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Lab 5.1 suggested corrections

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While this was handled in another discussion ("Lab 5.1"), I would like to suggest that you add that some of the commands in Lab 5.1 are an example only and should not actually be executed as part of the Lab. This includes:

student@ubuntu:~$ sudo docker image pull myregistry.com:5000/alpine:latest

and

student@ubuntu:~$ sudo docker image push myregistry.com:5000/alpine:training

and, finally,

student@ubuntu:~$ sudo docker image rm -f alpine:latest nginx:latest

You might want to separate the example "alpine:latest" from the real "nginx:latest" since the later will really work as part of the Lab. However, because it does work, you should switch the order of the image removal with the last command (inspect) in the Lab:

student@ubuntu:~$ sudo docker image inspect nginx

as inspecting the just removed nginx:latest image will fail. By switching the order of the commands (inspect followed by rm), the Lab will work as expected.

Thanks!

Comments

  • chrispokorni
    chrispokorni Posts: 2,208
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    Thank you for your detailed feedback, Kevin!
    I will revise the exercise and make the necessary corrections to improve readability and flow.

    Regards,
    -Chris

  • Jenad1kr
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    @chrispokorni , when I execute the command, sudo docker image pull myregistry.com:5000/alpine:latest
    i get
    Error response from daemon: Get https://myregistry.com:5000/v2/: net/http: request canceled wh
    ile waiting for connection (Client.Timeout exceeded while awaiting headers)

    Do I need to open a firewall port or something?
    thx.

  • chrispokorni
    chrispokorni Posts: 2,208
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    Hi @Jenad1kr,

    That command is used for illustration purposes only. Typically where you see domains similar toexample.com, myexample.com, or myresource.com these domains are not real, unless they are registered by you :wink:

    Regards,
    -Chris

  • go2vijay
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    @Chris,it still fails .can you suggest.

    Digest: sha256:c628b67d21744fce822d22fdcc0389f6bd763daac23a6b77147d0712ea7102d0
    Status: Image is up to date for nginx:latest
    docker.io/library/nginx:latest
    vijaykumar_palaniswamy@ubuntu:~$ sudo docker image pull myregistry.com:5000/alphine:training
    Error response from daemon: Get https://myregistry.com:5000/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)

  • toastboy
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    Adding my 2 cents here: if a step is expected to fail in a teaching lab such as this without the students taking steps which are themselves more complicated than what's being taught in the course (in this case, hosting their own secure private registry) then it really ought to be identified as such. "For example, if you had access to a private registry called 'myregistry.com'"

  • chrispokorni
    chrispokorni Posts: 2,208
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    Hi @go2vijay,

    In an earlier comment you may find the reason it still fails:

    That command is used for illustration purposes only. Typically where you see domains similar to example.com, myexample.com, or myresource.com these domains are not real, unless they are registered by you :wink:

    @toastboy, a clarifying note will be added in a future course update release.

    Regards,
    -Chris

  • rogerh
    rogerh Posts: 10
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    Hi @chrispokorni

    I had the same problem. Thanks for the clarification. Understanding the syntax makes sense. A question then has to do with the use of Dockerhub. I have an account so I tried the following syntax:

    $ sudo docker image pull hub.docker.com/opaekaa/my_ubuntu:my-ubuntu

    I thought it would pull the container my_ubuntu to my local repository with my-ubuntu. I instead got what looks like the binary.

    So I tried the following syntax:

    $ sudo docker pull opaekaa/my_ubuntu:latest

    Error response from daemon: manifest for opaekaa/my_ubuntu:latest not found: manifest unknown: manifest unknown

    It is apparent I don't understand the syntax after all.

  • chrispokorni
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    Hi @rogerh,

    The command $ sudo docker pull opaekaa/my_ubuntu:latest assumes that the image exists in your repository on Docker Hub, and it will attempt to pull it into the local image cache of the Docker Host.

    Regards,
    -Chris

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