Force your Mac to boot into 64 bit mode

UPDATE…

Not all Macs that are capable of booting a 64 bit kernel will boot the 64 bit kernel. The Mini is one of those… (This is from Apple.) Getting those machines NOT on the list to boot into a 64 bit kernel is possible, but it’s beyond the scope of this article (it involves editing your boot.efi.)

Mac Pro (Early 2009)
Mac Pro (Early 2008)

Mac Pro (Original)    
iMac (Early 2009)  
iMac (Early 2008)  
iMac (earlier models)    
Mac mini (all models)    

First, make sure your Mac can support 64 bits. Make sure your server is on the list above too.

ioreg -l -p IODeviceTree | grep firmware-abi

If you are 64 bit capable, you’ll see the following.

| |   "firmware-abi" = <"EFI64">

There are several methods. The easiest method is to hold the 6 and the 4 key when booting. This isn’t permanent, but the following are.

As root, type…

nvram boot-args="arch=x86_64"

To change it back to the default

nvram boot-args=""

I didn’t like this particular method, as I prefer to have a verbose boot

sudo nvram boot-args="-v"

There is one more way, that some people have had more success with. It involves editing /Library/Preferences/SystemConfiguration/com.apple.Boot.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>Kernel</key>
	<string>mach_kernel</string>
	<key>Kernel Flags</key>
	<string></string>
</dict>
</plist>

You need to replace the null value below Kernel Flags () with “arch=x86_64”. The correct version –

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
        <key>Kernel</key>
        <string>mach_kernel</string>
        <key>Kernel Flags</key>
        <string>arch=x86_64</string>
</dict>
</plist>

To check if you’re 64 bit or not, you can use

uname -a

If you see

x86_64

You’ve got a 64 bit kernel.

This also works

system_profiler | grep "64-bit Kernel and Extensions"
      64-bit Kernel and Extensions: Yes