lipikam/quick-docker

quick-docker

A quick overview about docker for developers.

Docker is one implementation of container based virtualization technologies.

Pre-Virtulaization Issues:

• Cost
• Slow deployment
• Hard to migrate

Hypervisor based virtualization:

Benefits:

• Cost effective
• Easy to scale

Limitation:

• Kernel resource duplication
• Application portability issue

Container based virtulization:

Benefits:

• cost effective
• fast deployment
• Application portability

Difference : In hypervisor based system OS/Kernel duplication and virtulization at hardware level whereas container based system shares same kernel/OS which is container engine and the virtulization happens at the OS level. Hence more efficient and light weighted.

Why to run the applications in different containers not in one VM ?

• runtime isolations (In case application A requires JRE7 and application B requires JRE8)

Registries and Repositories:

• Images are stored under registries
• You can host your own registry or use docker's existing public registry which is called DockerHub.
• Inside the registry, images are stored under repositories.
• Docker repository is a collection of different docker images with the same name, that have different tags, each tag usually represents a different version of the image.

Why using official docker images:

• Proper documentation
• Dedicated team for image content review
• Timely security update