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Chapter 12 Lab included in study material ???

douglukas
douglukas Posts: 11
in LFS201 Class Forum - Discontinued

I've experienced a couple times where the Lab Exercise sent us astray from the actual material being studied. I figure this is intentional forcing the student to venture out into man/info/help pages to seek the answer. That's great and it's very helpful.

BUT, in chapter 12 Lab Exercise we're asked to perform actions using the dd command (never mentioned at all) and then perform a couple tasks that circle back to using the "kill command" and "jobs" command.

Is there a relevance that I'm missing to this exercise?
Did I just flat-out miss the boat in the study material somewhere?
Is this what the actual test labs will do during the certification process?

I was able to get through it although the outputs did not work as described in the solution. That's causing me to go outside the course to learn the Linux "dd" command in detail so I can better understand its usage and hopefully draw some relevance to chapter 12.

Just wondering if anyone who's already passed this portion can shed some learning light on this.

Any and all help will be greatly appreciated.

Doug

Comments

  • luisviveropena
    luisviveropena Posts: 1,343

    Hi @douglukas

    BUT, in chapter 12 Lab Exercise we're asked to perform actions using the dd command
    (never mentioned at all) and then perform a couple tasks that circle back to using the "kill command" and "jobs" command.

    >

    Is there a relevance that I'm missing to this exercise?

    Of course it's relevant, because Chapter 12 is about Process Monitoring; we are using "dd" in this lab to read from one place (/dev/urandom) and write to another place (/dev/null). So that process should continue until you kill it. We also are asked to change the state of the process.

    Perhaps what made you confused was that you didn't know the "dd" command, so you lost the picture. But this is a very well known tool and it's pretty good you are learning how to use it. In the linux and open source world learning some things by ourself is part of the culture, so even if we try to provide the most of things we can, there are also some other stuff you need to investigate by yourself, because that will happen soon or later.

    If anything is not working for you, feel fee to ask. For that, please provide your distro name and version, kernel version, the command you are running and the error you are getting.

    Many regards,
    Luis.

  • douglukas
    douglukas Posts: 11

    What wasn't working according to the solutions was the
    $ fg
    $ ^Z
    $ ps -C dd -o pid,cmd,stat

    After the $fg command it moves to a blinking running process cursor, so I'm unclear on how/when to invoke the $^Z command.

    Without any previous direction on this action, I'm left to just experiment and try to research it.

    Bottom line is that I've yet to be able to complete the solution as defined no matter what I try.

  • luisviveropena
    luisviveropena Posts: 1,343

    You are trying without the dollar symbol, right?

    If possible, provide a screenshot with the commands and the outputs, starting from item 1 (dd if=/dev/urandom of=/dev/null &).

    Please also provide the distro you are working with and version.

    Regards,
    Luis.

  • douglukas
    douglukas Posts: 11

    Ubuntu 18.04

    Tried it a couple different ways but each time after the "fg" and "^Z" commands I had to Ctl-C to exit out of it. Images attached of my path and outputs.
    Thanks,


  • coop
    coop Posts: 917

    I"m not sure what the problem is. You should not be hitting Ctl-C before doing th eps command. The steps in the solution work perfectly for me. The whole point is that CTL-Z suspends the process but it still shows up with ps. After you do a fg and then CTL- C it is gone. So something is missing in how you are seeing this. As best I can see the material in the lab and the solution works perfectly. Please let me know if I am begin blind about something ;)

    On the question of dd, as Luis says, it is a very basic tool used every day, such as ls, or cp, cat, echo etc, and it is covered in LFS101x which is a prerequisite of this course, or anything equivalent. We also don't teach in LFS201 other basic tools like vi, nano, gedit, emacs, etc.

  • douglukas
    douglukas Posts: 11
    edited July 2020

    So after initiating the fg command does the process take time or should it be quick. I'm waiting about 30 seconds before I give up. Should I be waiting longer to finish the command?

  • douglukas
    douglukas Posts: 11
    edited July 2020

    I got it now! So in the solution from the lab the 2nd line (see image below) shows what I thought was a ^Z (shift-6 symbol). NO, dumb me didn't realize that you're are to invoke a CTL-Z after initiating the fg command.

    The CTL-Z gets you out of the fg command. Problem with the Lab info is that when they placed the $ ^Z, you get the impression that the fg command initiates and completes. It does not. That's why you have to type CTL-Z after invoking "fg" command (see below)

    NOTE: in the image above, there is no $ in front of the CTL-Z (^Z). I was actually trying to type the CARAT symbol (Shift-6) after the fg command. Also note that there is an output of [1]+ Stopped ...... that follows my CTL-Z input. This isn't shown in the solution above. Perhaps my Ubuntu 18.04 distro has something to do with this.

    All good now that my brain dead moment and a bit of confusing lab text is over.

  • luisviveropena
    luisviveropena Posts: 1,343

    Hi @douglukas ,

    Many things can be confused when they are unknown to us. I don't think the lab is confusing itself, perhaps it was a bit difficult to understand it. I'm glad that you were able to get it.

    Regards,
    Luis.

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