Reading Dockerfiles and running containers

Concetti di containerizzazione e virtualizzazione

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!

Concetti di containerizzazione e virtualizzazione