README: disconnect the builder from the Internet before building

Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/README.txt b/README.txt
index 52b1f0e..a61b21c 100644
--- a/README.txt
+++ b/README.txt
@@ -212,6 +212,27 @@ bytes).
 So you also need to make sure to have at least about 220 GiB of free space
 before starting the build.
 
+Preventing fetching unknown code:
+--------------------------------
+In Replicant 6 we found that some nonfree code was downloaded through maven
+during the build.
+
+While that has been removed as part of the removal of the nonfree ambient SDK
+removal, it is a good practice to prevent the builder from fetching code while
+building to be able to more easily detect issues like that in the future.
+Since the builders had network access here we only found out by all that after
+being notified of the issue  through the Replicant mailing list by someone who
+also removed it in another Android distribution.
+
+If you need to access your builder through SSH, and that you have it on a local
+network, you could simply get the default route and remove it:
+# ip route
+default via 192.168.1.1 dev eth0
+# ip route del default via 192.168.1.1 dev eth0
+
+Or you could simply disconnect it from the network completely and use a
+keyboard, mouse and monitor to interact with it to launch and monitor the build.
+
 Building the images:
 --------------------
 At this point, you can finally start building all the images with