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Docker Containers

Containers are the fundamental building blocks of Docker applications. In WhaleTUI, you can manage containers efficiently through an intuitive interface that simplifies common operations.

What are Containers?​

Docker containers are lightweight, standalone, and executable packages that include everything needed to run an application: code, runtime, system tools, system libraries, and settings.

Container Lifecycle in WhaleTUI​

1. Viewing Containers​

The Containers tab in WhaleTUI displays all containers on your system:

  • Running Containers: Currently active containers
  • Stopped Containers: Containers that have been stopped
  • Container Status: Health, uptime, and resource usage

2. Container Information​

Each container displays key information:

  • Name: Human-readable container identifier
  • Image: Base image used to create the container
  • Status: Current state (running, stopped, paused)
  • Ports: Exposed ports and mappings
  • Size: Disk space used by the container

Basic Container Operations​

Starting a Container​

# Using WhaleTUI UI
1. Press ':' then type 'containers' to navigate to Containers view
2. Select a stopped container using arrow keys
3. Press 's' to start the container
4. Container will begin running

# Using Docker CLI (alternative)
docker start <container_id>

Stopping a Container​

# Using WhaleTUI UI
1. Select a running container using arrow keys
2. Press 'S' to stop the container
3. Container will stop gracefully

# Using Docker CLI (alternative)
docker stop <container_id>

Restarting a Container​

# Using WhaleTUI UI
1. Select a container (running or stopped) using arrow keys
2. Press 'r' to restart the container
3. Container will restart with the same configuration

# Using Docker CLI (alternative)
docker restart <container_id>

Removing a Container​

# Using WhaleTUI UI

1. Select a stopped container using arrow keys
2. Press 'd' to delete the container
3. Confirm the action with 'Enter'
4. Container will be permanently removed

# Using Docker CLI (alternative)
docker rm <container_id>

Advanced Container Operations​

Viewing Container Logs​

# Using WhaleTUI UI
1. Select a container using arrow keys
2. Press 'l' to open logs view
3. Navigate through log entries using arrow keys
4. Press 'ESC' to return to main view

# Using Docker CLI (alternative)
docker logs <container_id>

Inspecting Containers​

# Using WhaleTUI UI
1. Select a container using arrow keys
2. Press 'i' to inspect the container
3. View detailed information in JSON format
4. Press 'ESC' to return to main view

# Using Docker CLI (alternative)
docker inspect <container_id>

Container Configuration​

Environment Variables​

Containers can be configured with environment variables:

# Set environment variables when running
docker run -e VAR_NAME=value -e ANOTHER_VAR=value image_name

# Environment variables can be configured when creating containers

Port Mappings​

Expose container ports to the host:

# Map host port 8080 to container port 80
docker run -p 8080:80 nginx

# Port mappings can be configured when creating containers

Volume Mounts​

Persist data between container runs:

# Mount host directory to container
docker run -v /host/path:/container/path image_name

# Volume mounts can be configured when creating containers

Container Resource Management​

Resource Limits​

Set limits on container resource usage:

# Limit memory and CPU
docker run --memory=512m --cpus=1.0 image_name

# Resource limits can be configured when creating containers

Resource Monitoring​

WhaleTUI provides real-time resource monitoring:

  • CPU Usage: Current CPU consumption
  • Memory Usage: RAM usage and limits
  • Network I/O: Network traffic statistics
  • Disk I/O: Storage access patterns

Best Practices​

Container Naming​

Use descriptive names for containers:

# Good naming examples
web-server-prod
database-staging
api-gateway-dev

# Avoid generic names
container1
test
temp

Resource Cleanup​

Regularly clean up unused containers:

# Remove stopped containers
docker container prune

# Use Docker CLI to clean up stopped containers

Health Checks​

Implement health checks for production containers:

# Add health check to Dockerfile
HEALTHCHECK --interval=30s --timeout=3s \
  CMD curl -f http://localhost/ || exit 1

Troubleshooting​

Common Issues​

Container Won't Start​

# Check container logs
docker logs <container_id>

# Verify image exists
docker images

# Check resource availability
docker system df

Container Performance Issues​

# Monitor resource usage
docker stats <container_id>

# Check for resource limits
docker inspect <container_id> | grep -i memory

Network Connectivity​

# Test container networking
docker exec <container_id> ping google.com

# Check port bindings
docker port <container_id>

Next Steps​

Swarm Mode​

When running in swarm mode, containers are distributed across multiple nodes:

# Deploy service across multiple nodes
docker service create --name web --replicas 3 nginx:latest

# Scale service across available nodes
docker service scale web=5

# Check service distribution across nodes
docker service ps web

Key Concepts:

  • Node Distribution: Containers are automatically distributed across available nodes
  • Load Balancing: Swarm provides built-in load balancing for services
  • High Availability: Services continue running even if individual nodes fail
  • Resource Management: Swarm considers node resources when scheduling containers