Docker Full Tutorial — Part 2
In Part 1, we understood why Docker exists.
In this part, we will understand the most important concept:
what a container actually is.
Simple Definition of a Container
A container is a lightweight, isolated environment
that runs an application along with everything it needs.
That includes:
- Application code
- Runtime
- Libraries
- Environment variables
What a Container Is NOT
- It is not a full operating system
- It does not include its own kernel
- It is not a virtual machine
Containers share the host machine’s Linux kernel.
This is why they are fast and lightweight.
How Containers Work Internally (Concept Level)
Docker containers use Linux features such as:
- Namespaces – isolation
- cgroups – resource limits
- Filesystem layers – efficiency
You do NOT need to master Linux internals right now.
Just understand this:
Containers feel like separate machines, but they are not.
Container vs Virtual Machine (Clear Comparison)
- VM boots a full OS → slow
- Container starts a process → fast
- VM uses more memory
- Container uses minimal memory
Why Containers Start So Fast
Because:
- No OS boot process
- No hardware emulation
- Direct execution on host kernel
Real-Life Analogy
Think of containers like:
- Different apps on your phone
- Each app is isolated
- But all share the same phone OS
Important Beginner Rule
Do not confuse container isolation with full isolation.
Containers are secure, but they are not magic.
In Part 3, we will understand:
- Docker architecture
- Docker client
- Docker daemon
- Images vs containers
