# Kubernetes Deep Dive for DevOps Engineers

A comprehensive guide to Kubernetes concepts, kubectl commands, and productivity aliases for DevOps engineers.

## What is Kubernetes?

Kubernetes (K8s) is an open-source container orchestration platform that automates:

- **Deployment**: Rolling out containerized applications
- **Scaling**: Adjusting replicas based on demand
- **Management**: Self-healing, load balancing, service discovery
- **Configuration**: Managing secrets, configs, and environment variables

flowchart TB
    subgraph Control Plane
        API[API Server]
        ETCD[(etcd)]
        SCHED[Scheduler]
        CM[Controller Manager]
    end

    subgraph Worker Nodes
        subgraph Node1[Node 1]
            K1[Kubelet]
            KP1[Kube-proxy]
            P1[Pod]
            P2[Pod]
        end
        subgraph Node2[Node 2]
            K2[Kubelet]
            KP2[Kube-proxy]
            P3[Pod]
            P4[Pod]
        end
    end

    API --> ETCD
    API --> SCHED
    API --> CM
    API --> K1
    API --> K2

    style Control Plane fill:#e3f2fd,stroke:#1565c0
    style Node1 fill:#e8f5e9,stroke:#2e7d32
    style Node2 fill:#e8f5e9,stroke:#2e7d32
    style API fill:#fff3e0,stroke:#e65100
    style ETCD fill:#fce4ec,stroke:#c2185b

---

## Core Architecture

### Control Plane Components

| Component | Purpose |
| ------------------ | -------------------------------------------------------------------- |
| API Server | Frontend for the control plane; all communication goes through it |
| etcd | Distributed key-value store holding all cluster state |
| Scheduler | Assigns pods to nodes based on resource requirements and constraints |
| Controller Manager | Runs controllers (Deployment, ReplicaSet, Node, etc.) |
| Cloud Controller | Integrates with cloud provider APIs (load balancers, volumes, etc.) |

### Node Components

| Component | Purpose |
| ----------------- | ------------------------------------------------------------- |
| Kubelet | Agent on each node; ensures containers are running in pods |
| Kube-proxy | Network proxy maintaining network rules for pod communication |
| Container Runtime | Software running containers (containerd, CRI-O, Docker) |

### Key Resources

| Resource | Description | Use Case |
| ----------- | ------------------------------------------------ | ------------------------------------- |
| Pod | Smallest deployable unit; one or more containers | Running application containers |
| Deployment | Manages ReplicaSets and pod lifecycle | Stateless applications |
| Service | Stable network endpoint for pods | Load balancing, service discovery |
| ConfigMap | Non-sensitive configuration data | Environment variables, config files |
| Secret | Sensitive data (passwords, tokens) | Credentials, TLS certificates |
| Namespace | Virtual cluster for resource isolation | Multi-tenancy, environment separation |
| Ingress | HTTP/HTTPS routing to services | External access, TLS termination |
| StatefulSet | Manages stateful applications | Databases, message queues |
| DaemonSet | Ensures pod runs on all (or some) nodes | Log collectors, monitoring agents |
| Job/CronJob | Run-to-completion or scheduled tasks | Batch processing, backups |

---

## kubectl Command Reference

`kubectl` is the command-line tool for interacting with Kubernetes clusters. It communicates with the API server to manage resources.

### Basic Commands (Beginner)

These commands are for users just starting with Kubernetes.

| Command | Description | When to Use |
| -------- | -------------------------------------- | -------------------------------------------- |
| `create` | Create a resource from a file or stdin | Quick resource creation without full YAML |
| `expose` | Expose a resource as a new Service | Create a Service for existing Deployment/Pod |
| `run` | Run a particular image in the cluster | Quick testing, one-off containers |
| `set` | Set specific features on objects | Update image, resources, or env vars |

#### Beginner Command Examples

# Create a deployment from an image
kubectl create deployment nginx --image=nginx:latest

# Expose deployment as a service
kubectl expose deployment nginx --port=80 --type=ClusterIP

# Run a one-off pod for debugging
kubectl run debug --image=busybox --rm -it -- sh

# Update deployment image
kubectl set image deployment/nginx nginx=nginx:1.25

### Basic Commands (Intermediate)

Commands for day-to-day cluster interaction.

