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VMware on AWS - How to restore NSX DFW firewall rules to previous state

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Customers who uses NSX day-in, day-out would like to have a point-in time restore functionality of DFW firewall rules. Many customer have a large footprints in VMC and make changes to DFW quite often. This feature was missing for long time and we could see its included in recent versions . Let's see how DFW configuration roll back works  NSX DFW configuration has versioning, and it is stored in the NSX Manager.  Every time when someone update DFW configuration, NSX creates one more version but keep storing the previous ones. You can rollback for previous config but reapplying it once again.  You can find the options under Networking & Security tab , > Security > Distributed Firewall . In the right side we see an Actions drop down. Choose View to get to the below screen.  Let’s go through the use case:  1. Original state- default config with no custom rules:  a. There are no saved configurations during last 30 days: In my existing test setup, with the current setting

Ntoskrnl.exe is Missing or Corrupt



Ntoskrnl.exe (Windows boot up kernel) is a vital component utilized in the boot process for NT based Microsoft operating systems. It is also responsible for a host of system services such as process and memory management, security management, object management, hardware virtualization and so on. It holds several sub systems: Cache Manager, I/O Manager, Configuration Manager, Local Procedure Call, Memory Manager, Process Structure, Object Manager and Security Reference Monitor. Collectively, they form part of Executive services and System Services. As a result of such critical responsibilities, ntoskrnl.exe is a fundamental constituent of the Windows operating system.
NTOSKRNL.EXE is missing or corrupt

The NTOSKRNL.EXE is missing or corrupt error message is usually encountered during the boot process of NT based Windows operating systems. It can also be classified as a blue screen error, which is a colloquial term coined by users to describe error screens displayed by Windows. These errors are displayed due to critical system errors which may cause the system to shutdown to avoid system damage. This specific error may occur because of common hardware failure, the Ntoskrnl.exe file is missing or corrupt, Windows is not installed in the location mentioned in the boot.ini file and so on.

The NTOSKRNL.EXE is missing or corrupt error message is typically displayed as one of the following:

Windows could not start because of a computer disk hardware configuration problem.

Could not read from the selected boot disk. Check boot path and disk hardware.

Please check the Windows documentation about hardware disk configuration and your hardware reference manuals for additional information.
Windows NT could not start because the following file is missing or corrupt:

Winnt_rootSystem32Ntoskrnl.exe

Please re-install a copy of the above file.
Winnt_rootSystem32Hal.dll missing or corrupt:

Please re-install a copy of the above file.
  • To correct the issue, you can use any one of the following procedures:
  • Procedure 1
  • Before you start the process, go into your BIOS settings and ensure that your CD-ROMdrive has the highest drive priority and not the disk drive or some other drive. Insert the Windows Operating System CD and restart your computer.
  • As the computer is restarting, you will see the message Press any key to boot from the CD. Press any key on your keyboard, such as the Enter key or spacebar.
  • Wait for the setup files to load, and then press R on your keyboard to enter theRecovery Console.
  • Choose the operating system that needs to be fixed, and then enter the Administrator password if you have created one earlier, else press enter.
  • At the recovery console prompt, type the following command :

expand d:i386ntoskrnl.ex_ c:windowssystem32

  • You will be asked whether you wish to overwrite the File. Type Y and press enter.
  • When the file is overwritten and replaced with the ntoskrnl.exe file from the operating system CD and it returns to the command prompt, type exit and press enter. If the file replacement is successful, the computer will reboot normally.

Procedure 2

  • Insert the Windows Operating System CD and restart your computer.
  • As the computer is restarting, you will see the message Press any key to boot from the CD. Press any key on your keyboard, such as the Enter key or space bar.
  • Wait for the setup files to load, and then press R on your keyboard to enter the Recovery Console.
  • Choose the operating system that needs to be fixed, and then enter the Administrator password if you have created one earlier, else press enter.

  • At the recovery console prompt, type the following command :
    CHKDSK /r
    The above command basically finds bad sectors and retrieves readable information.
    When the repair process is complete and it returns to the command prompt, type exitand press enter. If the repair process is successful, your computer will reboot normally.

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