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Since I won't get a better chance to find knowledgeable people: How exactly does iPXE work? Lets say I want to boot a random old PC from one of these images - d

Since I won't get a better chance to find knowledgeable people: How exactly does iPXE work? Lets say I want to boot a random old PC from one of these images - does the bios need to have iPXE support? Or PXE? Or does it need to first boot into some local system first, which then goes out and gets the image to boot the rest of the way from? Then there's mention of DHCP and self hosting. Do I need to have some service running within my LAN first or can this go right out to some public server and boot from images there? How does DHCP factor in? I am in so far over my head on this but it seems interesting and something fun to try out.

bongodongobob 2y ago
Read the docs, it's all there. Edit: Seriously? You click on docs and almost all of those questions are answered. It's 1 click away. Parent didn't even try.
- LoganDark 2y ago
  Which docs? The netboot.xyz ones?
  - bongodongobob 2y ago
    Yes. It's one click away for the overview and the quick start is very good as well.
    - LoganDark 2y ago
      That's great if you want a tutorial, I guess. "How does this work" is different from a tutorial though, IMHO.
- notanormalnerd 2y ago
  I found the netboot docs very hard to understand if you dont have a existing knowledge of PXE.
  - bongodongobob 2y ago
    Has HN turned into a Facebook group?
teraflop 2y ago
There are a bunch of different options to "bootstrap" iPXE in the first place. Least invasive is probably to boot it from a USB drive. You can also set up a traditional PXE boot process using DHCP/TFTP on your network to "chain-load" iPXE (if your client's network card supports PXE), or you can even flash iPXE into the boot ROM on certain network cards. However you do it, once iPXE starts running, it will take control of the NIC and fetch the actual OS images that it needs from the internet over HTTP.
- Joe_Cool 2y ago
  Some HP server UEFIs also support boot from http. So you can boot the .efi executable directly from the internet. For https you need to enroll the certificate first and it's a bit more involved. I am sure there are other implementations I have only seen it on HP servers so far.
hmaxwell 2y ago
You can use netboot.xyz from a flash drive to boot various operating systems and utilities. Alternatively, PXE (Preboot Execution Environment) has been around for a while and works by allowing a network-capable device to boot from its network interface. A PXE-compatible network card requests a DHCP lease during the boot process, which provides the IP address of a TFTP (Trivial File Transfer Protocol) server and the file that needs to be loaded from the server. Typically, the network card contains a basic PXE kernel. To enhance this environment, you can chainload iPXE, which offers a broader range of features. iPXE allows for more advanced booting options, such as loading scripts or initiating an unattended installation directly from the network.
mynameisvlad 2y ago
There's multiple ways to boot, including USB/ISO: https://netboot.xyz/docs/category/booting-methods https://netboot.xyz/docs/category/booting-methods Generally speaking, if you have iPXE already compiled and flashed onto your NIC, then you can follow these instructions: https://netboot.xyz/docs/booting/ipxe https://netboot.xyz/docs/booting/ipxe DHCP is only needed for getting an IP address. You can use the Docker image with the proper DHCP parameters to load it automatically when using PXE/iPXE: https://netboot.xyz/docs/docker https://netboot.xyz/docs/docker
breppp 2y ago
Roughly from memory iPXE is a bootable image that acts similar to a PXE BIOS, so you boot to that image like a regular disk. It acts like a bios by for example hooking your interrupts for storage reads. In order to find where the image is, you need some kind of discovery mechanism. This is where DHCP comes in. Remember this is all happening before you have an OS, so it has to be very bare bones
NobodyNada 2y ago
PXE [0] is a standard for netbooting, typically implementated in the system's boot firmware. A PXE-compatible client sends a DHCP request on boot, to which the network's DHCP server responds with the IP address of a server to netboot from. The client will then connect to this server via TFTP, download an executable image file in the PXE format, and boot it. Using PXE on your own computer requires enabling PXE the firmware setup, setting up a TFTP server to serve the PXE image, and configuring your DHCP server to point to your TFTP server. iPXE [1] is an open-source implementation of PXE, and much more -- it's much more flexible, it supports additional protocols including HTTP(S) and DNS, it has configuration and scripting options, a basic command-line interface, etc. In order to run iPXE, you need to boot an iPXE image somehow -- e.g. from a MBR or EFI image on a disk drive or USB drive (or even over PXE, I guess). But because iPXE supports more protocols and more configuration, you