linux memory: mysql -u zabbix -p -h 127.0.0.1 zabbix -e "select h.name, 100-AVG(hi.value_avg) from hosts h join items i on h.hostid=i.hostid join trends_uint hi on i.itemid=hi.itemid where h.status=0 and i.key_='vm.memory.free.[percent]' and hi.clock