diff --git a/main.html b/main.html
index e3d5fcd..1dc1751 100644
--- a/main.html
+++ b/main.html
@@ -23,7 +23,7 @@
               <span class="list-group-item list-group-item-danger"> Warning, these default configs will format drives without prompting! </span>
             </div>
             <br /><br />
-            <form action="/process" method="post">
+            <form action="/process" method="post" enctype="multipart/form-data">
                <div class="row">
                     <div class="col">
                         <fieldset class="form-group">
@@ -73,8 +73,15 @@
                     <textarea class="form-control" name="kickstart" onchange="fields_dirty=true">{{ KS_CONTENT }}</textarea>
                 </fieldset>
                 <br />
+                <fieldset class="form-group">
+                    <legend>User data</legend>
+                    <p>Include an arbitrary file on outputted ISO. This file will be placed on the root of the disk.</p>
+                    <input type="file" name="userdata" onchange="fields_dirty=true"/>
+                </fieldset>
+                <br />
                 <input type="submit" value="Build" name="action" class="btn btn-success">
-                <br /><br />
+                <br />
+                <br />
             </div>
         </form>
     </body>
diff --git a/main.py b/main.py
index f48f19b..b351dcc 100755
--- a/main.py
+++ b/main.py
@@ -45,8 +45,9 @@ class ISOserver(object):
                                    BASE_IMAGE=base_image,
                                    **self.samples[sample]))
 
+    # @cherrypy.tools.noBodyProcess()
     @cherrypy.expose
-    def process(self, menu_entries, seed_content, kickstart, base_image, action, sample):
+    def process(self, menu_entries, seed_content, kickstart, base_image, action, sample, userdata):
         assert base_image in self.iso_selection
 
         if action == "Load":
@@ -58,13 +59,21 @@ class ISOserver(object):
             cherrypy.response.headers['Content-Description'] = 'File Transfer'
             cherrypy.response.headers['Content-Disposition'] = 'attachment; filename="{}-custom.iso"'.format(base_image)
 
-            builder = self.isoBuilder(menu_entries, seed_content, kickstart, base_image)
+            builder = self.isoBuilder(menu_entries, seed_content, kickstart, base_image, userdata)
             return builder()
     process._cp_config = {'response.stream': True}
 
-    def isoBuilder(self, menu_entries, seed_content, kickstart, base_image):
+    def isoBuilder(self, menu_entries, seed_content, kickstart, base_image, userdata):
         datadir = os.path.join(self.data_dir, base_image)
 
+        userdata_path = None
+
+        if userdata.file:
+            userdata_name = os.path.basename(userdata.filename)
+            userdata_path = os.path.join(datadir, userdata_name)
+            if os.path.exists(userdata_path):
+                raise Exception("File {} already exists".format(userdata_name))
+
         def output():
             self.builder_semaphores[base_image].acquire()
 
@@ -76,6 +85,14 @@ class ISOserver(object):
                 f.write(kickstart)
 
             try:
+                if userdata.file:
+                    with open(userdata_path, "wb") as f:
+                        while True:
+                            data = userdata.file.read(8192)
+                            if not data:
+                                break
+                            f.write(data)
+
                 proc = Popen(['/usr/bin/mkisofs', '-b', 'isolinux/isolinux.bin', '-c', 'isolinux/boot.cat',
                               '-no-emul-boot', '-boot-load-size', '4', '-boot-info-table', '-J', '-R', '-V',
                               'kickstart_linux', '.'], stdout=PIPE, cwd=datadir)
@@ -86,9 +103,13 @@ class ISOserver(object):
                             break
                         yield data
             except Exception as e:
-                self.builder_semaphores[base_image].release()
                 raise
-            else:
+            finally:
+                if userdata_path:
+                    try:
+                        os.unlink(userdata_path)
+                    except FileNotFoundError:
+                        pass
                 self.builder_semaphores[base_image].release()
 
         return output