| Command | Description | When to Use |
| --------- | -------------------------------- | -------------------------------------------- |
| `explain` | Get documentation for a resource | Understanding resource fields and structure |
| `get` | Display one or many resources | Listing and viewing resources |
| `edit` | Edit a resource on the server | Quick modifications without re-applying YAML |
| `delete` | Delete resources | Removing resources from the cluster |

#### Intermediate Command Examples

# Get documentation for deployment spec
kubectl explain deployment.spec.replicas

# List all pods in current namespace
kubectl get pods

# List pods across all namespaces with extra info
kubectl get pods -A -o wide

# Edit a deployment in your default editor
kubectl edit deployment nginx

# Delete a pod
kubectl delete pod nginx-abc123

# Delete resources from a YAML file
kubectl delete -f deployment.yaml

### Deploy Commands

Commands for managing application deployments and scaling.

| Command | Description | When to Use |
| ----------- | ---------------------------------------------------- | --------------------------------------- |
| `rollout` | Manage the rollout of a resource | Check status, history, undo deployments |
| `scale` | Set a new size for Deployment/ReplicaSet/StatefulSet | Manual horizontal scaling |
| `autoscale` | Auto-scale based on CPU utilization | Set up Horizontal Pod Autoscaler |

#### Deploy Command Examples

# Check rollout status
kubectl rollout status deployment/nginx

# View rollout history
kubectl rollout history deployment/nginx

# Undo last rollout
kubectl rollout undo deployment/nginx

# Undo to specific revision
kubectl rollout undo deployment/nginx --to-revision=2

# Restart deployment (rolling restart)
kubectl rollout restart deployment/nginx

# Scale deployment to 5 replicas
kubectl scale deployment nginx --replicas=5

# Set up autoscaling (2-10 pods, target 50% CPU)
kubectl autoscale deployment nginx --min=2 --max=10 --cpu-percent=50

### Cluster Management Commands

Commands for cluster administration and node management.

| Command | Description | When to Use |
| -------------- | ----------------------------------- | ------------------------------------------- |
| `certificate` | Modify certificate resources | Managing TLS certificates |
| `cluster-info` | Display cluster information | Verify cluster connectivity and endpoints |
| `top` | Display resource usage (CPU/memory) | Monitoring resource consumption |
| `cordon` | Mark node as unschedulable | Preparing node for maintenance |
| `uncordon` | Mark node as schedulable | Returning node to service after maintenance |
| `drain` | Drain node for maintenance | Safely evict pods before node maintenance |
| `taint` | Update taints on nodes | Control pod scheduling to specific nodes |

#### Cluster Management Examples

# Show cluster info
kubectl cluster-info

# Show resource usage for nodes
kubectl top nodes

# Show resource usage for pods
kubectl top pods

# Cordon a node (no new pods scheduled)
kubectl cordon node-1

# Drain a node (evict pods, cordon)
kubectl drain node-1 --ignore-daemonsets --delete-emptydir-data

# Return node to service
kubectl uncordon node-1

# Add a taint to prevent scheduling
kubectl taint nodes node-1 key=value:NoSchedule

# Remove a taint
kubectl taint nodes node-1 key=value:NoSchedule-

### Troubleshooting and Debugging Commands

Essential commands for diagnosing issues.

| Command | Description | When to Use |
| -------------- | -------------------------------- | -------------------------------------------------- |
| `describe` | Show details of a resource | Investigating events, conditions, errors |
| `logs` | Print logs for a container | Debugging application issues |
| `attach` | Attach to a running container | Interactive debugging of running processes |
| `exec` | Execute a command in a container | Running commands inside containers |
| `port-forward` | Forward local ports to a pod | Local access to cluster services |
| `proxy` | Run a proxy to the API server | Accessing the API or dashboard locally |
| `cp` | Copy files to/from containers | Extracting logs, configs, or debugging data |
| `auth` | Inspect authorization | Checking RBAC permissions |
| `debug` | Create debugging sessions | Advanced troubleshooting with ephemeral containers |
| `events` | List events | Seeing what happened in the cluster |

