Container Issues

Container Issues

Debug Docker and Kubernetes container problems.

Docker Debugging

Container Not Starting

# View logs
docker logs container_name
docker logs --tail 100 container_name

# Inspect container
docker inspect container_name

# Check exit code
docker inspect container_name --format='{{.State.ExitCode}}'

# See last run
docker ps -a

Container Crashes

# Follow logs
docker logs -f container_name

# Events
docker events

# Stats
docker stats container_name

# Exec into running container
docker exec -it container_name /bin/sh

Network Issues

# Inspect networks
docker network ls
docker network inspect bridge

# Container networking
docker inspect container_name | grep -A 20 NetworkSettings

# Test from inside container
docker exec container_name ping other_container
docker exec container_name curl http://service:8080

Resource Issues

# Container resource usage
docker stats

# Check limits
docker inspect container_name | grep -A 10 HostConfig

# View system resources
docker system df

Kubernetes Debugging

Pod Not Starting

# Pod status
kubectl get pods
kubectl describe pod pod_name

# Events
kubectl get events --sort-by=.lastTimestamp

# Logs
kubectl logs pod_name
kubectl logs pod_name --previous  # Previous instance

Common Pod States

Debug Commands

# Exec into pod
kubectl exec -it pod_name -- /bin/sh

# Copy files
kubectl cp pod_name:/path/file ./file

# Port forward
kubectl port-forward pod_name 8080:80

# Run debug container
kubectl run debug --rm -it --image=busybox -- /bin/sh

Network Debugging

# Test connectivity
kubectl exec pod_name -- ping service_name
kubectl exec pod_name -- curl http://service:port

# DNS
kubectl exec pod_name -- nslookup kubernetes

# Service endpoints
kubectl get endpoints service_name

Resource Issues

# Resource usage
kubectl top pods
kubectl top nodes

# Describe for resource limits
kubectl describe pod pod_name | grep -A 5 Limits

# Check resource quotas
kubectl describe resourcequota

Image Issues

# Check image
docker images | grep myimage

# Pull manually
docker pull myimage:tag

# Inspect image
docker image inspect myimage:tag

# Build with no cache
docker build --no-cache -t myimage .

Volume/Storage Issues

Docker

# List volumes
docker volume ls

# Inspect volume
docker volume inspect volume_name

# Check mounts
docker inspect container_name | grep -A 10 Mounts

Kubernetes

# PVC status
kubectl get pvc

# Describe PVC
kubectl describe pvc pvc_name

# Check storage class
kubectl get storageclass

Quick Fixes

# Docker: Restart container
docker restart container_name

# Docker: Recreate container
docker-compose up -d --force-recreate service

# K8s: Delete pod (will recreate)
kubectl delete pod pod_name

# K8s: Rollout restart
kubectl rollout restart deployment/app