controlplane ~ ➜ ls
deployment-definition-1.yaml sample.yaml
```
### Attempt to Create the Deployment
Run the following command to create the deployment from the YAML file:
```bash theme={null}
controlplane ~ ➜ kubectl create -f deployment-definition-1.yaml
```
If you encounter an error such as:
```bash theme={null}
Error from server (BadRequest): error when creating "deployment-definition-1.yaml": deployment in version "v1" cannot be handled as a Deployment: no kind "deployment" is registered for version "apps/v1" in scheme "k8s.io/apimachinery/v1.23.3-k3s1/pkg/runtime/scheme.go:100"
```
Open the file to correct the issue:
```bash theme={null}
controlplane ~ ➜ vi deployment-definition-1.yaml
```
### Update the Deployment YAML
The error is caused by incorrect casing in the kind field. The resource kind should be capitalized. Use the corrected YAML below:
```yaml theme={null}
apiVersion: apps/v1
kind: Deployment
metadata:
name: deployment-1
spec:
replicas: 2
selector:
matchLabels:
name: busybox-pod
template:
metadata:
labels:
name: busybox-pod
spec:
containers:
- name: busybox-container
image: busybox888
command:
- sh
- "-c"
- echo Hello Kubernetes! && sleep 3600
```
After saving the changes, create the deployment again:
```bash theme={null}
controlplane ~ ➜ kubectl create -f deployment-definition-1.yaml
```
## Step 4: Create a Deployment Using Command-Line Parameters
You can also create a deployment by specifying parameters directly in the command line. First, review the help for deployment creation:
```bash theme={null}
kubectl create deployment --help
```
For example, to create a deployment named `http-frontend` using a specified image with three replicas, run:
```bash theme={null}
kubectl create deployment http-frontend --image= --replicas=3
```
After executing the command, verify that the deployment and pods are running as expected:
```bash theme={null}
kubectl get deployments
```
Make sure that the `http-frontend` deployment reflects the desired number of replicas in the ready state.
## Final Validation
To ensure all deployments are functioning, validate by checking that all created deployments are running and the pods are in a ready state. This confirms that your environment is correctly configured and operational.
This concludes the lab article on Kubernetes deployments. In upcoming labs, you’ll explore additional Kubernetes functionalities to further enhance your skills.
## Links and References
* [Kubernetes Documentation](https://kubernetes.io/docs/)
* [Kubernetes Basics](https://kubernetes.io/docs/concepts/overview/what-is-kubernetes/)
* [Docker Hub](https://hub.docker.com/)
* [Terraform Registry](https://registry.terraform.io/)