Added package software-properties-common. it is useful for many apt commands.

Dockerfile

@@ -19,6 +19,8 @@ RUN apt install -y curl wget nano lsb-core nano sudo bash-completion
 
 RUN apt install -y net-tools iputils-ping tcpdump traceroute iproute2 iptables iperf3 dnsutils speedtest-cli
 
+RUN apt install -y software-properties-common
+
 # Installing locales
 RUN apt install -y locales
 ENV LC_ALL en_US.UTF-8