Hello,
You may create a Unix/Linux shell command monitor to get the alerts if the server uptime is greate than x days.
Please refer to the article below for more details:
https://technet.microsoft.com/en-us/library/jj126087%28v=sc.12%29.aspx
In addition, here is a similar thread for your reference:
https://social.technet.microsoft.com/Forums/windowsserver/en-US/36bb4a52-7012-4de3-b8a0-f8176c633119/linux-servers-uptime-monitoring?forum=operationsmanagerauthoring
Regards,
Yan Li
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