windows sits on the 476g nvme - the disk with three partitions: a 16m
"microsoft reserved" msr with no filesystem, the 476g ntfs c: volume, and
a 832m winre. it has no efi system partition of its own, because it was
installed against the esp that nixos now owns (fs-uuid 5873-AD05). both
oses therefore boot from one shared esp; there is no separate windows
boot drive.
the nixos install reformatted that esp, which wiped
EFI/Microsoft/Boot/{bootmgfw.efi,BCD} and left windows unbootable. that
has since been repaired from winre, so the entry is live. the bcdboot
command is kept in the comment for the next time the esp is reformatted -
it has to run from windows media or winre because the bcd store cannot be
generated from linux, and copying bootmgfw.efi alone fails 0xc000000f.
chainloaded explicitly rather than via grub.useOSProber: deterministic,
pulls in no extra tooling, and avoids probing every disk on each
bootloader install. the -f guard makes the entry self-disabling, so a
future esp reformat degrades to a missing menu item rather than one that
boots into an error. because grub evaluates it at boot rather than at nix
eval time, repairing windows needed no rebuild.
searching by fs-uuid rather than (hdX,gptN) is deliberate: nvme
enumeration is not stable on this board, and /boot has been seen as both
nvme0n1p1 and nvme1n1p1. the -n "$esp" test is a separate nested if
rather than `[ -n "$esp" -a -f ... ]` because grub's test builtin
evaluates both operands of -a instead of short-circuiting, so the
combined form would still expand the path test against an unset device.
ahmza
b7e6418fa6