There is issue with Cacti Template on CentOS/RedHat 7 systems.
Problem is “free” binary version.
Percona Cacti Template uses command “free -ob” to retrieve memory state and parse if.
/usr/bin/free binary comes from procps package and there is version difference between CentOS 6 and CentOS 7
CentOS 6 comes with version 3.2.x
CentOS 7 comes with procps-ng version 3.3.x
and CentOS 7 free does not accept -o flag.
So on this systems memory graph is always empty and all returned values from script is -1.