Introduction to Docker

What is Docker

• Container Platform that separates the application from underlying infrastructure by bundling up code & its dependency into an entity which always runs similarly on all environments.
• Solves problem of inconsistent development environments across different machines especially production
• Often compared to VMs, OS on VMs runs on a virtualised hardware while in case of Docker Guest OS dependency is removed via sharing kernel with host OS.

Docker	VM

The Docker Architecture

• Docker uses a client-server model
  • Server : Docker Daemon (Manages Object (Network/Container/Image/..))
  • Client : Docker CLI

High Level Docker Architecture

Docker Client Interacting with Docker Server (Daemon)

• Containers is not a new concept, Docker just made it popular, Hypescale is the defacto standard
• Docker Popularity
  • Market Demand
  • Well Established Technology

Docker utilises several features of Linux Kernel Namespaces to provide functionality. Docker supports several features :

Namespaces

• The pid namespace: Process Isolation (PID: Process ID)
• The net namespace: Managing Network Interfaces (NET: Networking)
• The ipc namespace: Managing access to IPC resources (IPC: Interprocess Communication, SysV)
• The mnt namespace: Managing filesystem mount points (MNT: Mount)
• The uts namespace: Isolating Kernel and version Identifiers. (UTS: Unix Timesharing System)

Control Groups

• Resource Limiting
• Prioritization : some groups are given larger share of cpu or i/o utilisation
• Accounting : measures a group’s usage
• Control : Freezing grps of process

UnionFS

• Merging : overlay filesystem branches to merge changes
• Read/Write: branches can be read-only or read-write

Installing Docker

Follow this guide : https://docs.docker.com/desktop/

Make sure to start docker daemon before trying out all commands

Check if docker installed correctly : docker run hello-world

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