Linux Operations Skills

Versiones compatibles: Todas las distribuciones principales de Linux Última actualización: February 11, 2026

Este documento cubre habilidades esenciales de operaciones en Linux para trabajar eficazmente en entornos de Kubernetes.

---

Table of Contents

1. Environment Variables and Shell Configuration
2. Shell Scripting Basics
3. Text Processing Tools
4. SSH and Remote Access
5. Performance Monitoring and Troubleshooting
6. Storage Management Basics
7. curl and API Calls
8. Practical One-Liners Collection

---

1. Environment Variables and Shell Configuration

Las variables de entorno son el mecanismo central para gestionar la configuración en Linux y Kubernetes.

1.1 Environment Variable Basics

env
echo $HOME
echo $PATH
printenv HOME

1.2 The export Command

export MY_VAR="hello"
export DATABASE_URL="postgresql://localhost:5432/mydb"
export KUBECONFIG="/home/user/.kube/config"

1.3 The source Command

cat > ~/my-env.sh << 'SCRIPT'
export APP_ENV="production"
export APP_PORT="8080"
alias k='kubectl'
SCRIPT

source ~/my-env.sh

1.4 .bashrc and .bash_profile

cat >> ~/.bashrc << 'SCRIPT'
export KUBECONFIG=~/.kube/config
source <(kubectl completion bash)
alias k='kubectl'
SCRIPT

source ~/.bashrc

1.5 Kubernetes ConfigMap Connection

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  DATABASE_HOST: "mysql.default.svc.cluster.local"
  DATABASE_PORT: "3306"
---
apiVersion: v1
kind: Pod
metadata:
  name: app-pod
spec:
  containers:
  - name: app
    image: myapp:1.0
    envFrom:
    - configMapRef:
        name: app-config

---

2. Shell Scripting Basics

2.1 Variables

#!/bin/bash
NAME="kubernetes"
NAMESPACE=${1:-default}
: ${REQUIRED_VAR:?"REQUIRED_VAR must be set"}

2.2 Conditionals

if [ "$ENV" = "production" ]; then
    echo "Production mode"
fi

case "$1" in
    start) echo "Starting..." ;;
    stop) echo "Stopping..." ;;
esac

2.3 Loops

for ns in default kube-system monitoring; do
    kubectl get pods -n "$ns"
done

while true; do
    STATUS=$(kubectl get pod mypod -o jsonpath='{.status.phase}')
    [ "$STATUS" = "Running" ] && break
    sleep 5
done

2.4 Functions

check_pod_exists() {
    local pod_name=$1
    kubectl get pod "$pod_name" &>/dev/null
}

2.5 Init Container Patterns

apiVersion: v1
kind: Pod
metadata:
  name: app-with-init
spec:
  initContainers:
  - name: wait-for-db
    image: busybox:1.35
    command: ['sh', '-c', 'until nc -z mysql 3306; do sleep 2; done']
  containers:
  - name: app
    image: myapp:1.0

---

3. Text Processing Tools

3.1 grep with kubectl

kubectl get pods | grep -v "Running"
kubectl logs nginx-pod | grep -i error

3.2 awk Field Extraction

kubectl get pods | awk 'NR>1 {print $1}'
kubectl get pods | awk '$3 != "Running" {print $1, $3}'

3.3 sed Editing

sed -i 's/replicas: [0-9]*/replicas: 5/' deployment.yaml

3.4 JSON Parsing with jq

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

3.5 YAML Parsing with yq

yq '.metadata.name' deployment.yaml
yq -i '.spec.replicas = 5' deployment.yaml

---

4. SSH and Remote Access

4.1 SSH Key Generation

ssh-keygen -t ed25519 -C "your_email@example.com"

4.2 SSH Tunneling

ssh -L 8080:localhost:80 user@server
ssh -L 6443:kubernetes-api:6443 user@bastion

4.3 Bastion Host Usage

ssh -J bastion user@internal-server

4.4 rsync

rsync -avzP ./local/ user@remote:/path/

---

5. Performance Monitoring and Troubleshooting

5.1 top and htop

top -b -n 1 | head -20

5.2 vmstat and iostat

vmstat 1 5
iostat -dx 1 5

5.3 free and df

free -h
df -h

5.4 kubectl top

kubectl top nodes
kubectl top pods --sort-by=memory

---

6. Storage Management Basics

6.1 lsblk

lsblk -f

6.2 LVM

sudo pvcreate /dev/nvme1n1
sudo vgcreate data_vg /dev/nvme1n1
sudo lvcreate -l 100%FREE -n data_lv data_vg

6.3 Kubernetes PV/PVC

apiVersion: v1
kind: PersistentVolume
metadata:
  name: local-pv
spec:
  capacity:
    storage: 100Gi
  accessModes: [ReadWriteOnce]
  storageClassName: local-storage
  local:
    path: /mnt/disks/vol1

---

7. curl and API Calls

7.1 HTTP Methods

curl -X POST -H "Content-Type: application/json" -d '{"name":"John"}' https://api.example.com/users

7.2 Kubernetes API Calls

TOKEN=$(cat /var/run/secrets/kubernetes.io/serviceaccount/token)
curl -s --cacert $CACERT -H "Authorization: Bearer $TOKEN" \
  "https://kubernetes.default.svc/api/v1/namespaces/default/pods"

7.3 Useful curl Options

curl -s -o /dev/null -w "%{http_code}" https://api.example.com/health

---

8. Practical One-Liners Collection

8.1 Kubernetes Operations

kubectl get pods -A | awk '$4 != "Running" && NR>1 {print $1, $2, $4}'
kubectl get pods -A -o json | jq -r '.items[] | select(.status.containerStatuses[]?.restartCount > 5) | .metadata.name'

8.2 Log Analysis

kubectl logs deploy/app --since=1h | grep -i error

8.3 Network Debugging

nslookup kubernetes.default.svc.cluster.local
nc -zv service-name 80

---

Conclusion

1. Environment Variables: Base para K8s ConfigMap/Secret
2. Shell Scripting: Esencial para init containers y health checks
3. Text Processing: Fundamental para analizar la salida de kubectl
4. SSH: Importante para depurar nodos
5. Performance Monitoring: Base del troubleshooting

---

Previous: Linux Basics | Next: Container Basics