#### Troubleshooting Examples

# Describe a pod (shows events, conditions, etc.)
kubectl describe pod nginx-abc123

# Get logs from a pod
kubectl logs nginx-abc123

# Follow logs in real-time
kubectl logs -f nginx-abc123

# Get logs from specific container in multi-container pod
kubectl logs nginx-abc123 -c sidecar

# Get logs from last hour
kubectl logs --since=1h nginx-abc123

# Execute command in pod
kubectl exec nginx-abc123 -- ls /etc/nginx

# Get interactive shell in pod
kubectl exec -it nginx-abc123 -- /bin/sh

# Port forward local 8080 to pod 80
kubectl port-forward pod/nginx-abc123 8080:80

# Port forward to a service
kubectl port-forward svc/nginx 8080:80

# Copy file from pod
kubectl cp nginx-abc123:/etc/nginx/nginx.conf ./nginx.conf

# Check if you can create pods
kubectl auth can-i create pods

# List all events sorted by time
kubectl get events --sort-by='.lastTimestamp'

# Debug a node with ephemeral container
kubectl debug node/node-1 -it --image=busybox

### Advanced Commands

Commands for advanced operations and GitOps workflows.

| Command | Description | When to Use |
| ----------- | -------------------------------------------------- | ---------------------------------------- |
| `diff` | Diff live version against would-be applied version | Preview changes before applying |
| `apply` | Apply configuration to a resource | Declarative resource management (GitOps) |
| `patch` | Update fields of a resource | Partial updates without full YAML |
| `replace` | Replace a resource by filename | Complete replacement of a resource |
| `wait` | Wait for a specific condition | Scripting, CI/CD pipelines |
| `kustomize` | Build a kustomization target | Kustomize-based deployments |

#### Advanced Command Examples

# Preview changes before applying
kubectl diff -f deployment.yaml

# Apply configuration (create or update)
kubectl apply -f deployment.yaml

# Apply all YAML files in a directory
kubectl apply -f ./k8s/

# Apply with kustomize
kubectl apply -k ./overlays/production/

# Patch a resource (strategic merge patch)
kubectl patch deployment nginx -p '{"spec":{"replicas":3}}'

# Patch using JSON patch
kubectl patch deployment nginx --type='json' -p='[{"op":"replace","path":"/spec/replicas","value":5}]'

# Wait for deployment to be ready
kubectl wait --for=condition=available deployment/nginx --timeout=60s

# Wait for pod to be ready
kubectl wait --for=condition=ready pod -l app=nginx --timeout=120s

# Build kustomization (dry-run)
kubectl kustomize ./overlays/production/

### Settings Commands

Commands for managing resource metadata and shell configuration.

| Command | Description | When to Use |
| ------------ | -------------------------------- | ---------------------------------------- |
| `label` | Update labels on a resource | Organizing resources, enabling selectors |
| `annotate` | Update annotations on a resource | Adding metadata, tool configuration |
| `completion` | Output shell completion code | Setting up tab completion |

#### Settings Command Examples

# Add a label to a pod
kubectl label pod nginx-abc123 environment=production

# Remove a label
kubectl label pod nginx-abc123 environment-

# Add annotation
kubectl annotate deployment nginx description="Web server"

# Set up zsh completion
source <(kubectl completion zsh)

---

## Shell Aliases Reference

These aliases are from the oh-my-zsh kubectl plugin. They dramatically speed up daily Kubernetes operations.

