Oracle VirtualBox Guest Addons | kernel headers not found for target kernel

So how many Oracle VirtualBox VM (Virtual Machine)s you do have?

I’ve many. I try many new software & not to break production box, I try them using Virtual Machines. I use Oracle VirtualBox (mostly) for both Windows and Linux machines (and VMWare ESXi for Production servers), as you could see with the above image. VirtualBox and VMWare supply additional software called “Guest Additions” that synchronize the Guest Virtual Machines with Host machine seamlessly. Like Mouse integration that allows your mouse to travel between both host and guest machines without any difficulties.

On Linux OS, installing the Guest Additions could be sometimes challenging. Especially with Oracle Linux that uses UEK kernels. Let us see how to “fix” the common error messages that appears when installing the Guest Additions on Oracle Linux 7 and 8.

The best approach is to update your Linux OS with latest patches before trying the below. I consider you already updated your Linux box, if yes then

yum install kernel-uek-devel

is enough to install the devel package, suffice the kernel headers missing error. Install the package, reboot the box and try to install VirtualBox Guest Additions. This time module should get installed properly. You may need make, gcc & perl already installed for a successful installation of Guest Additions. You will find instructions to install them later in the article.

Now we have another situation when guest add-ons are required, however updating the new Linux box is not possible due to many reasons. Here we will use the Linux OS ISO image. Please note, the ISO file that you are going to use must be the same ISO that you used to install OS and OS was not updated at all. That means your Linux box is as it is after the OS installation.

Attach the ISO file to your Linux box & Switch to

Packages folder for Oracle Linux 7 and “BaseOS\Packages” for Linux 8

Now locate the kernel-uek-devel-xxxxxxxxxxxxxxxxxxxx package and install it. For example, I will execute the following for Linux 8

rpm -ivh kernel-uek-devel-5.4.17-2136.300.7.el8uek.x86_64.rpm

That’s it. Restart the box and try to install the guest add-ons once again and you must be through without other issues. You might need to install gcc, make & perl also to get the guest add-ons installed.

If you are connected to internet, you can install the above packages by issuing the command

yum install gcc make perl -y

Or go through the packages available in the Packages repo, install them.

All the best!

KB5009543 | Jan 2022 cumulative update breaks IKEv2 VPN Connections

KB5009543 or Cumulative update Jan 2022 for Windows 10 and Windows 11 is currently breaking IKEv2 VPN connections. If you are experiencing an unexpected connection failure with a vague error message like “General processing error”, please follow the below steps.

Go to Program and Features -> Installed Updates and uninstall KB5009543. Reboot the box and the VPN connection should start working normally. Optionally you may disable the Windows Update for a period of time so that the same update will not get installed once again. Please note, Microsoft releases updates to their products quite often to resolve issues those were identified. Few times these updates open new issues, like the one happened with this particular KB.

While there are no straight forward methods available to “stop” Windows updates, you can use multiple methods to disable Windows update completely, which we don’t recommend. One of them is using group policies on the local machine.

If you still consider disabling Windows updates temporarily/long term, please refer this excellent tutorial

Hope this helps.

Slow SSH connections from Windows to Linux hosts

Windows built-in firewall does not block SSH connections those are going out & there is no need to create an exception for SSH connections from Windows to LINUX hosts. Still many things could mess up connections.

One of the major culprits being the DNS settings. We had a migration for Primary domain controller from 2008 R2 to Windows Server 2016. Prior the upgrade we brought a temporary VM using VirtualBox to insure that the migration could happen seamlessly. The migration to temporary server happened without issues and we rushed to change the DNS settings for all production servers with the new VM IP address, after removing the IP address for the old PDC from the list.

After the confirmations, we built a fresh VM on VMWare ESXi environment and promoted it as PDC & we ahead with decommissioning the VM built on VirtualBox and forgot that “one thing”. Changing DNS server details for our LINUX servers.

Initially we didn’t give much attention to the SSH connection slowness as these LINUX server(s) running Oracle Applications were known to be slow in responding. However, things didn’t look quite promising as we noticed delays like 40s+ to establish connection to the host while trying to upload files using FileZilla client. It took us almost 8 days to realize that the connection issues were not from the client end, rather from the servers.

Checking the network configurations revealed these servers were still configured with the IP address of the temporary DC at the first entry, that we had for a while. Resetting the DNS entries to existing DNS servers IP addresses resolved the problems instantly.

Side note: No, you cannot overcome this issue by using IP addresses to establish the SSH connection. Regardless, the Linux HOST will try to resolve the client’s IP using the given DNS entries. So the only solution was to correct the DNS entries!

If you ever run into a slow SSH, well, hope know where to look at first after reading this post.