don't need to set up TFTP and DHCP, and it can chainload into e.g. an EFI image or a Linux kernel instead of being limited to booting images in the PXE format. An example of iPXE in the wild is the Arch Linux netboot image [2]. They provide pre-configured iPXE images that display an interactive menu to select a mirror, download the Arch Linux installer, and boot it. (It's really convenient since you can just drop the UEFI image at "/efi/boot/bootx64.efi" on a FAT32 thumb drive instead of having to download the whole installer image and 'dd' it onto the drive.) The submitted project, netboot.xyz, is a similar idea: a preconfigured build of iPXE that lets you interactively download and boot installers for many popular operating systems from a single image. [0]: https://en.wikipedia.org/wiki/Preboot_Execution_Environment https://en.wikipedia.org/wiki/Preboot_Execution_Environment [1]: https://ipxe.org/ https://ipxe.org/ [2]: https://archlinux.org/releng/netboot/ https://archlinux.org/releng/netboot/
- ddulaney 2y ago
  > or even over PXE, I guess This is super common actually! Most built-in PXE only supports TFTP, which is pretty slow compared to TCP-based stuff. It can make sense to use the built-in PXE to grab a (small) iPXE image over TFTP, then have iPXE grab the (big) real image over HTTP(S). This is also useful if you want to store your main image on something like S3 that doesn’t support TFTP. For a while I had a script that would create iPXE images dynamically on the fly with the correct HTTPS URL and auth information embedded in them.
- 2y ago
gsich 2y ago
You usually chainload from normal PXE if you have hardware.
anon291 2y ago
So what I do here is that I have a local PXE server (it's a DHCP option on your router) that serves up iPXE with a preconfigured script to boot via HTTP off of netboot.xyz. So whenever I want to install linux on a new computer, I set the BIOS boot option to boot from PXE next boot and restart. In a few seconds, I am presented with my choice of linux environment. For my data center servers, I have it booting via PXE to an iPXE with a custom script to take a unique identifier from the host and build the corresponding configuration (NixOS). So essentially for that I define my NixOS configuration in a NixOS flake and plug the new host in and it will boot to the correct configuration. I actually don't have any OS installation on most of the hosts and share the nix store via NFS. I also keep an iPXE thumb drive around in case I need to do this for something not on my network. In that case, I insert the drive, boot from it, and then ask it to boot from netboot.xyz manually.
alfiedotwtf 2y ago
If you want to see how all the magic happens, have a look at the code and docs from Debian’s FAI (Fully Automated Install). Once you have a Debian FAI all setup, you can bootstrap your machine from zero every morning while you have your morning coffee
RulerOf 2y ago
Since nobody directly answered some of your specific questions: > Lets say I want to boot a random old PC from one of these images - does the bios need to have iPXE support? Or PXE? The most-desirable way to use iPXE is to boot it from a system's built-in PXE, chainloading it from a local DCHP+TFTP server. All routers have a DHCP server, and many enthusiast/professional routers will have a TFTP server available. pfSense/OPNSense for example can both do this. If you want to go down the rabbit hole and can mod your system BIOS, you can install iPXE into many of them. I wouldn't recommend it, but I did it once and thought it was pretty cool. > random old PC If you _literally_ meant like a vintage PC that predates the PXE spec[1], you can boot iPXE from any local media — I architected a project 10 years ago where I actually gave floppy disks to technicians because some of the ancient Dells we were working with required a BIOS update to enable USB booting. You can also burn iPXE into a network card's ROM chip. There were a lot of PCI/ISA network cards that took an EEPROM and could boot from them if populated. I always thought it would be fun to boot a vintage PC with iPXE straight off of an add-in network card like that. iPXE will hook the BIOS, and you can literally boot MS-DOS via iSCSI. > Do I need to have some service running within my LAN first or can this go right out to some public server and boot from images there? Again, typical deployments will have iPXE chainloaded from the system's existing PXE implementation, which means you've got a DHCP server on the local segment, and a TFTP server somewhere on the local network. But you _could_ boot iPXE from any other boot medium, which would mean the DHCP/TFTP setup are not required. iPXE itself, once loaded, can do its work with any network connection. [1]: https://en.wikipedia.org/wiki/Wired_for_Management https://en.wikipedia.org/wiki/Wired_for_Management - this happened in 1998/1999 and implementation was widespread by 2001 or so.

bongodongobob 2y ago

Read the docs, it's all there. Edit: Seriously? You click on docs and almost all of those questions are answered. It's 1 click away. Parent didn't even try.

