How to solve the error code 0x800f0818: Feature installation failed in Windows Server 2012 R2

There are several steps you can take to solve the error code 0x800f0818:

1. Check for updates: Make sure your Windows Server 2012 R2 is up to date with the latest updates. Go to Settings > Update & Security > Windows Update and click on Check for updates.
2. Use the DISM tool: Open Command Prompt as an administrator and type the following command: DISM /Online /Cleanup-Image /RestoreHealth. This will scan your system for any corrupted files and repair them.
3. Use the System File Checker tool: Open Command Prompt as an administrator and type the following command: sfc /scannow. This will scan your system for any corrupted system files and repair them.
4. Disable antivirus software: Sometimes antivirus software can interfere with the installation of features. Try disabling your antivirus software temporarily and then try installing the feature again.
5. Use the Windows Server installation media: If none of the above steps work, try using the Windows Server installation media to install the feature. Insert the installation media and run the setup.exe file. Choose the option to upgrade your current installation and follow the prompts to complete the installation.