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Exam AZ-300 topic 3 question 4 discussion

Actual exam question from Microsoft's AZ-300

Question #: 4
Topic #: 3

DRAG DROP -
You plan to create a Docker image that runs an ASP.NET Core application named ContosoApp. You have a setup script named setupScript.ps1 and a series of application files including ContosoApp.dll.
You need to create a Dockerfile document that meets the following requirements:
✑ Call setupScript.ps1 when the container is built.
✑ Run ContosoApp.dll when the container starts.
The Dockerfile document must be created in the same folder where ContosoApp.dll and setupScript.ps1 are stored.
Which four commands should you use to develop the solution? To answer, move the appropriate commands from the list of commands to the answer area and arrange them in the correct order.
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Suggested Answer:

by FailureIsnotAnOption at Jan. 30, 2020, 4:29 p.m.

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Jt909

Highly Voted 5 years, 3 months ago

The only source I've found from MS: https://docs.microsoft.com/en-us/aspnet/core/host-and-deploy/docker/building-net-docker-images?view=aspnetcore-3.1 For what i recall there are subtle differences between CMD and ENTRYPOINT, but I'll choice RUN/CMD because RUN it's used to setup and executes things. This was also useful https://goinbigdata.com/docker-run-vs-cmd-vs-entrypoint/

upvoted 11 times

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[Removed]

Most Recent 4 years, 11 months ago

I would say the last suggested step in the provided answer is correct - that is NOT to use ENTRYPOINT, although I wouldn't use it like this myself. I guess the reason why the suggested answer is correct is because of the explenation given here: https://phoenixnap.com/kb/docker-cmd-vs-entrypoint#:~:text=CMD%20is%20an%20instruction%20that,container%20with%20a%20specific%20executable. "Combine ENTRYPOINT with CMD if you need a container with a specified executable and a default parameter that can be modified easily" - and that's not what we want here. So I'd say RUN and CMD as the last step is correct.

upvoted 4 times

cloudcuckooland

4 years, 9 months ago

i'd agree with this >> running CMD["dotnet","ContosoApp.dll"] is equal to running >dotnet ContosoApp.dll which is valid and required as per the question being asked

upvoted 1 times

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Prash85

4 years, 12 months ago

Consider Entrypoint as the last step.

upvoted 3 times

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thirstylion

5 years ago

The last instruction should be ENTRYPOINT[ ], https://code.visualstudio.com/docs/containers/quickstart-aspnet-core. So the last step should be CMD/ENTRYPOINT

upvoted 3 times

ct84

4 years, 9 months ago

yup, fully agree

upvoted 2 times

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ShadowGum

5 years ago

The answer is correct. To clarify the last step, the question states "when container is built" hence RUN/ENTRYPOINT is correct

upvoted 1 times

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PatMan

5 years ago

Very easy: "RUN actually runs a command and commits the result; CMD does not execute anything at build time, but specifies the intended command for the image" The command does not need to run at build time. Hence, it as to be CMD with ENTRYPOINT

upvoted 3 times

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cdrx

5 years ago

There is nothing in the question that states the application layout, so why should we set the workdir in the docker file ? Is this related to the dotnet way of scalfolding the apps ?

upvoted 1 times

macco455

4 years, 10 months ago

Aren't we doing this to appease: The Dockerfile document must be created in the same folder where ContosoApp.dll and setupScript.ps1 are stored. ??

upvoted 1 times

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PT1

5 years, 1 month ago

Question says "✑ Call setupScript.ps1 when the container is built." ---> This is possible with 'RUN' instruction, not with 'CMD'. This is the reason last box is what it is.

upvoted 3 times

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FailureIsnotAnOption

5 years, 4 months ago

https://docs.microsoft.com/en-us/azure/app-service/containers/tutorial-custom-docker-image

upvoted 1 times

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FailureIsnotAnOption

5 years, 4 months ago

I'm no expert at this, for sure. But when I look up references to this that include "dotnet" AND "contosoapp.dll" it seems that the last choice should be the CMD/Entrypoint option. Please advise.

upvoted 1 times

cloudcuckooland

4 years, 9 months ago

if the last choice was cmd/entrypoint, this would mean that when the container is run, the CMD would be passed to the entry point as a parameter. when cmd and entrypoint are used together this is how they interact. The question does not ask for powershell to be passed to the dll at startup. The given answer is correct, the RUN command will execute once at build and the CMD command is the default command when the container starts.

upvoted 5 times

tartar

4 years, 9 months ago

The given answer is correct

upvoted 1 times

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