This is not exactly a Linux question, as we're dealing with pre-Linux stage. Hopefully, someone could shed some light nevertheless.

I'm able to boot a board with a USB thumb drive (containing a Linux .hddimg) from AMI BIOS. Processor is Intel Xeon D. What're the key configuration changes I need in BIOS to make it boot from "external LAN"? This BIOS apparently support Legacy mode and UEFI mode.

In my BIOS it's Boot > Boot to Network (the Boot menu of the BIOS)

You should be able to set it in the boot order in the BIOS.

Network boot should be one of the boot devices in the 'boot' menu.

Yes, I realize it's in the boot order. I set it to both "internal LAN" and "external LAN", but neither works. Every time, it drops back to the BIOS menu (because of failure). I know my network connection works, as after Linux initializes, I could use it. So, what else I may need? The LAN also has DHCP server configured (as again when Linux is UP, that's how the board gets its IP address). Do you use legacy mode, or UEFI? Or either way would work? How do you debug this kind of issue?

Uefi means that you can configure bios to configure and set ip addresses in efi shell. (usually)

It should also mean that it supports some sort of pxe(lan) boot.

One can usually get some media or flash some software to boot to gpxe/ipxe.

Okay. I'm able to see a new "screen" that I'd never been able to see before. I'm able to get to "grub". There's a bunch of commands that I'll look into. The changes I made to make this happen are:

1. In BIOS, when "Other USB Device" is still chosen as 1st boot device (and has USB thumb drive with a bootable Linux image on it), I choose "Serial Console Install" option when the system is on its way up. This leads to creation of new partitions and copying of the boot image over to my SSD.

2. In BIOS, change boot priority to use "UEFI Standard" instead of "Legacy Type". The BIOS menu is updated to show 1st boot device as the SSD previously already installed.

I'm not sure if #1 is really needed, but in any case, these 2 steps get me to do without the USB thumb drive (I'm able to boot from SSD), and give new grub shell that I could explore to see how it may work with network booting. I know I need to look into PXE booting as well.

You are mixing up grub and uefi and even legacy mode maybe.

Maybe we need to start over. What are you trying to do exactly?

In many bio's you have to enable pxe boot from some choice and then it may allow a boot order choice.

Grub is like efi shell in many ways. It is not really an OS as such but a mini OS that is used before the OS. Grub means you have booted to some media already after bios has loaded. Grub and now uefi are advanced tools for booting and configuration of hardware.

I started with an eval platform. At that point, all I cared/needed was to quickly boot up the board so I could check out other stuffs. After some experimentation, I got USB boot working with the BIOS.

However, that isn't an approach that could be productized. I also need to see how an installed SSD could be used as a boot device. When a system is blank with nothing on its SSD (except with BIOS on ROM/flash), I need to find out how to populate the system with a bootable initial version of S/W. Presumably, network based booting is preferred to install that first copy.

Yes, GRUB, UEFI and BIOS are all new to me. So is network-based booting with BIOS/UEFI. It'd be good if there's some online primer on the topics (I found GRUB 2 web page, and am reading).

@jefro. Thanks for your comments/questions. In light of that, I disconnect the only boot device from the system, and I could see the boot-up now drops to an interactive SHELL, something I couldn't see/do before. So now, I could explore that, instead of GRUB. As you said, having access to GRUB means I already get past initial image install stage, and thus probably isn't something I should be looking into.

Well, maybe. Grub and syslinux did have some work on being able to pxe boot and I don't recall how far it is. Since you are at efi shell then it means you have an ability and need to use uefi methods. It also means that normal business and server systems tend to have pxe enabled in the nic. Usually some bios setting to enable things like wake on lan and boot from lan but not always. Usually a boot order choice for lan.

I'm back and am stuck. Here's a summary of current status/issue -

Intel Xeon-D processor board connected directly to a Linux server. I'm trying to make PXE boot work on my Intel board.

PXE client side -
1. Enabled PXE boot option ROM. It's AMI based BIOS.
2. Selected Type-based boot priority, with 1st boot device = "External LAN"
[I've also tried EFI Standard boot priority, but it didn't help]

PXE server side -
1. Configured DHCP server (ISC DHCP 4.1.1), tftp server.
2. Firewall turned OFF (service iptables stop).
3. DHCP server is configured to listen to "eth0", the interface that my board is connected to.
4. pxelinux.0 for my board's Linux distro is copied to /tftpboot directory (consistent with tftp server's setup).
5. PXE boot DHCP options set (I think, after referencing a number of online materials).
6. I've not configured FTP server (as some source suggested) or NFS; could this be a problem? How does the client know it should use NFS or ftp without getting any config from server (e.g. kickstart config)?

Status:
With tcpdump, I verified that both ends finish the 4-message DHCP exchanges. PXE client successfully downloaded pxelinux.0. But that's all. There's no more tftp messages captured on server side beyond the transfer of pxelinux.0. On the client side, I get this error:

>>Checking Media Presence......
>>Media Present......
>>Start PXE over IPv4. Press ESC key to abort PXE boot.
Station IP address is 192.168.1.12

Server IP address is 192.168.1.1
NBP filename is pxelinux.0
NBP filesize is 46909 Bytes

>>Checking Media Presence......
>>Media Present......
Downloading NBP file...

Succeed to download NBP file.
ERROR: Boot option loading failed

I've run cksum on pxelinux.0 to make sure it's not corrupted compared to the "source". Does anyone have any idea what could have gone wrong here?

Thanks,
Raymond