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nixos/iso-image: Support systemd initrd #291750

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Merged
emilazy merged 1 commit into from
Aug 10, 2025
Merged

nixos/iso-image: Support systemd initrd #291750

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80 changes: 60 additions & 20 deletions nixos/modules/installer/cd-dvd/iso-image.nix
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
{
config,
lib,
utils,
pkgs,
...
}:
Expand Down Expand Up @@ -785,7 +786,11 @@ in
# specified on the kernel command line, created in the stage 1
# init script.
"/iso" = lib.mkImageMediaOverride {
device = "/dev/root";
device =
if config.boot.initrd.systemd.enable then
"/dev/disk/by-label/${config.isoImage.volumeID}"
else
"/dev/root";
neededForBoot = true;
noCheck = true;
};
Expand All @@ -794,7 +799,7 @@ in
# image) to make this a live CD.
"/nix/.ro-store" = lib.mkImageMediaOverride {
fsType = "squashfs";
device = "/iso/nix-store.squashfs";
device = "${lib.optionalString config.boot.initrd.systemd.enable "/sysroot"}/iso/nix-store.squashfs";
options = [
"loop"
]
Expand All @@ -809,18 +814,11 @@ in
};

"/nix/store" = lib.mkImageMediaOverride {
fsType = "overlay";
device = "overlay";
options = [
"lowerdir=/nix/.ro-store"
"upperdir=/nix/.rw-store/store"
"workdir=/nix/.rw-store/work"
];
depends = [
"/nix/.ro-store"
"/nix/.rw-store/store"
"/nix/.rw-store/work"
];
overlay = {
lowerdir = [ "/nix/.ro-store" ];
upperdir = "/nix/.rw-store/store";
workdir = "/nix/.rw-store/work";
};
};
};

Expand Down Expand Up @@ -882,9 +880,9 @@ in
# UUID of the USB stick. It would be nicer to write
# `root=/dev/disk/by-label/...' here, but UNetbootin doesn't
# recognise that.
boot.kernelParams = [
"root=LABEL=${config.isoImage.volumeID}"
boot.kernelParams = lib.optionals (!config.boot.initrd.systemd.enable) [
"boot.shell_on_fail"
"root=LABEL=${config.isoImage.volumeID}"
];

fileSystems = config.lib.isoFileSystems;
Expand All @@ -901,6 +899,44 @@ in
"overlay"
];

boot.initrd.systemd = lib.mkIf config.boot.initrd.systemd.enable {
emergencyAccess = true;

# Most of util-linux is not included by default.
initrdBin = [ config.boot.initrd.systemd.package.util-linux ];
services.copytoram = {
description = "Copy ISO contents to RAM";
requiredBy = [ "initrd.target" ];
before = [
"${utils.escapeSystemdPath "/sysroot/nix/.ro-store"}.mount"
"initrd-switch-root.target"
];
unitConfig = {
RequiresMountsFor = "/sysroot/iso";
ConditionKernelCommandLine = "copytoram";
};
serviceConfig = {
Type = "oneshot";
RemainAfterExit = true;
};
path = [
pkgs.coreutils
config.boot.initrd.systemd.package.util-linux
];
script = ''
device=$(findmnt -n -o SOURCE --target /sysroot/iso)
fsSize=$(blockdev --getsize64 "$device" || stat -Lc '%s' "$device")
mkdir -p /tmp-iso
mount --bind --make-private /sysroot/iso /tmp-iso
umount /sysroot/iso
mount -t tmpfs -o size="$fsSize" tmpfs /sysroot/iso
cp -r /tmp-iso/* /sysroot/iso/
umount /tmp-iso
rm -r /tmp-iso
'';
};
};
Comment on lines +905 to +938
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@emilazy emilazy Aug 1, 2025

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(This is kind of gross, but I realize that doing anything about it is out of scope for this PR.)


# Closures to be copied to the Nix store on the CD, namely the init
# script and the top-level system configuration directory.
isoImage.storeContents = [
Expand Down Expand Up @@ -958,15 +994,19 @@ in
source = "${efiDir}/EFI";
target = "/EFI";
}
{
source = (pkgs.writeTextDir "grub/loopback.cfg" "source /EFI/BOOT/grub.cfg") + "/grub";
target = "/boot/grub";
}
{
source = config.isoImage.efiSplashImage;
target = "/EFI/BOOT/efi-background.png";
}
]
++ lib.optionals (config.isoImage.makeEfiBootable && !config.boot.initrd.systemd.enable) [
# http://www.supergrubdisk.org/wiki/Loopback.cfg
# This feature will be removed, and thus is not supported by systemd initrd
{
source = (pkgs.writeTextDir "grub/loopback.cfg" "source /EFI/BOOT/grub.cfg") + "/grub";
target = "/boot/grub";
}
]
++ lib.optionals (config.boot.loader.grub.memtest86.enable && config.isoImage.makeBiosBootable) [
{
source = "${pkgs.memtest86plus}/memtest.bin";
Expand Down
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