### Core Aliases

| Alias | Expands To | Description |
| ------- | -------------------------- | -------------------------------------- |
| `k` | `kubectl` | The foundation - shorthand for kubectl |
| `kaf` | `kubectl apply -f` | Apply a YAML file |
| `kapk` | `kubectl apply -k` | Apply a kustomization directory |
| `kca` | `kubectl --all-namespaces` | Run command across all namespaces |
| `kdel` | `kubectl delete` | Delete a resource |
| `kdelf` | `kubectl delete -f` | Delete resources from file |
| `kdelk` | `kubectl delete -k` | Delete kustomization resources |

### Context and Configuration

| Alias | Expands To | Description |
| ------ | -------------------------------------------------- | ----------------------------------------- |
| `kccc` | `kubectl config current-context` | Show current context |
| `kcgc` | `kubectl config get-contexts` | List all contexts |
| `kcuc` | `kubectl config use-context` | Switch to a different context |
| `kcsc` | `kubectl config set-context` | Modify a context |
| `kcdc` | `kubectl config delete-context` | Delete a context |
| `kcn` | `kubectl config set-context --current --namespace` | Set default namespace for current context |

### Pod Management

| Alias | Expands To | Description |
| -------- | ----------------------------------- | ------------------------------- |
| `kgp` | `kubectl get pods` | List pods in current namespace |
| `kgpa` | `kubectl get pods --all-namespaces` | List pods in all namespaces |
| `kgpall` | `kubectl get pods -A -o wide` | List all pods with node info |
| `kgpsl` | `kubectl get pods --show-labels` | List pods with their labels |
| `kdp` | `kubectl describe pods` | Describe a pod |
| `kep` | `kubectl edit pods` | Edit a pod |
| `kdelp` | `kubectl delete pods` | Delete a pod |
| `keti` | `kubectl exec -t -i` | Interactive exec into container |

### Service Management

| Alias | Expands To | Description |
| ------- | ---------------------------------- | ------------------------------- |
| `kgs` | `kubectl get svc` | List services |
| `kgsa` | `kubectl get svc --all-namespaces` | List services in all namespaces |
| `kds` | `kubectl describe svc` | Describe a service |
| `kes` | `kubectl edit svc` | Edit a service |
| `kdels` | `kubectl delete svc` | Delete a service |

### Deployment Management

| Alias | Expands To | Description |
| ------- | ------------------------------------ | ---------------------------------- |
| `kgd` | `kubectl get deployment` | List deployments |
| `kgda` | `kubectl get deployment -A` | List deployments in all namespaces |
| `kdd` | `kubectl describe deployment` | Describe a deployment |
| `ked` | `kubectl edit deployment` | Edit a deployment |
| `kdeld` | `kubectl delete deployment` | Delete a deployment |
| `ksd` | `kubectl scale deployment` | Scale a deployment |
| `krsd` | `kubectl rollout status deployment` | Check deployment rollout status |
| `krrd` | `kubectl rollout restart deployment` | Rolling restart a deployment |

### StatefulSet Management

| Alias | Expands To | Description |
| -------- | ------------------------------------- | ----------------------------------- |
| `kgss` | `kubectl get statefulset` | List statefulsets |
| `kgssa` | `kubectl get statefulset -A` | List statefulsets in all namespaces |
| `kdss` | `kubectl describe statefulset` | Describe a statefulset |
| `kess` | `kubectl edit statefulset` | Edit a statefulset |
| `kdelss` | `kubectl delete statefulset` | Delete a statefulset |
| `ksss` | `kubectl scale statefulset` | Scale a statefulset |
| `krsss` | `kubectl rollout status statefulset` | Check statefulset rollout status |
| `krrss` | `kubectl rollout restart statefulset` | Rolling restart a statefulset |

### DaemonSet Management

| Alias | Expands To | Description |
| -------- | ---------------------------- | --------------------------------- |
| `kgds` | `kubectl get daemonset` | List daemonsets |
| `kgdsa` | `kubectl get daemonset -A` | List daemonsets in all namespaces |
| `kdds` | `kubectl describe daemonset` | Describe a daemonset |
| `keds` | `kubectl edit daemonset` | Edit a daemonset |
| `kdelds` | `kubectl delete daemonset` | Delete a daemonset |

