diff --git a/3.New_server_deployment/3.APT_upgrade/0_setup.sh b/3.New_server_deployment/3.APT_upgrade/0_setup.sh
index bc9c853abf11d392db601ecdb5a84e8f9ba2fad8..cc5d36118fc7b9a6b1c9155d3564c0a7a52a2666 100755
--- a/3.New_server_deployment/3.APT_upgrade/0_setup.sh
+++ b/3.New_server_deployment/3.APT_upgrade/0_setup.sh
@@ -13,15 +13,21 @@ if [ -f '/etc/apt/apt.conf.d/50unattended-upgrades.ucf-dist' ]; then
 fi
 
 # update sources.list
+if ( ! test -f '/etc/apt/sources.list.save' ); then
+	cp -a '/etc/apt/sources.list' '/etc/apt/sources.list.save'
+fi
 rm -f /etc/apt/sources.list~
 if ( lsb_release -a | grep 'Ubuntu' >/dev/null 2>&1 ); then
-	echo "Updating /etc/apt/sources.list file."
-	cp sources.list /etc/apt/sources.list
+	echo 'Updating /etc/apt/sources.list file.'
+	cp 'sources-ubu.list' '/etc/apt/sources.list'
 	if ( lsb_release -a | grep '14.04' >/dev/null 2>&1 ); then
 		sed -i 's@bionic@trusty@' /etc/apt/sources.list
 	elif ( lsb_release -a | grep '16.04' >/dev/null 2>&1 ); then
 		sed -i 's@bionic@xenial@' /etc/apt/sources.list
 	fi
+else
+	# Debian
+	cp 'sources-deb.list' '/etc/apt/sources.list'
 fi
 
 # modify sources.list to use ubicast cache
diff --git a/3.New_server_deployment/3.APT_upgrade/sources-deb.list b/3.New_server_deployment/3.APT_upgrade/sources-deb.list
new file mode 100644
index 0000000000000000000000000000000000000000..09940822f79666568dd15b4ead11c1f4e6ff12a5
--- /dev/null
+++ b/3.New_server_deployment/3.APT_upgrade/sources-deb.list
@@ -0,0 +1,5 @@
+deb http://ftp.debian.org/debian buster main contrib non-free
+
+deb http://ftp.debian.org/debian buster-updates main contrib non-free
+
+deb http://security.debian.org buster/updates main contrib non-free
diff --git a/3.New_server_deployment/3.APT_upgrade/sources.list b/3.New_server_deployment/3.APT_upgrade/sources-ubu.list
similarity index 92%
rename from 3.New_server_deployment/3.APT_upgrade/sources.list
rename to 3.New_server_deployment/3.APT_upgrade/sources-ubu.list
index 06433ad75c9fcca5f3471b4ab6401d8e126a0a51..cc10e6e4eaf014df85e4bcf6f8c399924f4fbd28 100644
--- a/3.New_server_deployment/3.APT_upgrade/sources.list
+++ b/3.New_server_deployment/3.APT_upgrade/sources-ubu.list
@@ -1,4 +1,4 @@
 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
+deb http://security.ubuntu.com/ubuntu bionic-security  main restricted universe multiverse