How can you update an existing Docker image?

Updating an existing Docker image typically involves modifying the image's layers or configuration and then creating a new image based on those modifications. One effective way to achieve this is by using the docker build command. When you run docker build, you can specify a new tag for the modified image, allowing you to maintain different versions of the image.

Additionally, docker pull is used to fetch the latest version of an image from a registry, but it doesn't directly update the local image itself. Instead, it ensures that your local image is synchronized with the upstream repository, potentially replacing an older version with a newer one if it's available. However, this does not involve modifying the existing image.

The other options don't provide a direct way to update an existing image in the context of creating a new version. The docker update command is not used for modifying images; it manages container resources. Using docker commit allows you to create a new image from a modified container state, but it is less preferred for best practices in image management and version control compared to docker build. Therefore, using docker build to create a new image with a new tag is the most accurate method for updating an existing Docker image.