### ConfigMap and Secret Management

| Alias | Expands To | Description |
| --------- | ---------------------------- | --------------------------------- |
| `kgcm` | `kubectl get configmaps` | List configmaps |
| `kgcma` | `kubectl get configmaps -A` | List configmaps in all namespaces |
| `kdcm` | `kubectl describe configmap` | Describe a configmap |
| `kecm` | `kubectl edit configmap` | Edit a configmap |
| `kdelcm` | `kubectl delete configmap` | Delete a configmap |
| `kgsec` | `kubectl get secret` | List secrets |
| `kgseca` | `kubectl get secret -A` | List secrets in all namespaces |
| `kdsec` | `kubectl describe secret` | Describe a secret |
| `kdelsec` | `kubectl delete secret` | Delete a secret |

### Namespace Management

| Alias | Expands To | Description |
| -------- | ---------------------------- | -------------------- |
| `kgns` | `kubectl get namespaces` | List all namespaces |
| `kdns` | `kubectl describe namespace` | Describe a namespace |
| `kens` | `kubectl edit namespace` | Edit a namespace |
| `kdelns` | `kubectl delete namespace` | Delete a namespace |

### Node Management

| Alias | Expands To | Description |
| -------- | --------------------------------- | ---------------------- |
| `kgno` | `kubectl get nodes` | List all nodes |
| `kgnosl` | `kubectl get nodes --show-labels` | List nodes with labels |
| `kdno` | `kubectl describe node` | Describe a node |
| `keno` | `kubectl edit node` | Edit a node |
| `kdelno` | `kubectl delete node` | Delete a node |

### Ingress Management

| Alias | Expands To | Description |
| ------- | -------------------------- | -------------------------------- |
| `kgi` | `kubectl get ingress` | List ingresses |
| `kgia` | `kubectl get ingress -A` | List ingresses in all namespaces |
| `kdi` | `kubectl describe ingress` | Describe an ingress |
| `kei` | `kubectl edit ingress` | Edit an ingress |
| `kdeli` | `kubectl delete ingress` | Delete an ingress |

### PVC Management

| Alias | Expands To | Description |
| --------- | ---------------------- | ----------------------------- |
| `kgpvc` | `kubectl get pvc` | List persistent volume claims |
| `kgpvca` | `kubectl get pvc -A` | List PVCs in all namespaces |
| `kdpvc` | `kubectl describe pvc` | Describe a PVC |
| `kepvc` | `kubectl edit pvc` | Edit a PVC |
| `kdelpvc` | `kubectl delete pvc` | Delete a PVC |

### Job and CronJob Management

| Alias | Expands To | Description |
| -------- | -------------------------- | ------------------ |
| `kgj` | `kubectl get job` | List jobs |
| `kdj` | `kubectl describe job` | Describe a job |
| `kej` | `kubectl edit job` | Edit a job |
| `kdelj` | `kubectl delete job` | Delete a job |
| `kgcj` | `kubectl get cronjob` | List cronjobs |
| `kdcj` | `kubectl describe cronjob` | Describe a cronjob |
| `kecj` | `kubectl edit cronjob` | Edit a cronjob |
| `kdelcj` | `kubectl delete cronjob` | Delete a cronjob |

### Logs

| Alias | Expands To | Description |
| ------- | ---------------------------- | ---------------------------- |
| `klog` | `kubectl logs` | Get logs from a pod |
| `klf` | `kubectl logs -f` | Follow (tail) logs |
| `kl1h` | `kubectl logs --since 1h` | Logs from last hour |
| `kl1m` | `kubectl logs --since 1m` | Logs from last minute |
| `kl1s` | `kubectl logs --since 1s` | Logs from last second |
| `klf1h` | `kubectl logs --since 1h -f` | Follow logs from last hour |
| `klf1m` | `kubectl logs --since 1m -f` | Follow logs from last minute |
| `klf1s` | `kubectl logs --since 1s -f` | Follow logs from last second |

### Rollout Management

| Alias | Expands To | Description |
| ----- | ------------------------- | -------------------- |
| `krh` | `kubectl rollout history` | View rollout history |
| `kru` | `kubectl rollout undo` | Undo a rollout |

### Events

| Alias | Expands To | Description |
| ------ | ------------------------------------------------------- | -------------------------- |
| `kge` | `kubectl get events --sort-by=".lastTimestamp"` | List events sorted by time |
| `kgew` | `kubectl get events --sort-by=".lastTimestamp" --watch` | Watch events in real-time |

