Essential Linux Commands for Kubernetes Practitioners

When working with Kubernetes, you'll often need to manipulate files, inspect logs, or debug containers using Linux commands. Here are the most frequently used ones I've encountered:

1. File Navigation & Inspection

pwd - Know Where You Are

pwd
# Output: /home/user/k8s-configs

ls - List Files Like a Pro

ls -lha /etc/kubernetes/  # Check Kubernetes config files
# -l = long format, -h = human-readable, -a = show hidden

find - Locate Files Quickly

find /var/log -name "*.log" -mtime -7  # Find recent logs

2. File Manipulation

cat/less - View File Contents

cat deployment.yaml       # Quick view
less /var/log/syslog      # Paginated view (press 'q' to quit)

grep - The Search Ninja

grep -r "image:" ./k8s/   # Find all container images in YAMLs
grep -i "error" /var/log/containers/*  # Case-insensitive error search

jq - JSON Wizardry (for K8s API responses)

kubectl get pods -o json | jq '.items[].metadata.name'

3. File Operations

curl - API & File Downloads

curl -LO https://storage.googleapis.com/minikube/releases/latest/minikube-linux-amd64

tar - Handle Archives

tar -xzvf helm-v3.12.0-linux-amd64.tar.gz  # Extract Helm

diff - Compare Files

diff -u old-deployment.yaml new-deployment.yaml

4. System & Process Management

ps - Process Inspection

ps aux | grep kubelet  # Check if kubelet is running

top/htop - Resource Monitoring

htop  # Interactive process viewer (install with `apt install htop`)

5. Networking

netstat/ss - Port Checking

ss -tulnp | grep 6443  # Check if Kubernetes API port is open

dig/nslookup - DNS Debugging

dig +short my-svc.default.svc.cluster.local  # Debug K8s DNS

6. Permission Management

chmod - Make Scripts Executable

chmod +x install-k8s-tools.sh

sudo - When You Need Superpowers

sudo systemctl restart kubelet  # Requires root

Practical Examples

1. Base64 for Kubernetes Secrets

# Encode
echo -n "secret-data" | base64
# Decode
echo "c2VjcmV0LWRhdGE=" | base64 --decode

2. Bulk Rename K8s Configs

for file in *.yaml; do mv "$file" "k8s-$file"; done

3. Count Running Pods from Logs

kubectl get pods | grep Running | wc -l

Pro Tips

1. Chain commands with | (pipe):

   cat /var/log/pods/* | grep "OOMKilled" | wc -l
   

2. Redirect outputs:

   kubectl describe node > node-details.txt 2>&1
   

3. Use watch for real-time monitoring:

   watch -n 2 'kubectl get pods | grep Pending'
   

Key Takeaway: Kubernetes runs on Linux. Mastering these commands will make you 10x more effective at debugging and automation.