NixOS on ARM: Difference between revisions

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== Details about the boot process ==

On NixOS~~, all~~ ARM ~~boards are expected to use U-Boot as the firmware and bootloader. NixOS uses [https:~~/~~/github~~.~~com/u-boot/u-boot/blob/master/doc/develop/distro.rst U-Boot's Generic Distro Configuration Concept] as~~ the ~~mechanism to communicate boot information (such~~ as ~~path to kernel zImage, initrd, DTB, command line arguments)~~. ~~For a quick TL;DR about~~ the ~~generic distro configuration support: U~~-~~Boot is scripted to scan all attached storage devices & partitions and look for~~ a file named <code>/extlinux/extlinux.conf</code> or <code>/boot/extlinux/extlinux.conf</code> (which will be generated by NixOS, just like <code>/boot/grub/grub.cfg</code> is generated on PCs). The partition needs to have its "bootable" flag set.

NixOS can be booted through [[NixOS on ARM/UEFI|UEFI]] on ARM too. The semantics are generally the same as on other architectures. Do note that the common use of Device Tree instead of ACPI in consumer-class hardware ''may'' make this a bit more awkward.

U-Boot ~~also provides an interactive shell~~ and the ~~generation selection menu~~ (~~just like GRUB~~). ~~However,~~ support for ~~input~~ or ~~display devices varies greatly~~, ~~depending~~ on ~~the board~~. ~~Details for what the boards support in relationship~~ to ~~the boot process are detailed in their respective pages~~.

Otherwise, in SBC-class hardware, it is common that boards are generally expected to use U-Boot as the platform firmware and bootloader.

With U-Boot, NixOS currently still assumes use of [https://docs.u-boot.org/en/v2024.04/develop/distro.html U-Boot's Generic Distro Configuration Concept] as the mechanism to communicate boot information (such as path to kernel zImage, initrd, DTB, command line arguments).

For a quick TL;DR about the generic distro configuration support: U-Boot is scripted to scan all attached storage devices & partitions and look for a file named <code>/extlinux/extlinux.conf</code> or <code>/boot/extlinux/extlinux.conf</code> (which will be generated by NixOS, just like <code>/boot/grub/grub.cfg</code> is generated on PCs). The partition needs to have its "bootable" flag set.

== Porting NixOS to new boards ==