### All Resources

| Alias | Expands To | Description |
| ------ | -------------------- | ------------------------------------ |
| `kga` | `kubectl get all` | List all resources in namespace |
| `kgaa` | `kubectl get all -A` | List all resources in all namespaces |

### Utility

| Alias | Expands To | Description |
| ----- | ---------------------- | -------------------------------- |
| `kcp` | `kubectl cp` | Copy files to/from containers |
| `kpf` | `kubectl port-forward` | Port forward to a pod or service |

---

## Common Workflows

### Deploying an Application

# 1. Apply manifests
kaf deployment.yaml
kaf service.yaml

# 2. Check deployment status
krsd nginx

# 3. Watch pods come up
kgp -w

# 4. Check events if issues
kge

### Debugging a Failing Pod

# 1. Check pod status
kgp

# 2. Describe pod for events
kdp failing-pod-abc123

# 3. Check logs
klog failing-pod-abc123

# 4. If CrashLoopBackOff, check previous logs
klog failing-pod-abc123 --previous

# 5. Exec into container for investigation
keti failing-pod-abc123 -- /bin/sh

### Switching Between Environments

# List available contexts
kcgc

# Switch to production
kcuc production-cluster

# Verify
kccc

# Set default namespace
kcn production

### Rolling Update

# 1. Update image
kubectl set image deployment/nginx nginx=nginx:1.25

# 2. Watch rollout
krsd nginx

# 3. If issues, rollback
kru deployment/nginx

### Node Maintenance

# 1. Cordon the node
kubectl cordon node-1

# 2. Drain workloads
kubectl drain node-1 --ignore-daemonsets --delete-emptydir-data

# 3. Perform maintenance...

# 4. Return to service
kubectl uncordon node-1

---

## Best Practices

### Resource Management

1. **Always set resource requests and limits** - Prevents resource starvation
2. **Use namespaces** - Isolate teams, environments, or applications
3. **Label everything** - Enables filtering and selection

### Security

1. **Run as non-root** - Use `runAsNonRoot: true` in security context
2. **Drop capabilities** - Remove unnecessary Linux capabilities
3. **Use read-only filesystems** - Prevent runtime modifications
4. **Use Secrets, not ConfigMaps** - For sensitive data

### Deployments

1. **Use declarative YAML** - Store in git, use `kubectl apply`
2. **Set liveness and readiness probes** - Enable proper health checking
3. **Use rolling updates** - Minimize downtime during deployments
4. **Configure PodDisruptionBudgets** - Ensure availability during maintenance

### Debugging

1. **Check events first** - `kge` shows recent cluster activity
2. **Use describe** - Shows conditions, events, and configuration
3. **Check logs with context** - Use `--since` to limit log volume
4. **Use ephemeral containers** - For debugging without modifying pods

### Alias Usage Tips

1. **Memorize the pattern** - `k` + action (`g`et, `d`escribe, `del`ete) + resource (`p`od, `d`eployment, `s`ervice)
2. **Use tab completion** - Enable with `source <(kubectl completion zsh)`
3. **Combine with grep/jq** - `kgp | grep failing` or `k get pods -o json | jq`
4. **Use `-o wide`** - Add node information to output

---

## Quick Reference Card

CONTEXT & CONFIG
  kccc              current context
  kcgc              list contexts
  kcuc <ctx>        switch context
  kcn <ns>          set namespace

GET RESOURCES
  kgp               pods
  kgd               deployments
  kgs               services
  kgno              nodes
  kga               all resources
  kge               events

DESCRIBE & LOGS
  kdp <pod>         describe pod
  klog <pod>        get logs
  klf <pod>         follow logs

APPLY & DELETE
  kaf <file>        apply file
  kdelf <file>      delete from file

DEBUG
  keti <pod> -- sh  exec into pod
  kpf <pod> 8080:80 port forward
  kdp <pod>         describe (events)

DEPLOYMENTS
  krsd <deploy>     rollout status
  krrd <deploy>     restart deployment
  kru <deploy>      rollback
  ksd <deploy> --replicas=N  scale