Building and managing Docker images

We built some Docker images in the previous section, so by now, you should have some idea about how to write Dockerfiles and create Docker images from them. We've also covered a few best practices regarding it, which, in summary, are as follows:

• Always add the layers that do not change frequently first, followed by the layers that may change often. For example, install your packages and dependencies first and copy the source code later. Docker builds the Dockerfile from the part that you change until the end, so if you change a line that comes at a later stage, Docker takes all the existing layers from the cache. Adding more frequently changing parts later in the build helps reduce the build time and will result in a faster CI/CD experience.
• Combine multiple commands to create as few layers as possible. Avoid multiple consecutive RUN directives. Instead, try to combine them into a single RUN directive by using the && clauses...