Index: README.release
===================================================================
diff -u -r999de5b9d189aeb6c0e45fdb222d4c962e126762 -r304b0654386d83bae08d088ff67c2ee370fc291f
--- README.release	(.../README.release)	(revision 999de5b9d189aeb6c0e45fdb222d4c962e126762)
+++ README.release	(.../README.release)	(revision 304b0654386d83bae08d088ff67c2ee370fc291f)
@@ -53,8 +53,25 @@
          make test 2>&1|cat |fgrep "definitely lost"
          (8.6b2 ok, when every test returns "40 bytes in 2 blocks")
          (8.6.0 or later ok, when every test returns "0 bytes in 0 blocks")
-
-   - build windows binaries
+       * valgrind via vagrant:
+         1. Install vagrant:  https://www.vagrantup.com/downloads
+	 2. Install VirtualBox: https://www.virtualbox.org/wiki/Downloads
+         3. Check out newest box version: https://app.vagrantup.com/boxes/search?utf8=%E2%9C%93&sort=created&provider=&q=by+chef+bento%2Fubuntu-*+
+	 4. $ mkdir -p ~/VMs/ubuntu-21.04
+	 5. $ cd VMs/ubuntu-21.04
+            $ vagrant init bento/ubuntu-21.04
+            $ vagrant up
+            $ vagrant ssh
+	 6. With box:
+	    vagrant@vagrant:~$ bash
+            vagrant@vagrant:~$ apt update; apt upgrade
+	    vagrant@vagrant:~$ apt install valgrind
+	 7. Setup `apt install tcl-dev` or a custom tcl build
+	 8. vagrant@vagrant:~$ cd nsf && ./configure CFLAGS=-DPURIFY --enable-development
+	 9. Activate valgrind in Makefile (uncomment line with TCLSH plus valgrind)
+	10. vagrant@vagrant:~$ cat valgrind.out | fgrep "definitely lost"
+	11. vagrant@vagrant:~$ cat valgrind.out | fgrep "ERROR SUMMARY" (incl. invalid reads)
+          
    - test tk apps under windows
 
    - Announcement