docker: fix configure tzdata interaction

Author: cirosantilli

README.adoc

@@ -417,7 +417,7 @@ The very first time you launch Docker, create the container with:
 
 You are now left inside a shell in the Docker guest.
 
-From there, run the exact same commands that you would on a native install: <<getting-started>>
+From there, run the exact same commands that you would on a native install: <<qemu-buildroot-setup>>.
 
 The host git top level directory is mounted inside the guest, which means for example that you can use your host's GUI text editor directly on the files.
 

configure

@@ -78,6 +78,8 @@ pkgs="$pkgs libelf-dev"
 
 # https://stackoverflow.com/questions/20010199/determining-if-a-process-runs-inside-lxc-docker
 if [ -f /.dockerenv ]; then
+  # https://askubuntu.com/questions/909277/avoiding-user-interaction-with-tzdata-when-installing-certbot-in-a-docker-contai
+  export DEBIAN_FRONTEND=noninteractive
   mysudo=
   # https://askubuntu.com/questions/496549/error-you-must-put-some-source-uris-in-your-sources-list
   sed -Ei 's/^# deb-src/deb-src/' /etc/apt/sources.list