При первом старте сервера.
Linux:
/var/log/cloud-init.log
Windows 2008:
C:\ProgramData\Amazon\Ec2ConfigService\Logs\Ec2ConfigLog.txt
Windows 2012:
C:\ProgramData\Amazon\Ec2Config\Logs\Ec2ConfigLog.txt
Windows 2016:
C:\ProgramData\Amazon\EC-Windows\Launch\UserdataExecution.txt