diff --git a/src/hosts.zig b/src/hosts.zig
index 041528b..8748e9a 100644
--- a/src/hosts.zig
+++ b/src/hosts.zig
@@ -3,7 +3,7 @@ const util = @import("util.zig");
 
 const hosts_header = "# local-etc-hosts-updater";
 
-const FILE_LINE_BUFF_SIZE = 50;
+const FILE_LINE_BUFF_SIZE = 100;
 
 pub fn update_hosts(ip: util.IP) !void {
     try create_tmp_hosts(ip);
@@ -107,4 +107,17 @@ fn create_tmp_hosts(ip: util.IP) !void {
     }
 }
 
-fn move_tmp_hosts() !void {}
+fn move_tmp_hosts() !void {
+    var target_hosts = try std.fs.createFileAbsoluteZ(try util.getenv("OLD_HOSTS_PATH"), .{ .lock = .exclusive });
+    defer target_hosts.close();
+    const target_writer = target_hosts.writer();
+    var tmp_hosts = try std.fs.openFileAbsoluteZ(try util.getenv("TMP_HOSTS_PATH"), .{});
+    defer tmp_hosts.close();
+    const source_reader = tmp_hosts.reader();
+
+    source_reader.streamUntilDelimiter(target_writer, 0x00, null) catch |err| {
+        if (err != error.EndOfStream) {
+            return err;
+        }
+    };
+}