replication - Detecting VM Copied / Replicated -

i looking detect unique constraint if , when vm image copied 1 location another. doing part of product licensing service modification prevent license tampering. licensing service uses mac id uniquely identify license. works fine on physical machine in case of copied vm licensing service unable identify os separate os , invoke license blocking. need unique element gets changed when vm copied / replicated. (i have omitted details on simplification). thoughts appreciated.

the way aware of approach have licensing server. when enter license code client (on vm), contacts server , sends license code , other information. contacts repeatedly (you define interval -- maybe once every few hours) asking 'am still valid"? along request, sends unique id. server replies 'yes, valid', , sends new unique id client. client sends unique id next request server.

if vm duplicated, next time asks server 'am valid?', unique id incorrect either it, or other vm. both not continue work.

you need determine if server goes down, or network goes down, such client cannot communicate server. disable software? bad idea! don't make customers angry. you'll want give them grace period. how long should be? few days? weeks?

let's give them 1-month grace period. in theory, clone parent vm after entering license key, restore other vms clone before grace period runs out, disabling network access them. hassle customers though, have pirated additional copies of software. have determine kind of grace period won't hassle legitimate customers, while giving protection seek.

additional protection achieved verifying vm's clock set correctly. prevent above approach pirating.

another consideration savvy user write own licensing server communicate vm instances, , tell them 'you're good' -- encrypting communication deter this. how far want go here depends on how think pirating might issue customers. in end won't able stop true pirates have time on hands, can keep honest users honest.