# What is the difference between RUN and CMD in a Dockerfile?

`RUN` and `CMD` are both instructions used in Dockerfiles, but they have different purposes.

## `RUN` instruction

`RUN` is used to execute commands during the build process of a Docker image. These commands are run in a new layer on top of the current image and their result is saved in the new image layer. The commands specified with `RUN` are typically used to install software packages, update system configurations, create directories, and perform other tasks that are necessary to configure the image.

## `CMD` instruction

`CMD`, on the other hand, is used to specify the default command to run when a Docker container is started from the image. This command is only executed when the container is started and it can be overridden by passing a different command to the docker run command line. `CMD` is typically used to start a service or application in the container.

To summarize, `RUN` is used to execute commands during the build process of a Docker image, while `CMD` is used to specify the default command to run when a Docker container is started from the image.

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