diff -r de2418d11786 -r 85f5444fb7d4 core/src/luan/modules/IoLuan.java
--- a/core/src/luan/modules/IoLuan.java	Thu Jul 14 21:09:55 2016 -0600
+++ b/core/src/luan/modules/IoLuan.java	Fri Jul 15 01:18:01 2016 -0600
@@ -542,6 +542,12 @@
 			return new LuanFile(luan,file.getCanonicalFile()).table();
 		}
 
+		public LuanTable create_temp_file(LuanState luan,String prefix,String suffix) throws LuanException, IOException {
+			File tmp = File.createTempFile(prefix,suffix,file);
+			tmp.deleteOnExit();
+			return new LuanFile(luan,tmp).table();
+		}
+
 		@Override public LuanTable table() {
 			LuanTable tbl = super.table();
 			try {
@@ -581,6 +587,9 @@
 				tbl.rawPut( "canonical", new LuanJavaFunction(
 					LuanFile.class.getMethod( "canonical", LuanState.class ), this
 				) );
+				tbl.rawPut( "create_temp_file", new LuanJavaFunction(
+					LuanFile.class.getMethod( "create_temp_file", LuanState.class, String.class, String.class ), this
+				) );
 			} catch(NoSuchMethodException e) {
 				throw new RuntimeException(e);
 			}

diff -r de2418d11786 -r 85f5444fb7d4 core/src/luan/modules/host/backup.luan
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/core/src/luan/modules/host/backup.luan	Fri Jul 15 01:18:01 2016 -0600
@@ -0,0 +1,18 @@
+local Luan = require "luan:Luan.luan"
+local error = Luan.error
+local Io = require "luan:Io.luan"
+local print = Io.print or error()
+local uri = Io.uri or error()
+local Hosting = require "luan:host/Hosting.luan"
+
+if #{...} ~= 2 then
+	Io.stderr.write "usage: luan luan:host/update.luan domain password\n"
+	return
+end
+
+local domain, password = ...
+
+local zip = Hosting.caller(domain).lucene_backup(password)
+uri("file:backup.zip").write(zip)
+
+print("backed up lucene from "..domain.." to backup.zip")

diff -r de2418d11786 -r 85f5444fb7d4 lucene/src/luan/modules/lucene/Lucene.luan
--- a/lucene/src/luan/modules/lucene/Lucene.luan	Thu Jul 14 21:09:55 2016 -0600
+++ b/lucene/src/luan/modules/lucene/Lucene.luan	Fri Jul 15 01:18:01 2016 -0600
@@ -8,6 +8,8 @@
 local uri = Io.uri or error()
 local String = require "luan:String.luan"
 local matches = String.matches or error()
+local Rpc = require "luan:Rpc.luan"
+local Hosting = require "luan:host/Hosting.luan"
 local LuceneIndex = require "java:luan.modules.lucene.LuceneIndex"
 local NumberFieldParser = require "java:luan.modules.lucene.queryparser.NumberFieldParser"
 local StringFieldParser = require "java:luan.modules.lucene.queryparser.StringFieldParser"
@@ -102,17 +104,31 @@
 	end
 
 	function index.zip(zip_file)
-		matches(zip_file,[[\.zip$]]) or error("file "..zip_file.." doesn't end with '.zip'")
 		index.snapshot( function(dir,file_names)
 			local t = {}
 			for _, file_name in ipairs(file_names) do
 				t[#t+1] = dir.."/"..file_name
 			end
 			local base = uri("file:"..dir).parent().to_string()
-			uri(zip_file).zip(base,t)
+			zip_file.zip(base,t)
 		end )
 	end
 
+	if Rpc.functions.backup == nil then
+		function Rpc.functions.lucene_backup(password)
+			if Hosting.password ~= nil and Hosting.password ~= password then
+				error "wrong password"
+			end
+			local zip_file = uri("file:"..index.dir).parent().child("backup.zip")
+			index.zip(zip_file)
+			return zip_file
+		end
+	else
+		function Rpc.functions.lucene_backup()
+			error "multiple lucene instance"
+		end
+	end
+
 	return index
 end