nixos-init: read required data from boot.json

nixos/modules/system/activation/nixos-init.nix

@@ -20,28 +20,49 @@ in
     package = lib.mkPackageOption pkgs "nixos-init" { };
   };
 
-  config = lib.mkIf cfg.enable {
-    assertions = [
-      {
-        assertion = config.boot.initrd.systemd.enable;
-        message = "nixos-init can only be used with boot.initrd.systemd.enable";
-      }
-      {
-        assertion = config.system.etc.overlay.enable;
-        message = "nixos-init can only be used with system.etc.overlay.enable";
-      }
-      {
-        assertion = config.services.userborn.enable || config.systemd.sysusers.enable;
-        message = "nixos-init can only be used with services.userborn.enable or systemd.sysusers.enable";
-      }
-      {
-        assertion = config.boot.postBootCommands == "";
-        message = "nixos-init cannot be used with boot.postBootCommands";
-      }
-      {
-        assertion = config.powerManagement.powerUpCommands == "";
-        message = "nixos-init cannot be used with powerManagement.powerUpCommands";
-      }
-    ];
-  };
+  config = lib.mkMerge [
+    {
+      boot.bootspec.extensions = {
+        "org.nixos.nixos-init.v1" = {
+          firmware = "${config.hardware.firmware}/lib/firmware";
+          modprobe_binary = "${pkgs.kmod}/bin/modprobe";
+          nix_store_mount_opts = config.boot.nixStoreMountOpts;
+        }
+        // lib.optionalAttrs (config.environment.binsh != null) {
+          sh_binary = config.environment.binsh;
+        }
+        // lib.optionalAttrs (config.environment.usrbinenv != null) {
+          env_binary = config.environment.usrbinenv;
+        }
+        // lib.optionalAttrs config.system.etc.overlay.enable {
+          etc_metadata_image = config.system.build.etcMetadataImage;
+          etc_basedir = config.system.build.etcBasedir;
+        };
+      };
+    }
+    (lib.mkIf cfg.enable {
+      assertions = [
+        {
+          assertion = config.boot.initrd.systemd.enable;
+          message = "nixos-init can only be used with boot.initrd.systemd.enable";
+        }
+        {
+          assertion = config.system.etc.overlay.enable;
+          message = "nixos-init can only be used with system.etc.overlay.enable";
+        }
+        {
+          assertion = config.services.userborn.enable || config.systemd.sysusers.enable;
+          message = "nixos-init can only be used with services.userborn.enable or systemd.sysusers.enable";
+        }
+        {
+          assertion = config.boot.postBootCommands == "";
+          message = "nixos-init cannot be used with boot.postBootCommands";
+        }
+        {
+          assertion = config.powerManagement.powerUpCommands == "";
+          message = "nixos-init cannot be used with powerManagement.powerUpCommands";
+        }
+      ];
+    })
+  ];
 }

nixos/modules/system/activation/top-level.nix

@@ -33,11 +33,6 @@ let
 
     ln -s ${config.system.build.etc}/etc $out/etc
 
-    ${lib.optionalString config.system.etc.overlay.enable ''
-      ln -s ${config.system.build.etcMetadataImage} $out/etc-metadata-image
-      ln -s ${config.system.build.etcBasedir} $out/etc-basedir
-    ''}
-
     ln -s ${config.system.path} $out/sw
     ln -s "$systemd" $out/systemd
 

nixos/modules/system/boot/systemd/initrd.nix

@@ -733,17 +733,6 @@ in
               cfg.package.util-linux
               config.system.nixos-init.package
             ];
-            environment = {
-              FIRMWARE = "${config.hardware.firmware}/lib/firmware";
-              MODPROBE_BINARY = "${pkgs.kmod}/bin/modprobe";
-              NIX_STORE_MOUNT_OPTS = lib.concatStringsSep "," config.boot.nixStoreMountOpts;
-            }
-            // lib.optionalAttrs (config.environment.usrbinenv != null) {
-              ENV_BINARY = config.environment.usrbinenv;
-            }
-            // lib.optionalAttrs (config.environment.binsh != null) {
-              SH_BINARY = config.environment.binsh;
-            };
             serviceConfig = {
               ExecStart = [
                 ""

pkgs/by-name/ni/nixos-init/Cargo.toml

@@ -7,6 +7,9 @@ edition = "2024"
 anyhow = "1.0.98"
 log = "0.4.27"
 env_logger = { version = "0.11.8", default-features = false }
+serde = { version = "1.0.228", features = ["derive"] }
+serde_json = "1.0.145"
+bootspec = "2.0.0"
 
 [dev-dependencies]
 tempfile = "3.20.0"

pkgs/by-name/ni/nixos-init/src/activate.rs

@@ -1,4 +1,7 @@
-use std::{fs, path::Path};
+use std::{
+    fs,
+    path::{Path, PathBuf},
+};
 
 use anyhow::{Context, Result};
 
@@ -9,7 +12,8 @@ use crate::{config::Config, fs::atomic_symlink};
 /// This runs both during boot and during re-activation initiated by switch-to-configuration.
 pub fn activate(prefix: &str, toplevel: impl AsRef<Path>, config: &Config) -> Result<()> {
     log::info!("Setting up /run/current-system...");
-    atomic_symlink(&toplevel, format!("{prefix}/run/current-system"))?;
+    let system_path = PathBuf::from(prefix).join("run/current-system");
+    atomic_symlink(&toplevel, system_path)?;
 
     log::info!("Setting up modprobe...");
     setup_modprobe(&config.modprobe_binary)?;
@@ -92,17 +96,16 @@ fn setup_firmware_search_path(firmware: impl AsRef<Path>) -> Result<()> {
 ///
 /// We do this here accidentally. `/usr/bin/env` is currently load-bearing for `NixOS`.
 fn setup_usrbinenv(prefix: &str, env_binary: impl AsRef<Path>) -> Result<()> {
-    const USRBINENV_PATH: &str = "/usr/bin/env";
-
-    fs::create_dir_all(format!("{prefix}/usr/bin")).context("Failed to create /usr/bin")?;
-    atomic_symlink(&env_binary, format!("{prefix}{USRBINENV_PATH}"))
+    let usrbin_path = PathBuf::from(prefix).join("usr/bin");
+    fs::create_dir_all(&usrbin_path).context("Failed to create /usr/bin")?;
+    atomic_symlink(&env_binary, usrbin_path.join("env"))
 }
 
 /// Setup /bin/sh.
 ///
 /// `/bin/sh` is an essential part of a Linux system as this path is hardcoded in the `system()` call
 /// from libc. See `man systemd(3)`.
 fn setup_binsh(prefix: &str, sh_binary: impl AsRef<Path>) -> Result<()> {
-    const BINSH_PATH: &str = "/bin/sh";
-    atomic_symlink(&sh_binary, format!("{prefix}{BINSH_PATH}"))
+    let binsh_path = PathBuf::from(prefix).join("bin/sh");
+    atomic_symlink(&sh_binary, binsh_path)
 }