LoganDark 2y ago
Which docs? The netboot.xyz ones?
- bongodongobob 2y ago
  Yes. It's one click away for the overview and the quick start is very good as well.
  - LoganDark 2y ago
    That's great if you want a tutorial, I guess. "How does this work" is different from a tutorial though, IMHO.
notanormalnerd 2y ago
I found the netboot docs very hard to understand if you dont have a existing knowledge of PXE.
- bongodongobob 2y ago
  Has HN turned into a Facebook group?

teraflop 2y ago

There are a bunch of different options to "bootstrap" iPXE in the first place. Least invasive is probably to boot it from a USB drive. You can also set up a traditional PXE boot process using DHCP/TFTP on your network to "chain-load" iPXE (if your client's network card supports PXE), or you can even flash iPXE into the boot ROM on certain network cards. However you do it, once iPXE starts running, it will take control of the NIC and fetch the actual OS images that it needs from the internet over HTTP.

Joe_Cool 2y ago
Some HP server UEFIs also support boot from http. So you can boot the .efi executable directly from the internet. For https you need to enroll the certificate first and it's a bit more involved. I am sure there are other implementations I have only seen it on HP servers so far.

hmaxwell 2y ago

You can use netboot.xyz from a flash drive to boot various operating systems and utilities. Alternatively, PXE (Preboot Execution Environment) has been around for a while and works by allowing a network-capable device to boot from its network interface. A PXE-compatible network card requests a DHCP lease during the boot process, which provides the IP address of a TFTP (Trivial File Transfer Protocol) server and the file that needs to be loaded from the server. Typically, the network card contains a basic PXE kernel. To enhance this environment, you can chainload iPXE, which offers a broader range of features. iPXE allows for more advanced booting options, such as loading scripts or initiating an unattended installation directly from the network.

mynameisvlad 2y ago

There's multiple ways to boot, including USB/ISO: https://netboot.xyz/docs/category/booting-methods https://netboot.xyz/docs/category/booting-methods Generally speaking, if you have iPXE already compiled and flashed onto your NIC, then you can follow these instructions: https://netboot.xyz/docs/booting/ipxe https://netboot.xyz/docs/booting/ipxe DHCP is only needed for getting an IP address. You can use the Docker image with the proper DHCP parameters to load it automatically when using PXE/iPXE: https://netboot.xyz/docs/docker https://netboot.xyz/docs/docker

breppp 2y ago

Roughly from memory iPXE is a bootable image that acts similar to a PXE BIOS, so you boot to that image like a regular disk. It acts like a bios by for example hooking your interrupts for storage reads. In order to find where the image is, you need some kind of discovery mechanism. This is where DHCP comes in. Remember this is all happening before you have an OS, so it has to be very bare bones

NobodyNada 2y ago

PXE [0] is a standard for netbooting, typically implementated in the system's boot firmware. A PXE-compatible client sends a DHCP request on boot, to which the network's DHCP server responds with the IP address of a server to netboot from. The client will then connect to this server via TFTP, download an executable image file in the PXE format, and boot it. Using PXE on your own computer requires enabling PXE the firmware setup, setting up a TFTP server to serve the PXE image, and configuring your DHCP server to point to your TFTP server. iPXE [1] is an open-source implementation of PXE, and much more -- it's much more flexible, it supports additional protocols including HTTP(S) and DNS, it has configuration and scripting options, a basic command-line interface, etc. In order to run iPXE, you need to boot an iPXE image somehow -- e.g. from a MBR or EFI image on a disk drive or USB drive (or even over PXE, I guess). But because iPXE supports more protocols and more configuration, you don't need to set up TFTP and DHCP, and it can chainload into e.g. an EFI image or a Linux kernel instead of being limited to booting images in the PXE format. An example of iPXE in the wild is the Arch Linux netboot image [2]. They provide pre-configured iPXE images that display an interactive menu to select a mirror, download the Arch Linux installer, and boot it. (It's really convenient since you can just drop the UEFI image at "/efi/boot/bootx64.efi" on a FAT32 thumb drive instead of having to download the whole installer image and 'dd' it onto the drive.) The submitted project, netboot.xyz, is a similar idea: a preconfigured build of iPXE that lets you interactively download and boot installers for many popular operating systems from a single image. [0]: https://en.wikipedia.org/wiki/Preboot_Execution_Environment https://en.wikipedia.org/wiki/Preboot_Execution_Environment [1]: https://ipxe.org/ https://ipxe.org/ [2]: https://archlinux.org/releng/netboot/ https://archlinux.org/releng/netboot/

