Debugging Running Containers — docker exec, logs, inspect

# Running containers
docker ps

# Including stopped containers
docker ps -a

# Real-time resource usage monitoring
docker stats

# A specific container only
docker stats my_app

# Full logs
docker logs my_app

# Last 100 lines
docker logs --tail 100 my_app

# Follow in real time
docker logs -f my_app

# Include timestamps
docker logs -t my_app

# Logs since a specific time
docker logs --since "2024-01-15T10:00:00" my_app

# Open a shell (use sh if bash is not available)
docker exec -it my_app bash
docker exec -it my_app sh

# Run a single command
docker exec my_app cat /etc/nginx/nginx.conf

# Connect as root (for permission debugging)
docker exec -u root -it my_app bash

# Check environment variables
docker exec my_app env

# Full information (JSON)
docker inspect my_app

# Extract a specific field
docker inspect -f '{{.State.Status}}' my_app
docker inspect -f '{{.NetworkSettings.IPAddress}}' my_app
docker inspect -f '{{range .Mounts}}{{.Source}} -> {{.Destination}}{{"
"}}{{end}}' my_app

# List of environment variables
docker inspect -f '{{range .Config.Env}}{{.}}{{"
"}}{{end}}' my_app

# Check the exit code
docker inspect my_app | grep -A5 '"State"'

# View logs of a crash-looping container
docker logs my_app 2>&1 | tail -50

# Override entrypoint to get a shell
docker run -it --entrypoint sh my_image:latest

# Copy a file from a stopped container
docker cp dead_container:/app/error.log ./error.log

# List container networks
docker network ls

# Network details (which containers are connected)
docker network inspect bridge

# Ping another container from a container (use the container name)
docker exec my_app ping db

# Check DNS resolution
docker exec my_app nslookup db

# Check listening ports
docker exec my_app ss -tlnp

# Check size per layer
docker history my_image:latest

# Detailed layer information
docker history --no-trunc my_image:latest