The reason is we have the ab command as part of the ENTRYPOINT definition.Īnd the URL you pass in the run command will be appended to the ENTRYPOINT script. If you want to pass the URL argument to ENTRYPOINT, you need to pass the URL alone. It will override the whole CMD specified in the Dockerfile.
While running the container, just add the full ab command at the end of the docker run command. Lets look at the difference between CMD and ENTRYPOINT by passing ab commands during docker run. FROM centos:7ĮNTRYPOINT Difference Between ENTRYPOINT and CMD
Using ENTRYPOINT: The executable and argument are separated by commas in the same square bracket. Using CMD: The ab executable and HTTP URL arguments are added in separate square brackets. Hardcode the HTTP endpoint argument as shown in the below examples. We have two ways to get around this problem. The reason is, ab command requires an http endpoint as an argument to start the service. n requests Number of requests to perform Now if you run the container from the above Dockerfile images, it will throw the following error. Let’s take an example of the following Dockerfile. It installs http-tools and starts the ab ( apache benchmark) utility using CMD and Entrypoint. Executing Commands Using ENTRYPOINT and CMD Lets understand these concepts practically. The resulting command will be executed when the container is started. If both ENTRYPOINT and CMD are specified in a Dockerfile, the command specified in CMD will be appended to the ENTRYPOINT command. The default ENTRYPOINT command is /bin/sh -cĬMD, on the other hand, is used to specify the default command and arguments that should be executed when a container is started. In a Dockerfile, ENTRYPOINT and CMD are two different instructions that are used to define how a container should run.ĮNTRYPOINT is used to specify the main command that should be executed when a container is started using the image. In this blog we will look at the key differences between Docker ENTRYPOINT vs CMD instruction using a practical example.
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