Reading Dockerfiles and running containers

Containerization and Virtualization Concepts

Julia Ostheimer

Freelance AI Consultant

Recap of Docker terms

From Dockerfile to Docker container

Docker instructions vs. Docker commands

Docker instructions detail how to build a Docker image

Docker instructions in Dockerfile

Docker commands: Commands via Command Line Interface (CLI)

Docker commands in CLI

Format of a Dockerfile

Dockerfile - Comment

Format of a Dockerfile

Dockerfile - Instruction

Format of a Dockerfile

Dockerfile - Command of Docker instruction

Format of a Dockerfile

Dockerfile - Argument of Docker instruction

Sequential order in Dockerfiles

Execution in sequential order
Start of a Dockerfile:
- Metadata
- Comments
- Arguments
- FROM instruction

Overview of Docker instructions

Important Docker instructions
- FROM
- COPY
- RUN
- ENTRYPOINT

FROM instruction

Specifies an existing Docker image
Defines the image we are building on
- "Starting point"

Syntax:

FROM <name_of_image>

Example:

# Define the image on which to build
FROM python:3.10

COPY instruction

Copies files or directories
- From source (<source>) to destination (<destination>)
- Files that are needed in following Docker instructions

Syntax:

COPY <source> <destination>

Example:

# Copy files/folders to the main folder of the container
COPY . .

RUN instruction

Runs a command within a container
- Can be any command that could be run in a CLI

Syntax:

RUN <command>

Example:

# Install the application's dependencies
RUN pip install -r requirements.txt

ENTRYPOINT instruction

Defines the container's default behavior
- Specifies command to run at initiation
- The primary purpose of the container

Syntax:

ENTRYPOINT ["command", "argument"]

Example:

# Run the script when the container starts
ENTRYPOINT ["python", "hello_world.py"]

Assembling instructions to Dockerfile

# Define the image on which to build
FROM python:3.10

Assembling instructions to Dockerfile

# Define the image on which to build
FROM python:3.10

# Copy files/folders to the main folder of the container
COPY . .

Assembling instructions to Dockerfile

# Define the image on which to build
FROM python:3.10

# Copy files/folders to the main folder of the container
COPY . .

# Install the application's dependencies
RUN pip install -r requirements.txt

Assembling instructions to Dockerfile

# Define the image on which to build
FROM python:3.10

# Copy files/folders to the main folder of the container
COPY . .

# Install the application's dependencies
RUN pip install -r requirements.txt

# Run the script when the container starts
ENTRYPOINT ["python", "hello_world.py"]

Docker build command

Builds Docker image from a Dockerfile
- Dockerfile needs to be located in build's context (<context>)
- Executed as command with Docker client via CLI

Syntax:

docker build <context>

Docker run command

Creates and runs Docker container from Docker image
- Docker image needs to be specified as argument (<name_of_image>)
- Executed as command with Docker client via CLI

Syntax:

docker run <name_of_image>

Let's practice!

Containerization and Virtualization Concepts