ddulaney 2y ago
> or even over PXE, I guess This is super common actually! Most built-in PXE only supports TFTP, which is pretty slow compared to TCP-based stuff. It can make sense to use the built-in PXE to grab a (small) iPXE image over TFTP, then have iPXE grab the (big) real image over HTTP(S). This is also useful if you want to store your main image on something like S3 that doesn’t support TFTP. For a while I had a script that would create iPXE images dynamically on the fly with the correct HTTPS URL and auth information embedded in them.
2y ago

gsich 2y ago

You usually chainload from normal PXE if you have hardware.

anon291 2y ago

So what I do here is that I have a local PXE server (it's a DHCP option on your router) that serves up iPXE with a preconfigured script to boot via HTTP off of netboot.xyz. So whenever I want to install linux on a new computer, I set the BIOS boot option to boot from PXE next boot and restart. In a few seconds, I am presented with my choice of linux environment. For my data center servers, I have it booting via PXE to an iPXE with a custom script to take a unique identifier from the host and build the corresponding configuration (NixOS). So essentially for that I define my NixOS configuration in a NixOS flake and plug the new host in and it will boot to the correct configuration. I actually don't have any OS installation on most of the hosts and share the nix store via NFS. I also keep an iPXE thumb drive around in case I need to do this for something not on my network. In that case, I insert the drive, boot from it, and then ask it to boot from netboot.xyz manually.

alfiedotwtf 2y ago

If you want to see how all the magic happens, have a look at the code and docs from Debian’s FAI (Fully Automated Install). Once you have a Debian FAI all setup, you can bootstrap your machine from zero every morning while you have your morning coffee

RulerOf 2y ago

Since nobody directly answered some of your specific questions: > Lets say I want to boot a random old PC from one of these images - does the bios need to have iPXE support? Or PXE? The most-desirable way to use iPXE is to boot it from a system's built-in PXE, chainloading it from a local DCHP+TFTP server. All routers have a DHCP server, and many enthusiast/professional routers will have a TFTP server available. pfSense/OPNSense for example can both do this. If you want to go down the rabbit hole and can mod your system BIOS, you can install iPXE into many of them. I wouldn't recommend it, but I did it once and thought it was pretty cool. > random old PC If you _literally_ meant like a vintage PC that predates the PXE spec[1], you can boot iPXE from any local media — I architected a project 10 years ago where I actually gave floppy disks to technicians because some of the ancient Dells we were working with required a BIOS update to enable USB booting. You can also burn iPXE into a network card's ROM chip. There were a lot of PCI/ISA network cards that took an EEPROM and could boot from them if populated. I always thought it would be fun to boot a vintage PC with iPXE straight off of an add-in network card like that. iPXE will hook the BIOS, and you can literally boot MS-DOS via iSCSI. > Do I need to have some service running within my LAN first or can this go right out to some public server and boot from images there? Again, typical deployments will have iPXE chainloaded from the system's existing PXE implementation, which means you've got a DHCP server on the local segment, and a TFTP server somewhere on the local network. But you _could_ boot iPXE from any other boot medium, which would mean the DHCP/TFTP setup are not required. iPXE itself, once loaded, can do its work with any network connection. [1]: https://en.wikipedia.org/wiki/Wired_for_Management https://en.wikipedia.org/wiki/Wired_for_Management - this happened in 1998/1999 and implementation was widespread by 2001 or so.