What instruction does a Dockerfile usually start with when creating a container?

A Dockerfile usually starts with the FROM instruction, which specifies the base image from which the container will be built. This instruction sets the foundation on which subsequent commands will be executed.

Example:

FROM ubuntu:20.04

This means that the container will be built on the Ubuntu image version 20.04. After FROM, there are usually instructions for installing dependencies, copying files, and configuring the environment.