Booting Sandbox Part II

1. I want to understand what initramfs is and it's role in booting.
2. I will to deliberately miscofigure initramfs to see it's effects.
3. I will then reconfigure the system so that it is returned to normal operation.

1. As is always the case, since I didn't request a lesson with my lab, I don't get one. There is no context or guide stage in the lab. Just a few obscure reference to file-paths. I have Shevek make me a lesson plan so I have a shot at learning in this sandbox.

   What Did You Hand Me, Shevek?

   

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   initramfs Lab 1

   

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   initramfs Lab 2

   

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   initramfs Lab 3

   

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   initramfs Lab 4

   

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   initramfs Lab 5

   

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   initramfs Lab 6

   

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   initramfs Lab 7

   

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   initramfs Lab 8

   

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   initramfs Lab 9

   

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2. In order to do the lab, I need to damage or remove the initramfs image, per what Shevek states. Unfortunately at no point in time does he make it apparent how I am supposed to do this. I consult with Shevek. Shevek, how do we destroy my virtual machine? He provides me three options for doing so.

   Damaging initramfs 1

   

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   Damaging initramfs 2

   

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   Damaging initramfs 3

   

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   Damaging initramfs 4

   

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   Damaging initramfs 5

   

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   Damaging initramfs 6

   

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3. I proceed to set up the conditions for the fault. I follow Sheveks instructions to the detail. But, yet again, I encounter a limitation to the lab. Despite having followed instructions and simply changed the name of initramfs, I am not yielding an emergency shell. The screen sits idly. I attempted a force restart to no avail. Shevek goes on to explain we created an even more catastrophic failure than just initramfs. The Kernel can not even start the initramfs environment. Not to worry, there is a solution.

   Changing the Name of initramfs

   

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   Rebooting 1

   

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   Rebooting 2

   

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   Rebooting 3

   

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   Booting Fault Explained 1

   

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   Booting Fault Explained 2

   

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   Booting Fault Explained 3

   

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   Booting Fault Explained 4

   

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   Booting Fault Explained 5

   

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   Booting Fault Explained 6

   

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4. I follow the steps Shevek lays out for me and it works. When prompted in the GRUB menu to select a Kernel, I select the one whose initramfs has not been corrupted. I'm not certain HOW this gives me access to my directory, but it works. I change the name of initramfs back to it's original state. I reboot, select the original Kernel and it works as it did before.

   Using the "Rescue" Kernel 1

   

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   Using the "Rescue" Kernel 2

   

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   Using the "Rescue" Kernel 3

   

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   Rebooting With the Original Kernel

   

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   Booting Success

   

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5. I feel a little shaky on what a driver is and, seeing as to how they appear to play such a vital role in booting, I ask Shevek to elaborate on what they are. I appear to have the correct general understanding, but as always, Shevek refines it.

   Drivers Explained 1

   

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   Drivers Explained 2

   

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   Drivers Explained 3

   

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   Drivers Explained 4

   

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6. I return to the initramfs lab, prompt Shevek that I have reconfigured my VM to boot correctly, and proceed. I employ the command sudo dracut --omit lvm --force. This creates a new initramfs, leaves out the LVM module, and will cause boot to fail into dracut. I will ask for more clarification on how that command works in the next section.

   Forcing dracut 1

   

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   Forcing dracut 2

   

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   Forcing dracut 3

   

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   Forcing dracut 4

   

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   Forcing dracut 5

   

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   Forcing dracut 6

   

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   Forcing dracut 7

   

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   Forcing dracut 8

   

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7. The command sudo dracut --omit lvm --force leaves a thorn in my side. I am not the type of person to blindly type commands I have no comprehension of. I also know philosophy majors that would struggle to comprehend a man page. I consult Shevek to break down the command, piece by piece.

   Rebuilding initramfs 1

   

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   Rebuilding initramfs 2

   

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   Rebuilding initramfs 3

   

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   Rebuilding initramfs 4

   

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   Rebuilding initramfs 5

   

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8. I return to Sheveks new lab and proceed with his instructions from dracut. However, I encounter yet antoher speed bump. None of the commands I'm required to use work. What's going on here?

