Today I gave a fresh try to the tandem networkboot-customiso.

As the network boot is already working, I will try to explain the steps to create the iso and make it available over tftp boot.

• Create an ISO I can boot: (ideally with pre-installed compilers and stuff)
• boot from that ISO -> fight again the UEFI vs BIOS monster.
• add filesystems to my ISO, (ideally I would like to have home in the network, but a local scratchpad mount using the node hdd)

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First attempt

As my ISO is based in Ubuntu16 (don't look at me like that, the man has constraints)  I found a compresive list of steps to follow here: https://help.ubuntu.com/community/LiveCDCustomizationFromScratch

Nevertheless one must fill the gaps when following this document:

prepare the host

The following code creates some sort of fake filesystem and then we can "boot" the fresh system inside:

   mkdir -p work/to_be_sysfs
   cd work
   sudo debootstrap --arch=amd64 xenial to_be_sysfs
   sudo mount --bind /dev to_be_sysfs/dev
   sudo cp /etc/hosts to_be_sysfs/etc/
   sudo cp /etc/resolv.conf to_be_sysfs/etc/
   sudo cp /etc/apt/sources.list to_be_sysfs/etc/apt/
   cat /etc/apt/sources.list
   sudo chroot  to_be_sysfs/

I copied some network configuration and the package manager configuration. no issues here as the target ISO is the same distro version as the host machine.

Inside the Fake Linux:

And then after chroot we are like in a fresh system (so fresh that does not have anything)

inside of chroot:

   mount none -t proc /proc
   cat /proc/cpuinfo    mount none -t sysfs /sys
   mount none -t devpts /dev/pts
   export HOME=/root
   export LC_ALL=C
   sudo add-apt-repository ppa:ubuntu-desktop/ppa
   sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 399B698EEA9EF163B6F9A0F62CC98497A1231595    apt-get update
   apt-get install --yes dbus
   dbus-uuidgen > /var/lib/dbus/machine-id
   cat /var/lib/dbus/machine-id
   dpkg-divert --local --rename --add /sbin/initctl
   apt-get --yes upgrade
   apt-get install --yes ubuntu-standard casper lupin-casper
   apt-get install --yes discover os-prober
   apt-get install --yes linux-generic    apt-get install --yes grub2

here the problems begin, first whit finding out what PPA GPG key to use... but a fast google came out with that one that seems to work, because it downloads stuff.

Then, installing GRUB. it asked questions that were not described in the web, I got pretty scared that I was flashing the boot partition of the host system, I closed my eyes and selected one of the options. Everithing seems to work fine in the host, so it was a success

Back to the host

Now is time to unmount dev partition... but guess what!  it does not.. I can not locate which process keeps the resource busy. But this was fixed with a system reboot (although if the resource was blocked, there should be a reason for it).

    reboot
    cd work/
    sudo umount to_be_sysfs/dev
    sudo apt-get install syslinux squashfs-tools genisoimage
    mkdir -p image/{casper,isolinux,install}
    cp to_be_sysfs/boot/vmlinuz-4.4.0-128-generic image/casper/vmlinuz
    sudo cp to_be_sysfs/boot/vmlinuz-4.4.0-128-generic image/casper/vmlinuz
    sudo cp to_be_sysfs/boot/initrd.img-4.4.0-128-generic image/casper/initrd.lz
    ls to_be_sysfs/boot/
    ls /usr/lib/syslinux/isolinux.bin

And here is where we stop. there is not memtest, and not isolinux... everithing points out that the tutorial was based on some old livecd... and it requires some magic knowledge of the bootstrap process to update it to new distros...

Lets try something else :(

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Second attempt:

I found something else: this seems to be a little more updated: 

https://www.hiroom2.com/2016/06/10/ubuntu-16-04-create-customized-livedvd/

This code is basically the same series of steps, but this time a tool called systemd-nspawn. It is similar to chroot but in this case the new system is booted. I guess we are running in a new process space now, somehow this gives me a better feeling.

Everything runs smoothly until the ISO is generated (I skipped the Japanese keyboard layout as I don't see myself using that).

There was a difference when comparing this method grub script with the one I currently use in PXE or the grub first from the first method. it defines the boot argument of the kernel as live... ok, this is new.... the other one used casper. I may have to learn what is all of this about:

# this one from the live CD

menuentry "Try Ubuntu without installing" {
    set gfxpayload=keep
    linux    /casper/vmlinuz.efi  file=/cdrom/preseed/ubuntu.seed boot=casper quiet splash ---
    initrd    /casper/initrd.lz
}

# this one from my PXE live cd

menuentry "Ubuntu 16 live cd" {
  linux ubuntu-16.04.4-desktop-amd64/casper/vmlinuz.efi root=/dev/nfs boot=casper netboot=nfs nfsroot=10.1.0.1:/srv/tftp/ubuntu-16.04.4-desktop-amd64 splash -- 

  initrd ubuntu-16.04.4-desktop-amd64/casper/initrd.lz
}

# and this one from this second method

serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1
terminal_input console serial
terminal_output console serial

menuentry 'boot the thing' {
  linux /boot/vmlinuz-4.4.0-128-generic boot=live console=tty1 console=ttyS0,115200
  initrd /boot/initrd.img-4.4.0-128-generic
}

the outcome of this one last method was the following: 

maybe not quite there yet...

Conclusion

From here I have some options:

• tweak method 2 to use casper, whatever this means.
• find some other tutorial to follow.
• learn to debug the bootloader.
• boot in a virtual machine first and then move into pxe.
• get myself a cold beer.