Use 18.04 sources.list as template.

3.New_server_deployment/4.APT_upgrade/0_setup.sh

@@ -15,11 +15,11 @@ fi
 # update sources.list
 rm -f /etc/apt/sources.list~
 echo "Updating /etc/apt/sources.list file."
-cp sources16.list /etc/apt/sources.list
+cp sources.list /etc/apt/sources.list
 if ( rgrep '14.04' /etc/lsb-release >/dev/null ); then
-	sed -i 's@xenial@trusty@' /etc/apt/sources.list
-elif ( rgrep '18.04' /etc/lsb-release >/dev/null ); then
-	sed -i 's@xenial@bionic@' /etc/apt/sources.list
+	sed -i 's@bionic@trusty@' /etc/apt/sources.list
+elif ( rgrep '16.04' /etc/lsb-release >/dev/null ); then
+	sed -i 's@bionic@xenial@' /etc/apt/sources.list
 fi
 
 # modify sources.list to use ubicast cache

3.New_server_deployment/4.APT_upgrade/sources.list

+deb http://archive.ubuntu.com/ubuntu/ bionic           main restricted universe multiverse
+deb http://archive.ubuntu.com/ubuntu/ bionic-updates   main restricted universe multiverse
+deb http://archive.ubuntu.com/ubuntu/ bionic-backports main restricted universe multiverse
+deb http://security.ubuntu.com/ubuntu bionic-security  main restricted universe multiverse
\ No newline at end of file

3.New_server_deployment/4.APT_upgrade/sources16.list

-deb http://archive.ubuntu.com/ubuntu/ xenial           main restricted universe multiverse
-deb http://archive.ubuntu.com/ubuntu/ xenial-updates   main restricted universe multiverse
-deb http://archive.ubuntu.com/ubuntu/ xenial-backports main restricted universe multiverse
-deb http://security.ubuntu.com/ubuntu xenial-security  main restricted universe multiverse
\ No newline at end of file