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How is the ISO image presented to the booting machine via the network? Usually it's not too hard to load kernel/initrd from an ISO via ipxe/http, but then they

by jwiz 3y ago

How is the ISO image presented to the booting machine via the network? Usually it's not too hard to load kernel/initrd from an ISO via ipxe/http, but then they need to have a way to see the ISO themselves.

codetrotter 3y ago
> How is the ISO image presented to the booting machine via the network? Probably in two stages. First a small kernel/initrd is booted with PXE from dhcp+tftp Then that one has the ability to get the iso image either via tftp, or perhaps http or ftp or some other protocol, from the machine that served the initial files over tftp
- jwiz 3y ago
  Yes, that is how you would do it if you are rolling your own boot setup. But, most ISO images are not set up to work this way, and the implication of the iVentoy site is that you can just use unmodified ISO images. That is what I am wondering: How can you use unmodified ISO images to boot, as images, over the network? (Or can you?) All the iPXE forum posts about this idea essentially end with "you can't do that without kernel support for reading the rest of the ISO.", so if iVentoy has solved that, I wanted to know how.
  - codetrotter 3y ago
    The situation is not all that different from their other tool for having multiple ISOs on a usb drive though, is it? You have ISO images that usually you would write onto a CD or write to a USB drive with dd. These cannot boot by themselves if you just put the ISO file as is onto a FAT32 USB drive or similar. But Ventoy has a stage one boot thing for USB which you can then use to select an ISO file from your USB and somehow boot it. So iVentoy would work the same way. The stage one is from iVentoy, not from the ISO itself. And that stage one does something that makes it possible to boot the ISO that it retrieved. Similar to how the USB based thing somehow can boot the ISO files from the USB.
    - jwiz 3y ago
      > does something that makes it possible to boot the ISO The "something" is what I am asking about.
- linsomniac 3y ago
  >either via tftp, or perhaps http or tftp I saw that iVentoy seems to have an NBD server, so it might just be mounting the ISO from the server via NBD.
  - codetrotter 3y ago
    Hadn’t heard about NBD before. > On Linux, network block device (NBD) is a network protocol that can be used to forward a block device (typically a hard disk or partition) from one machine to a second machine. Nice! That makes a lot of sense! https://en.wikipedia.org/wiki/Network_block_device https://en.wikipedia.org/wiki/Network_block_device
  - rtp4me 3y ago
    Indeed, it seems iVentoy uses NBD to present block storage devices (eg: ISOs) to the DHCP client. I just installed iVentoy 1.0.08 in my lab on a Debian 12 VM (via VMware 8 server). From there, I created a new VM and booted Linux Mint 21.1 via UEFI boot. Linux Mint install went well with no noticeable issues. Overall, first impressions are looking good. Found a few bugs that need to get worked out including: * UEFi boot requires iVentoy to have 2 vCPUs (see forums) * Restarting the iVentoy script resets the IP Boot config (specifically the Subnet Mask and Gateway) From their release page, iVentoy supports a bunch of Linux and Windows install images, and you can even inject custom auto-install scripts to the ISO for unattended installs. Very cool. Finally, the iVentoy discussion forum seems very active, and the developer seems engaged. I will probably support the developer ($49) because he was able to leverage NBD to overcome some iPXE issues I struggled with for a long time. I know how much time/effort goes into making iPXE booting look seamless. Kudos to him/her/them
    - jwiz 3y ago
      So, it loads some kind of shim that presents as a BIOS optical drive, but reads its data via NBD? Then, say, the linux kernel of the vanilla ISO installer sees that shim program as a sort of virtual cdrom? When you installed Mint, did you happen to notice from where the installer thought it was reading the files?
    - 3y ago

by jwiz 3y ago

codetrotter 3y ago

> How is the ISO image presented to the booting machine via the network? Probably in two stages. First a small kernel/initrd is booted with PXE from dhcp+tftp Then that one has the ability to get the iso image either via tftp, or perhaps http or ftp or some other protocol, from the machine that served the initial files over tftp

jwiz 3y ago
Yes, that is how you would do it if you are rolling your own boot setup. But, most ISO images are not set up to work this way, and the implication of the iVentoy site is that you can just use unmodified ISO images. That is what I am wondering: How can you use unmodified ISO images to boot, as images, over the network? (Or can you?) All the iPXE forum posts about this idea essentially end with "you can't do that without kernel support for reading the rest of the ISO.", so if iVentoy has solved that, I wanted to know how.
- codetrotter 3y ago
  The situation is not all that different from their other tool for having multiple ISOs on a usb drive though, is it? You have ISO images that usually you would write onto a CD or write to a USB drive with dd. These cannot boot by themselves if you just put the ISO file as is onto a FAT32 USB drive or similar. But Ventoy has a stage one boot thing for USB which you can then use to select an ISO file from your USB and somehow boot it. So iVentoy would work the same way. The stage one is from iVentoy, not from the ISO itself. And that stage one does something that makes it possible to boot the ISO that it retrieved. Similar to how the USB based thing somehow can boot the ISO files from the USB.
  - jwiz 3y ago
    > does something that makes it possible to boot the ISO The "something" is what I am asking about.
linsomniac 3y ago
>either via tftp, or perhaps http or tftp I saw that iVentoy seems to have an NBD server, so it might just be mounting the ISO from the server via NBD.
- codetrotter 3y ago
  Hadn’t heard about NBD before. > On Linux, network block device (NBD) is a network protocol that can be used to forward a block device (typically a hard disk or partition) from one machine to a second machine. Nice! That makes a lot of sense! https://en.wikipedia.org/wiki/Network_block_device https://en.wikipedia.org/wiki/Network_block_device
- rtp4me 3y ago
  Indeed, it seems iVentoy uses NBD to present block storage devices (eg: ISOs) to the DHCP client. I just installed iVentoy 1.0.08 in my lab on a Debian 12 VM (via VMware 8 server). From there, I created a new VM and booted Linux Mint 21.1 via UEFI boot. Linux Mint install went well with no noticeable issues. Overall, first impressions are looking good. Found a few bugs that need to get worked out including: * UEFi boot requires iVentoy to have 2 vCPUs (see forums) * Restarting the iVentoy script resets the IP Boot config (specifically the Subnet Mask and Gateway) From their release page, iVentoy supports a bunch of Linux and Windows install images, and you can even inject custom auto-install scripts to the ISO for unattended installs. Very cool. Finally, the iVentoy discussion forum seems very active, and the developer seems engaged. I will probably support the developer ($49) because he was able to leverage NBD to overcome some iPXE issues I struggled with for a long time. I know how much time/effort goes into making iPXE booting look seamless. Kudos to him/her/them
  - jwiz 3y ago
    So, it loads some kind of shim that presents as a BIOS optical drive, but reads its data via NBD? Then, say, the linux kernel of the vanilla ISO installer sees that shim program as a sort of virtual cdrom? When you installed Mint, did you happen to notice from where the installer thought it was reading the files?
  - 3y ago