Switching to Snow Leopard (SL)

Mac OS 10.6 aka Snow Leopard

Unfortunately I wasn't fast enough snatching one of the popular copies of SL at the local store. After waiting four cruelly days I got my copy and spent another day preparing my system for installation. In contrast to the opinion that only windows users have to format their hard disk when installing a new system I chose that way because I like the nerdy 'fresh' feeling of a vanilla system :)

Installation ran smoothly on my unibody MBP. In addition to the installation of several applications I manually copied settings and application data from a time machine backup:

• Address Book (/Library/Application Support/AddressBook)
• iCal (/Library/Calendars)
• Mail (/Library/Mail)
• Safari (/Library/Safari)
• VirtualBox (/Library/VirtualBox)

- et voilà, it works! (basically at least)

Deleting Time Machine Backup

After manually copying the latest Time Machine backup (@see /Backups.backupdb) to a safe location I tried to purge the Time Machine backup dir. Moving that dir to trash and emptying trash results in an error. Also a simple sudo rm -rdf Backups.backupdb doesn't work. The reason is that apple uses Access Control Lists (ACLs) for Time Machine backups as you can read here and here. After spending a night trying to delete that skit I reconnected Time Machine to my Leopard backup an manually deleted each backup :-/ The remove all option didn't worked for me (nothing happened).

Activate 64-bit Kernel

SL brings 64-bit to the kernel. But you have to activate it manually! Out of the box only applications run in 64-bit mode, the kernel is 32-bit. The actual configuration can be checked by

1. Choose Apple menu > About This Mac.
2. Click More Info to open System Profiler. (Or open the Apple System Profiler application located in /Applications/Utilities.)
3. Click the topic 'Software' on the left. On the right hand you can read the value of '64-bit kernel and extensions'.

To activate the 64-bit kernel follow these steps:

Test your CPU
Not every CPU is capable of running the kernel in 64-bit mode. Open a console and type

ioreg -l -p IODeviceTree | grep firmware-abi
If the output contains the string EFI64 then your CPU is ready for the 64-bit kernel.

Testrun the 64-bit kernel

There are some secret keys with SL. When booting the machine, press 6 4 (at the same time) to boot the 64-bit kernel. (If you are using the 64-bit kernel by default you can press 3 2 (at the same time) to boot the 32-bit kernel.)

Make changes permanent

If you feel comfortable running the 64-bit kernel (here are some benchmarks) edit the file

/Library/Preferences/SystemConfiguration/com.apple.Boot.plist

to make changes permanent.

Change the key Kernel Flags to the value arch=x86_64. That's all. (but beware of the side effects)

Side Effects

Installing MySQL 5.1 x86_64 from .DMG doesn't work actually because the .DMG is packed with the HFS file system, which is a 32-bit kernel extension and doesn't run on the 64-bit kernel. Workaround: Boot with the magic keys 3 2 and install mysql. Reboot and you're fine.

Another glitch is that the Safari hack Safari Stand does not work with 64-bit (workaround). It is build on SIMBL (32-bit) which is an InputManager, but InputManagers have to be 64-bit with the 64-bit kernel. Update: Yesterday a new Snow Leopard ready beta of SIMBL was released - but I haven't tried it out yet.