Note: Amazon EC2 Windows can get the Windows update either from Microsoft Update Servers or Windows Server Update Services (WSUS). Microsoft Update Servers send updates through the internet. To check your instances' current update source, refer to the following registry key:
Path - HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\AU
Key - UseWUServer, Value - 1
If the UseWUServer key value is 1, then your instances receive updates from WSUS.
If the UseWUServer key value is either 0 or missing, then your instances receive updates from Microsoft Update Servers.
There are several reasons why Windows Update might fail on EC2 instances. Refer to the following troubleshooting steps for common issues. For more information on Windows Update errors, see Windows Update common errors and mitigation on the Microsoft website.
Verify connectivity to the update servers
Microsoft Update servers (internet)
Verify that your instances can reach all Microsoft Update URLs, from the Microsoft website. If the instances can't reach the URLs, then check following conditions:
Instances must have internet connectivity.
Your instances' security group and network access control list (network ACL) must allow traffic on outbound ports 80 and 443.
Check any firewalls or proxy configurations that you applied to the instance. For more information, see Issues related to HTTP/Proxy on the Microsoft website.
Verify that your instances can reach the WSUS server over ports 8530 and 8531 or any custom port that you configured. To do this, run the following PowerShell command:
net start bits
net start wuauserv
net start cryptsvc
Check your system's disk space
Windows Update requires enough free space on your system drive (C:) to download and install necessary files on the instance. Update files vary in size, so make sure that you have sufficient space for the update.
Check any antivirus software
Third-party software such as antivirus or scanning programs might interfere with the update process. They might also corrupt files or cause updates to fail.