diff --git a/metropolis/pkg/efivarfs/efivarfs.go b/metropolis/pkg/efivarfs/efivarfs.go
new file mode 100644
index 0000000..90c4519
--- /dev/null
+++ b/metropolis/pkg/efivarfs/efivarfs.go
@@ -0,0 +1,74 @@
+// Copyright 2020 The Monogon Project Authors.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// This package was written with the aim of easing efivarfs integration.
+//
+// https://www.kernel.org/doc/html/latest/filesystems/efivarfs.html
+package efivarfs
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"path/filepath"
+	"strings"
+
+	"golang.org/x/text/encoding/unicode"
+)
+
+const (
+	Path       = "/sys/firmware/efi/efivars"
+	GlobalGuid = "8be4df61-93ca-11d2-aa0d-00e098032b8c"
+)
+
+// ExtractString returns EFI variable data based on raw variable file contents.
+// It returns string-represented data, or an error.
+func ExtractString(contents []byte) (string, error) {
+	// Fail if total length is shorter than attribute length.
+	if len(contents) < 4 {
+		return "", fmt.Errorf("contents too short.")
+	}
+	// efiUnicode defines the Unicode encoding used by UEFI which is UCS-2
+	// Little Endian. For BMP characters UTF-16 is equivalent to UCS-2.
+	// See the UEFI Spec 2.9, Sections 33.2.6 and 1.8.1.
+	efiUnicode := unicode.UTF16(unicode.LittleEndian, unicode.IgnoreBOM)
+	// Skip attributes, see @linux//Documentation/filesystems:efivarfs.rst for format
+	efiVarData := contents[4:]
+	espUUIDNullTerminated, err := efiUnicode.NewDecoder().Bytes(efiVarData)
+	if err != nil {
+		// Pass the decoding error unwrapped.
+		return "", err
+	}
+	// Remove the null suffix.
+	return string(bytes.TrimSuffix(espUUIDNullTerminated, []byte{0})), nil
+}
+
+// ReadLoaderDevicePartUUID reads the ESP UUID from an EFI variable. It
+// depends on efivarfs being already mounted. It returns a correct lowercase
+// UUID, or an error.
+func ReadLoaderDevicePartUUID() (string, error) {
+	// Read the EFI variable file containing the ESP UUID.
+	espUuidPath := filepath.Join(Path, "LoaderDevicePartUUID-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f")
+	efiVar, err := ioutil.ReadFile(espUuidPath)
+	if err != nil {
+		return "", fmt.Errorf("couldn't read the LoaderDevicePartUUID file at %q: %w", espUuidPath, err)
+	}
+	contents, err := ExtractString(efiVar)
+	if err != nil {
+		return "", fmt.Errorf("couldn't decode an EFI variable: %w", err)
+	}
+	return strings.ToLower(contents), nil
+}