systemd-boot: add 'graceful' configuration option

On some systems bootctl cannot write the `LoaderSystemToken` EFI variable
during installation, which results in a failure to install the boot
loader. Upstream provides a flag (--graceful) to ignore such write failures -
this change exposes it as a configuration option.

As the exact semantics of this option appear to be somewhat volatile it
should be used only if systemd-boot otherwise fails to install.

2 files changed, 26 insertions, 5 deletions

diff --git a/nixos/modules/system/boot/loader/systemd-boot/systemd-boot-builder.py b/nixos/modules/system/boot/loader/systemd-boot/systemd-boot-builder.py
index 7134b432163..6c26b4e0f87 100644
--- a/nixos/modules/system/boot/loader/systemd-boot/systemd-boot-builder.py
+++ b/nixos/modules/system/boot/loader/systemd-boot/systemd-boot-builder.py
@@ -208,10 +208,15 @@ def main() -> None:
         if os.path.exists("@efiSysMountPoint@/loader/loader.conf"):
             os.unlink("@efiSysMountPoint@/loader/loader.conf")
 
-        if "@canTouchEfiVariables@" == "1":
-            subprocess.check_call(["@systemd@/bin/bootctl", "--path=@efiSysMountPoint@", "install"])
-        else:
-            subprocess.check_call(["@systemd@/bin/bootctl", "--path=@efiSysMountPoint@", "--no-variables", "install"])
+        flags = []
+
+        if "@canTouchEfiVariables@" != "1":
+            flags.append("--no-variables")
+
+        if "@graceful@" == "1":
+            flags.append("--graceful")
+
+        subprocess.check_call(["@systemd@/bin/bootctl", "--path=@efiSysMountPoint@"] + flags + ["install"])
     else:
         # Update bootloader to latest if needed
         systemd_version = subprocess.check_output(["@systemd@/bin/bootctl", "--version"], universal_newlines=True).split()[1]
diff --git a/nixos/modules/system/boot/loader/systemd-boot/systemd-boot.nix b/nixos/modules/system/boot/loader/systemd-boot/systemd-boot.nix
index ff304f570d3..0f76d7d6b24 100644
--- a/nixos/modules/system/boot/loader/systemd-boot/systemd-boot.nix
+++ b/nixos/modules/system/boot/loader/systemd-boot/systemd-boot.nix
@@ -24,7 +24,7 @@ let
 
     configurationLimit = if cfg.configurationLimit == null then 0 else cfg.configurationLimit;
 
-    inherit (cfg) consoleMode;
+    inherit (cfg) consoleMode graceful;
 
     inherit (efi) efiSysMountPoint canTouchEfiVariables;
 
@@ -126,6 +126,22 @@ in {
         '';
       };
     };
+
+    graceful = mkOption {
+      default = false;
+
+      type = types.bool;
+
+      description = ''
+        Invoke <literal>bootctl install</literal> with the <literal>--graceful</literal> option,
+        which ignores errors when EFI variables cannot be written or when the EFI System Partition
+        cannot be found. Currently only applies to random seed operations.
+
+        Only enable this option if <literal>systemd-boot</literal> otherwise fails to install, as the
+        scope or implication of the <literal>--graceful</literal> option may change in the future.
+      '';
+    };
+
   };
 
   config = mkIf cfg.enable {