Today I had some troubles after installing VMWare Fusion 5, whenever I tried to start a virtual machine I got the error “Could not open /dev/vmmon: No such file or directory”, when I tried to Google for this I came across several solutions but none of them could fix my problem.
After hours of searching and trying out stuff I decided to check out what happened in this forum thread; http://communities.vmware.com/message/2168538
To make it quick; The Mac has a certain amount of devices it can register in the /dev/ directory (if someone knows the exact number please let me know in the comments), 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, and even though it took more time than I was hoping for, I’m happy it worked out!
If you want to know more about virtualization have a look at my post Vagrant, because there is no place like /home!