diff --git a/common/utils.cc b/common/utils.cc
index 19c63c0..166cfb4 100644
--- a/common/utils.cc
+++ b/common/utils.cc
@@ -87,6 +87,11 @@
 // The path to the kernel's boot_id.
 const char kBootIdPath[] = "/proc/sys/kernel/random/boot_id";
 
+// A pointer to a null-terminated string containing the root directory where all
+// the temporary files should be created. If null, the system default is used
+// instead.
+const char* root_temp_dir = nullptr;
+
 // Return true if |disk_name| is an MTD or a UBI device. Note that this test is
 // simply based on the name of the device.
 bool IsMtdDeviceName(const string& disk_name) {
@@ -143,13 +148,17 @@
   }
 
   base::FilePath temp_dir;
+  if (root_temp_dir) {
+    temp_dir = base::FilePath(root_temp_dir);
+  } else {
 #ifdef __ANDROID__
-  temp_dir = base::FilePath(constants::kNonVolatileDirectory).Append("tmp");
+    temp_dir = base::FilePath(constants::kNonVolatileDirectory).Append("tmp");
+#else
+    TEST_AND_RETURN_FALSE(base::GetTempDir(&temp_dir));
+#endif  // __ANDROID__
+  }
   if (!base::PathExists(temp_dir))
     TEST_AND_RETURN_FALSE(base::CreateDirectory(temp_dir));
-#else
-  TEST_AND_RETURN_FALSE(base::GetTempDir(&temp_dir));
-#endif  // __ANDROID__
   *template_path = temp_dir.Append(path);
   return true;
 }
@@ -158,6 +167,10 @@
 
 namespace utils {
 
+void SetRootTempDir(const char* new_root_temp_dir) {
+  root_temp_dir = new_root_temp_dir;
+}
+
 string ParseECVersion(string input_line) {
   base::TrimWhitespaceASCII(input_line, base::TRIM_ALL, &input_line);