   New Lab Process 1

   

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   New Lab Process 2

   

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   New Lab Process 3

   

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   New Lab Process 4

   

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   New Lab Process 5

   

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   New Lab Process 6

   

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   Minor Command Issues

   

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9. Shevek comes up with a way around this, or so I think. He instrcuts me to call commands directly by their PATH. I try and do this, but that doesn't even work. Something is seriously wrong here. Shevek keeps overlooking details. This lab only has experiential and exposure value. Nothing about it is working the way it's supposed to.

   Commands by PATH 1

   

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   Commands by PATH 2

   

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   Commands by PATH 3

   

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   Still Not Working, Shevek

   

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10. Not to worry, Shevek has another solution that sure to at least bring my system back to it's original state AND he has amother method for simulating failure to dracut. I could just use snapshot, but I would like to learn how to recover the system in such a situation. We disabled the LVM. It contains all the commands. How did Shevek not see this coming? Or is he deliberately doing this? I wonder. I follow his lead and boot from CD-ROM.

    System Rescue Via CDROM 1

    

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    System Rescue Via CDROM 2

    

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    System Rescue Via CDROM 3

    

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    System Rescue Via CDROM 4

    

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    System Rescue Via CDROM 5

    

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    System Rescue Via CDROM 6

    

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    System Rescue Via CDROM 7

    

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    System Rescue Via CDROM 8

    

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    System Rescue Via CDROM 9

    

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    System Rescue Via CDROM 10

    

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11. Before I proceed with using chroot in order to reapir initramfs, I would like to better understand what it is exactly it does, and what it is used for. Shevek explains chroot exists for just such a purpose.

    chroot Explained 1

    

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    chroot Explained 2

    

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    chroot Explained 3

    

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    chroot Explained 4

    

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    chroot Explained 5

    

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    chroot Explained 6

    

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12. I attempt Sheveks final lab with tremendous success. dracut loads as required. I am then able to activate LVM manually to access the tools I need. I am then able to mount root, prep chroot, chroot and rebuild initrafms. It took a long time to get here. I still have questions.

    initramfs Recovery 1

    

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    initramfs Recovery 2

    

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    initramfs Recovery 3

    

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    initramfs Recovery 4

    

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    initramfs Recovery 5

    

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    initramfs Recovery 6

    

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    initramfs Recovery 7

    

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    initramfs Recovery 8

    

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    initramfs Recovery 9

    

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    initramfs Recovery 10

    

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    initramfs Recovery 11

    

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    initramfs Recovery 12

    

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    initramfs Recovery 13

    

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    initramfs Recovery 14

    

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    initramfs Recovery 15

    

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13. I'd love to say I know what I just did, but I simply don't understand a lot of it. I consult Shevek regarding what's going on with the mount commands. He explains why they are neccessary before we can employ chroot.

    mount Commands Explained 1

    

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    mount Commands Explained 2

    

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    mount Commands Explained 3

    

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    mount Commands Explained 4

    

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    mount Commands Explained 5

    

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    mount Commands Explained 6

    

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14. As I will be making a habit of doing to make certain I'm actually learning something, I repeat back to Shevek my new found understanding of to the objectives stated at the beginning of the lab. For a change, I am mostly right.

    I still appreciate how Shevek refines what I've learned so it's more comprehensible.

    Objectives Learned 1

    

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    Objectives Learned 2

    

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    Objectives Learned 3

    

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    Objectives Learned 4

    

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    Objectives Learned 5

    

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Corrupting initrafms is no simple task when an LVM is involved. After three tries, Shevek and I managed to get the behavior of dracut we were looking for. Renaming initramfs only resulted in the Kernel being unable to locate initrafms. This resulted in no emergency shell and required the use of a rescue Kernel to salvage the system. Next, we tried muting the LVM at boot. This, however, resulted in having tools that existed somewhere on disc, but were unreachable nonetheless. This much more severe fault required booting from CDROM. Lastly, the effective method employed to get the desired results was modifying GRUB at boot.

Tiny root in RAM
Drivers waiting for first breath
Kernel finds its way

Shevek7