What is Docker?

Docker is a platform to

run/share/manage

 Containers

Containers

• Are a self contained environment
• Should NOT contain application data
• Should be ephemeral

Containers vs VMs

Images

• Define an environment (container)
• Built in Layers

Images vs Snapshots

• Images are smaller
• Docker has better tools (registry, compose, networking)
• Less to manage

Layers

• Layers are steps in a Dockerfile
• Layers are unique, but can be shared and reused

Build with Layers

• Only layers "above" and change need to be rebuilt
• Dockerfiles can be optimized by changing the order of the build

Containers in Development

• "Builds here but not there"
• "Did you set this ENV variable?"
• "Do you have packageX installed"
• "Does the OS build tag match the Product build tag?"

Having a consistent environment

Traditional Solutions

• Central/Shared Servers maintained by staff
• VM Snapshots
• Managing the "Extra" stuff yourself

Docker Solutions

Docker Images

• Split environment and source code
• Base images as boilerplate for new processes
• Docker compose for networking containers (database to a web framework)