Your bootloader needs to load kernel, initramfs and dtb into ram at some
offsets, then write these offsets in kernel datastructure (as documented
here https://docs.kernel.org/arch/arm64/booting.html) and finally execute
the kernel.

You didn't specify what device you're booting and what bootloader, but I
can say I've had problems in the past with uboot when trying to boot plain
Image (which uboot calls "legacy" for some reason),
but when packed into FIT image it worked without issues.

As for debugging uart is of course the easiest. Even on phones/tablets
there might be testpoints available.

On Mon, May 18, 2026 at 11:57 AM filip Mutterer <filip@3dds.io> wrote:

> I did -b /mnt and -c /mnt/etc/mkin........
>
> is it possible to let make possition the firmware (dtbs) correctly?
> Right now I only managed to put them into /mnt/boot and there make
> chooses to put it into dtbs folder.
>
> My last compile session gave me a black screen instead of an init error.
> I bet its missing firmware. Having no Display output makes it not
> easier. You have an idea what it could be if screen stays black after
> moving dtbs in place?
>
> On 5/15/26 22:55, Konstantin Kulikov wrote:
> > You can use x86 mkinitfs binary, but you need to set basedir ("-b"
> > flag) to your aarch64 rootfs. And also "-c mkinitfs.conf" cuz it's not
> > prefixed with basedir last time I checked.
>
>