Merge pull request #79 from hoatle/improvements/#78-xtrabackup-ncat

@ #78 | should make sure xtrabackup has "ncat" installed

xtrabackup/base/Dockerfile

@@ -3,15 +3,20 @@ ARG DEBIAN_VERSION=stretch
 
 FROM debian:$DEBIAN_VERSION
 
+# An ARG declared before the FROM instruction can’t be used after the FROM
+ARG DEBIAN_VERSION
+
 LABEL authors="hoatle <[email protected]>"
 
 # default percona-xtrabackup-80; other possible values: percona-xtrabackup, percona-xtrabackup-24
 ARG XTRABACKUP_PACKAGE=percona-xtrabackup-80
 
+
 RUN apt-get update \
     && apt-get install -y --force-yes \
-        apt-transport-https ca-certificates mariadb-client nmap gnupg lsb-release \
-    && rm -rf /var/lib/apt/lists/*
+        apt-transport-https ca-certificates mariadb-client gnupg lsb-release
+
+RUN if [ "$DEBIAN_VERSION" = "buster" ] ; then apt-get install -y ncat  ; else apt-get install -y nmap ; fi
 
 RUN apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 9334A25F8507EFA5