Comment on How to Run Custom Linux Images on Oracle Free Tier

• InnerScientist@lemmy.world ⁨1⁩ ⁨day⁩ ago

  Kexec can be used to load a new kernel and “reboot” quickly, it can also be used to load a new kernel, an initrd and never touch the disk. Such a system lives completely in ram and allows you to modify the disk in any way you want without breaking you running Linux (which is in ram)

  Any distro that has a network boot installer that can be passed to kexec can be installed this way, any that don’t can still kexec any Linux distro and then install any other distro by passing the disk to a VM and installing linux through that.

  You can also kexec the netboot.xyz image and get any distro supported there.

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  • starkzarn@infosec.pub ⁨1⁩ ⁨day⁩ ago

    The “gotcha” with Oracle free tier is that you can’t install from arbitrary media, so the typical netboot.xyz or any iPXE workflow is out. No console access, no pre-bootloader access, nothing.

    I’ve been fiddling with kexec, but it doesn’t seem like a supported method of loading the lkrn file from netboot…

    This is super interesting to me, so by all means, if you have the kung-fu to show how this works I would happily read through that!

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    • InnerScientist@lemmy.world ⁨1⁩ ⁨day⁩ ago

      Yeah I tried just now and it diesn’t seem to be working (anymore?) could’ve sworn that worked.

      You can still kexec the installiers directly, I followed the netboot.xyz scripts and got the links they use. Here’s Debian as an example:

      From the scripts: deb.debian.org/debian/dists/…/netboot/ looking at the boot config debian-installer/amd64/grub/grub.cfg

      submenu '... KDE Plasma desktop boot menu ...' {
          set gfxpayload=keep
          menuentry '... Install' {
              set background_color=black
              linux    /debian-installer/amd64/linux desktop=kde vga=788 --- quiet
              initrd   /debian-installer/amd64/initrd.gz
      

      so we need to download those two files and take the netboot.xyz cmdline arguments then

      $ kexec --command-line="desktop=kde vga=788 mirror/suite=Debian13.2 initrd=initrd.magic console=ttyS0,115200n8"  --initrd=initrd.gz -l linux´
      $ systemctl kexec
      

      and it boots.

      also here’s an example for the nixos netboot commands, more on that in the nixos manual:

      $ kexec --load ${SCRIPT_DIR}/bzImage \
        --initrd=${SCRIPT_DIR}/initrd.gz \
        --command-line "init=/nix/store/n37nmcvbrblk9ahfzj9nxy01axs7zsf6-nixos-system-nixos-kexec-25.11pre-git/init nohibernate loglevel=4 lsm=landlock,yama,bpf"
      $ systemctl kexec
      

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      • starkzarn@infosec.pub ⁨1⁩ ⁨day⁩ ago

        Okay this is excellent content, thank you!

        I went through and fiddled with some more stuff to try and get this working to no avail. However, it inspired me to take apart netboot.xyz a bit more, and I was able to grab an efi and get next boot to load the efi file. It took me too long to realize you need the console tty arguments as part of the boot cmdline to get it working interactively, but after I got there I got it netbooted. Sadly though, it almost immediately runs into an OOM condition and thus isn’t practical on a free tier x86 asset. It would probably work on an aarch64 node, but I already have my allotted arm node spun up and working so I don’t have a free one to practice with.

        Solid write-up though, thank you for putting that together!

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