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The only argument that is required for lacutil is the activation key. The hostid HostID of the current machine will be used automatically, if the hostid is HostID is required. There is also an option to print out hostids HostIDs of the machine and eventually specify them manually, which can let you activate a license locked to a different machine than the current one.
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Activate a license by specifying the activation key, with the hostid HostID selected automatically from the current machine:
lacutil.exe -activate -act_key X34UT-0B2VE-1LAT9-Y3S45
Activate a license by specifying the activation key and a hostid HostID list:
lacutil.exe -activate -act_key X34UT-0B2VE-1LAT9-Y3S45 -hostid ETHERNET=DABA9F60077CBD89,BIOS=Y2DVL2
Print out a hostid HostID list for the current machine:
lacutil.exe -hostid