# Create a Docker File and using Docker file Build Images

## Create a Dockerfile and Build Images

A Dockerfile is a text file that contains all the commands a user could call on the command line to assemble an image. This Dockerfile example sets up a lightweight Python application container. It performs several key actions:

* Uses the `python:3.9-slim` image as a base.
* Sets the working directory inside the container to `/app`.
* Copies the current directory's contents into the container at `/app`.
* Makes port 80 available to the container's external network.
* Specifies that the container runs `app.py` with Python when it launches.

### Performing Tasks with Docker in a New Folder

To streamline your Docker workflows, follow these steps to create a folder where you can perform all related tasks:

1. **Create a New Folder:** Open your terminal and use the command `mkdir your-folder-name` to create a new folder where you will carry out your Docker tasks.
2. **Navigate to Your New Folder:** Change your current directory to the newly created folder by entering `cd your-folder-name`.
3. **Initialize Your Docker Project:** Inside the folder, you can now perform all Docker-related tasks, such as initializing Docker projects, creating Docker files, and managing Docker containers and images.

### Create a separate folder

By organizing your Docker tasks within a specific folder, you maintain a clean and efficient workflow.

Use the **mkdir** command to create a directory.

```
mkdir docker_config
```

Navigate to the created directory.

```
cd docker_config 
```

Use the **touch** command to create a file.

```
touch Dockerfile
```

### Create a docker file

Now use the **vi editor** to edit the file.

```
vi Dockerfile
```

```
# Use a base image from Docker Hub
FROM alpine:latest

# Set the working directory in the container
WORKDIR /app

# Copy files from the host machine to the container
COPY . /app

# Install necessary dependencies
RUN apk add --no-cache python3

# Expose a port
EXPOSE 80

# Define a default command to run when the container starts
CMD ["python3", "app.py"]
```

Grant user access

```
chown $USER /var/run/docker.sock
```

### Build an image using the docker file

This Dockerfile provides a clear, reproducible method for building a containerized Python application.

```
docker build -t my-image .
```

This command will build your Docker container based on the instructions in the Docker file you created. Make sure you run this command within the **docker\_config** directory where your Dockerfile is located. The **-t** flag tags your image **my-image** for easy reference.

To verify that your Docker image has been successfully built, use the **docker images** command, which will list all Docker images on your system, including your newly created **my\_image** image. This allows you to confirm that your image is ready for use.

```
docker images
```

<figure><img src="https://1876135298-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FEC5NwtFshv6EATOemuUn%2Fuploads%2FSQZIhF8R2D7g5SwyJXYI%2Fimage.png?alt=media&#x26;token=27f59196-9f46-4ea7-ac3a-5b536e9dd539" alt=""><figcaption></figcaption></figure>

### Manage Images Commands <a href="#h-manage-images-commands" id="h-manage-images-commands"></a>

To remove the images&#x20;

```
docker rmi image_name/imgae_id
```

Lists images

```
docker image ls
```

Tags an image

```
docker tag image_name/image_id  tag_name
```

More commands->

<figure><img src="https://1876135298-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FEC5NwtFshv6EATOemuUn%2Fuploads%2FMP88mAmV1F1u17c1wgQ1%2Fimage.png?alt=media&#x26;token=66956cae-6ec2-49b6-814f-8c32f962041a" alt=""><figcaption></figcaption></figure>

Common Dockerfile Instructions

**FROM**:- Specifies the base image for the Docker image

**RUN**:- Executes a command during the build process

**COPY**:- Copies files from the build context to the Docker image.

**ENV**:- Sets an environment variable in the Docker image

**EXPOSE**:- Exposes a port in the Docker image.

**CMD**:- Specifies the default command to run when the Docker container is started.

**WORKDIR**:- Sets the working directory in the docker image.

**VOLUME**:- Creates a volume in the Docker image.

**USER**:- Sets the user and group ID for the Docker image.

**ENTRYPOINT**:- Specifies the entry point for the Docker container.


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