Dockerfile

A Dockerfile is a script that contains a series of instructions that are used to build a [[Docker]] image.

Dockerfiles typically include the following information:

The base or parent image we use to create the new image
Commands to update the base OS and install other software
Build artifacts to include, such as a developed application
Services to expose, such a storage and network configuration
Command to run when the container is launched

Here's an example of a Dockerfile to build a .NET application:

# Use the .NET 6 runtime as a base image
FROM mcr.microsoft.com/dotnet/runtime:6.0

# Set the working directory to /app
WORKDIR /app

# Copy the contents of the published app to the container's /app directory
COPY bin/Release/net6.0/publish/ .

# Expose port 80 to the outside world
EXPOSE 80

# Set the command to run when the container starts
CMD ["dotnet", "MyApp.dll"]

In particular:

FROM mcr.microsoft.com/dotnet/runtime:6.0: this command sets the base image to the .NET 6 runtime, which is needed to run .NET 6 apps.

WORKDIR /app: it sets the working directory of the container structure to /app. This is where app files will be copied.

COPY bin/Release/net6.0/publish/ .: this command copies the content within the bin/Release/net6.0/publish folder to the current directory (., which is now set to /app).

EXPOSE 80: it opens the port 80 to the external world. When you run a container using this image, you have to ensure that you are accessing this internal port.

CMD ["dotnet", "MyApp.dll"]: this is the command to run when the container starts. In this case, we are running the dotnet command with the name of the app's [[DLL]].

Backlinks

ACR Tasks

- **Trigger on source code update**: you can configure to build the image every time new code is committed, or a pull request is made or updated, by using `az acr task create`, specifying the Git repo, the branch and the [[docker-file]].