nayuos: Update README.

README.md

@@ -19,8 +19,9 @@ in /etc/sudoers:
 ## Input
 In the vifib parameters (softinst\<nb\>.host.vifib.net \> Services \> Parameters):
 
-    * board / ex: peppy, swanky, ... (choosing daisy will accept all licenses for the daisy board build only, in order to use Mali drivers, see [chromium mailing list](https://groups.google.com/a/chromium.org/forum/#!topic/chromium-os-dev/Pf9ZG2itxWM))
-    * branch / ex: release-R46-7390.B
+*   board / ex: peppy, swanky, ... (choosing daisy will accept all licenses for the daisy board build only, in order to use Mali drivers, see [chromium mailing list](https://groups.google.com/a/chromium.org/forum/#!topic/chromium-os-dev/Pf9ZG2itxWM))
+*   branch / ex: release-R46-7390.B
+*   keep_cache / yes|no (choosing "no" saves about 15Go of disk space per board, choosing "yes" will makes next build faster and less expensive in term of needed ressources because of not rebuilding everything)
 
 
 ## Output
@@ -34,5 +35,9 @@ The script that download the sources and build is located in
 
 ## External documents
 
-*   [[ <code>repo</code> command reference ]](https://source.android.com/source/using-repo.html)
-*   [[ NayuOS official website ]](https://www.nayuos.org)
+*   [ <code>repo</code> command reference ](https://source.android.com/source/using-repo.html)
+*   [ NayuOS official website ](https://www.nayuos.org)
+*   [ crouton for chroot ](https://github.com/dnschneid/crouton) ([warning about verified boot](https://github.com/dnschneid/crouton/blob/2a1fc9da380650f47e2bcf37d00962bfb68c4830/installer/main.sh#L517-L536))
+
+## Notes for possible improvements
+*   [ Running virtual machines on your chromebook ](https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/running-virtual-machines-on-your-chromebook)
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