When I first got my home server, a few years back, I spec’d it with a 64bit processor. When I first installed the box I dropped a 64bit version of Linux on it. Pretty soon I realised that some of the additional software I wanted to run on it was not available in 64 bit, so I re-installed a 32 bit version of Linux on it and everything was fine.
The box does LOT of virtualisation both OpenVZ and VMware – with this in mind I recently decided to re-install the 64bit base OS on it and see if I could use some of the Virtualisation Technology thats built into CPUs these days. So this weekend, I backed up all the VMs and moved all the VEs to a different host while I re-installed the server.
It took the best part of a morning to get everything transferred back to the server and get the teething problems resolved. Once I got the VEs back, which was simple (vzmigrate rules), and copied the VMs back I decided to try and create my first 64bit VMware guest. This failed with the message “Your machine does not support long mode, use a 32bit OS”. Now if I wanted a 32bit guest I wouldn’t have gone through all this pain.
Google to the rescue – LOADS of people have had this error and its always been down to the same issue – VT being disabled in the BIOS. Upon checking this was also the case with my server. Im not sure why, when you have Virtualsation Technologies on the CPU, you chose to disable them by default but once I enabled it in the BIOS I was able to create 64bit Hosts (as well as 32bit hosts) on my new server. It (enabling VT) also seem to have brought my initially high load averages back down
To see if your CPU supports VT, if you run Linux, you can check your
/proc/cpuinfo for the existence of either VMX or SVM. It will show up ever if its disabled in the CPU. Try this
egrep '(vmx|svm)' /proc/cpuinfo
The above tip was taken from this site
More info on VT can be found at the wonderful Wikipedia