pxe boot and custom kernels

[mdidomenico]

Is there anything special about the kernels and pxe booting? I'm able to get the kernel to load from a raspbian image over pxe. But i can't seem to get any other kernel to pxe. I've tried my own cross-compiled versions using the directions from raspberrypi.org and I've tried extracting the centos arm ported kernel

i can see the pi3 tftp all the requisite files, but it never seems to flip over into the kernel, it just sits there with a blank (disable_splash=1) screen

[DougieLawson]

Does your kernel boot OK on your 3B from a USB stick?

Because that's how I tested PXE with two Raspberries. I got my 2B booted from an SDCard with that bootable USB stick that holds the bootcode/kernel and root fs for my 3B inserted in a USB socket. The 2B runs dnsmasq as the DHCP server and TFTP server. The 3B is wired to the 2B with a straight cat5 cable.

Mount the USB stick partion #2 (/dev/sda2) at /tftp. Mount the USB stick partition #1 (/dev/sda1) at /tftp/boot.

Set up the 2B with a fixed IP address 10.1.2.1 and get it running as an NFS server with /tftp in the exports list.

Run dsnmasq with this config

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port=0
dhcp-range=10.1.2.10,10.1.2.40,300h
log-dhcp
enable-tftp
tftp-root=/tftp/boot
pxe-service=0,"Raspberry Pi Boot"

Have this as /tftp/boot/cmdline.txt

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dwc_otg.lpm_enable=0 console=tty1 root=/dev/nfs nfsroot=10.1.2.1:/tftp elevator=deadline rootwait quiet splash plymouth.ignore-serial-consoles ip=dhcp

Power on the 3B and watch the magic happen.

[asandford]

I've had a custom iscsi build running since last julyish

[mdidomenico]

Yes, the pi will boot just fine from an SD card, with both the raspbian kernel, centos kernel, and my custom kernel. it's just when i try to boot via pxe the kernel fails to load with anything but the raspbian kernel. all of the kernels tftp from the server, but just never hand off from the bootloader, i'm guessing.

[DougieLawson]

What's in config.txt, you can define the kernel to load there. Default is

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kernel=kernel.img

for RPi1, B+, Zero or CM or

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kernel=kernel7.img

for RPi2B, RPI3B & CM3. I'm not sure whether PXE will load an alternative kernel.

[mdidomenico]

I've had set the kernel7.img from the raspbian distro, or set it to one of, either the centos kernel (copied from the /boot partition of the centos arm image) or a custom kernel that i compiled using the directions from the raspberrypi.org website. in the latter cases i can't get the system to pxe those images, but they do boot from the sdcard. the raspbian image works fine.