Switching Kernel Boot Mode of a MacBook Pro

On March 14, 2011, in Mac, by Anuj Gakhar

I bought myself the latest and greatest 17′ MacBook Pro this week and the very first problem that I hit after installing some of the Applications from my old Macbook was that one of the apps was not working. The app was “Cisco VPN Client” . The error I was getting was this :-

ERROR 51: Unable to communicate with the VPN subsystem

A quick Google search revealed this post – which makes it clear that the Cisco VPN client only runs in the 32 bit mode. And the new MacBook’s that are coming out in 2011 are being set to boot into the 64 bit kernel mode by default (as far as I understand).

After searching for how to switch the Kernel Mode to 32 bit mode by default, this is what I ended up doing (ofcourse in a Terminal window):-

sudo systemsetup -setkernelbootarchitecture i386

Run this command and reboot the computer – your system is now in the 32 bit kernel mode.

If you want to switch back to the 64 bit kernel mode, you can do this :-
sudo systemsetup -setkernelbootarchitecture x86_64

In order to confirm – what mode you are running in – go to “About this Mac” and then click on “More Info” and on the left hand menu tree – click on the sub menu named “Software” – on the right hand side you will see one of the entries

“64 Bit Kernel and Extensions” – which will be either Yes or No based on what boot setup you have.

Hope this helps someone.

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4 Responses to Switching Kernel Boot Mode of a MacBook Pro

  1. Ken says:

    I found the built-in VPN client to be an excellent replacement for the Cisco client when I started seeing that error. Accessible via the Network preference panel.

  2. Anuj Gakhar says:

    Hi Ken, yes – I saw that as well. However I had to use a pre-loaded Cisco VPN client loaded with all the Profiles and passwords etc….hence the need to use only that one…

  3. Holger says:

    Sure did!!! Big thanks

  4. *very nice post, i surely really like this internet site, maintain on it

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