Does a SUSE Linux Enterprise Server Subscription (maintenance) cover several virtual machines or do we need to purchase a subscription for each virtual machine?

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A SUSE Linux Enterprise Server Subscription is only available on a physical server-basis. Thus, the number of virtual machines running on that server is not important from a software licensing perspective.

Source: Terms and Conditions_SUSE, July 2016

Terms and Conditions Subscription Offerings_SUSE_06-2016Download