VMWare Fusion: Could not open /dev/vmmon error After updating to Yosemite the only trouble I have is that VMWare Fusion (Professional Version 5.0.5 if that helps) fails to start showing following error:


  Could not open /dev/vmmon: No such file or directory.
  Please make surethat the kernel module `vmmon' is loaded.


I've tried to google the issue but the only relevant thing found was this:


  The Mac has a certain amount of devices it can register in the /dev/ directory ...,  virtual devices like virtualization software and VPN clients also create devices in this directory quickly filling up the number to the limit. To solve this I went through my installed applications and removed every VPN client and VM software that I don’t require any longer and rebooted my machine. After the reboot everything worked immediately.


But even if this is true, I just can not get rid of my VPN client for example. So, I still have no idea what steps I should take to solve the issue. I'll be very much obliged for any hint how to fix this problem.
After having this issue with macOS High Sierra and VMWare Fusion 8.5.8, I was able to resolve it by allowing the system extension as described in http://planetvm.net/blog/?p=3240

In short; open System Preferences, click Security &amp; Privacy, and from the General tab you should see a message stating System software from developer "VMware, Inc." was blocked from loading. Clicking the Allow button resolved the issue for me.