Mac OS X version 10.6, called "Snow Leopard," came out in fall 2009, and was superseded in July 2011 by Lion. Version 10.6.8 of Snow Leopard is still supported by Apple. This note describes how to update a machine with an older version of MacOS to Snow Leopard. The general approach applies to other major OS transitions as well.

If your computer is working now, there is no need to change your OS, although Apple is likely to drop support for 10.5 (Tiger), since they usually support only two versions of the OS. Using an unsupported OS will still work, but if security problems are found in an unsupported version, Apple will not patch them. What you SHOULD do now, whether or not you plan to upgrade:

• Update to OS X 10.5.8 (Leopard) if you have not done so already.
• Use Software Update to keep all Apple software up to date.
• Apply all free updates to other software you use.
• Set up an external hard drive and use  Time Machine.
• If your computer has 1GB of memory or less, add more.
• Fix damaged and duplicate fonts.
• Use Disk Utility to repair permissions on your hard drive.

Why would you want Snow Leopard? If you have an Intel Mac, it will work better and faster with OS X 10.6. Eventually, companies will write software that requires features of the latest OS, and someday you will want to buy and use some of that software. I carefully tried Snow Leopard out on a test computer. I waited to upgrade my main computer until some bugs were fixed. My actual install went smoothly in August 2010, and my machine seems snappier.

Who Can Update

Not everyone can use the new OS version. if you have a PowerPC Mac, OS X 10.6 won't work on it. Stick with 10.5.8.

Plan your install

When you decide to install OS X 10.6, do it carefully. You may find that there are issues that affect you: do your homework.

• Make a list of what hardware and programs you depend on, and search the web to check that they will work.
• Leave yourself enough time. This process will tie up your machine for a big part of a day.

The  Snow Leopard FAQ on http://www.macintouch.com lists a lot of software and whether it will work on OS X 10.6.

When I was getting ready to install 10.6, I found that some software I was using, which worked just fine on 10.5.8, was not compatible with 10.6. I updated most of these old versions with newer versions marked "compatible with Snow Leopard."

Particular issues before upgrading

• If you are using "Classic" programs from Mac OS 9, they are not supported in Snow Leopard (or Leopard).
• Programs that may need paid upgrades: Microsoft Office 2004, Parallels 3.0, Suitcase Fusion.
• Fonts. Damaged or duplicate fonts may cause crashes in 10.6. Check your fonts with FontBook and fix them before upgrading.
• Peripherals. The Apple support forums are full of whining by people whose old printers no longer work. The printer manufacturers have not updated every elderly printer driver for 10.6, and some old printers don't work. It's not Apple's fault, but people are unhappy with Apple. Make sure yours will be supported.

Installing Snow Leopard

1. Clean up and update software before installing
   • Get the applications on your computer ready for 10.6: apply latest fixes.
   • Delete junk files
   • Delete Safari, iTunes, and Firefox caches. I used Cocktail to clean all caches.
   • Empty trash.
   • Repair disk permissions with Disk Utility.
   • Clean up damaged and duplicate fonts.
   • If you modified your Apache configuration, save a copy of /etc/apache2/httpd.conf.
   • If you installed Perl modules via CPAN or fink, make a list of them.
     perldoc perllocal | grep :: and fink list -i | grep -v virtual
2. Backup and prepare
   1. BACK UP YOUR HARD DRIVE to an external disk. I used  SuperDuper to clone my whole drive.
   2. If you use MySQL, backup the database with mysqldump databasename > db.sql
   3. If you use Little Snitch, uninstall it.
3. Install
   • Dismount and unplug external drives.
   • Set screen saver to NEVER, turn the volume way down, and turn off Time Machine.
   • Reboot
   • (Some folks think you should boot from the install disk at this point and run Disk Utility to repair the hard disk. Do this if you suspect there are file system problems.)
   • Use the OS X 10.6 disk to install the new OS. Install Rosetta and Developer Tools from "optional installs." (Takes hours.) (This process will reboot the computer and play some annoying music that you can't quit.)
   • Run Software Update to update to 10.6.8, then run again to make sure all software is updated. (Another hour or two, and another reboot.) (This process hung on one computer I tried it on. I had to restart the computer and retry the install.)
   • Verify that the machine is working OK for you. If you have trouble, restore your backup and go back to 10.5.8.
   • (Mail, printers, WiFi, bluetooth, network, and applications all "just worked" for me.)
4. Recover
   • Wait for Spotlight to finish indexing. Performance will suck till it finishes.
   • Turn on screensaver and Time Machine.
   • If Time Machine complains that it has to discard your old backup and start over, it will do a big backup, takes hours.
   • Repair permissions with Disk Utility again.
   • Note that the display gamma is changed from 1.8 to 2.2 (changed it back on my mini)
   • If you use Little Snitch, re-install and re-register it.
   • In Apple Mail ► Preferences ► Accounts ► Mailbox Behavior, uncheck "Show Notes" for each active account.

Post Install Tasks

• Cocktail: Download and install the Snow Leopard version, and pay for it.
• GraphViz: Download and install the Snow Leopard version.
• 64-bit upgrade: Have to do some extra work if you are upgrading from a 32-bit system to 64-bit. These changes are not urgent but will take advantage of the 64-bit architecture and should run more efficiently.
  • MySQL: see instructions.
  • Perl/CPAN: see instructions.
  • Eclipse 3.6: see instructions.
  • Fink: see instructions.
  • Change your shell environment to export VERSIONER_PERL_PREFER_32_BIT=no to avoid errors from dyld
• Apache
  • Check it. diff httpd.conf, PHP may be turned off, turn it on and make sure it works.
• Epson scanner driver
  • Install driver 3.07A from the Epson support site if not installed already
• Other
  • If you encounter Adobe licensing issues, follow  instructions in the Adobe forum.
  • if Photoshop CS3 crashes on launch, see  this note.

Snow Leopard observations

Gotchas in Snow Leopard

• Mail works differently: if you are composing and hit the "fetch new mail" button it sends the half composed message.
• Address book changed its sort from Last Name to First Name. I changed it back.
• Java's pretty new Basic Authentication dialog box has a checkbox to remember the password, but it always forgets.

Apache

Apache was a pleasant surprise. I had modified /etc/apache2/httpd.conf and all of my mods were applied to the new httpd.conf. Check mod_substitute.so and ServerAdmin, and the LoadModule php5_module statement. It is still wise to save your httpd.conf before updating and compare afterward.

PHP

On occasion I have wanted to test PHP code on my Mac that will be deployed into a protected environment elsewhere. (I am very cautious about PHP because it has historically exhibited multiple security weaknesses. Every day, my websites see dozens to hundreds of attempts to take over the web server by exploiting poorly written PHP functions. Use PHP with care, and don't install PHP code you don't understand.) OS X 10.6 seems to ship with PHP available. If you must use it, php5_module should be loaded, and you need to

• sudo cp /etc/php.ini.default /etc/php.ini
• Edit /etc/php.ini to set date.timezone
• If you need to use it with MySQL, change /var/mysql/ to /tmp/ in three places in /etc/php.ini.
• sudo apachectl restart

AppleScript

AppleScript changed in Snow Leopard. I had an AppleScript, saved in 10.5 as an app. The 10.5 "file" command said "Mach-O executable ppc" even though I saved it on an Intel machine. When moved to 10.6, the file got an icon with a "no entry" slash. Double clicking it got a message saying that the classic environment was not supported.

Script Editor.app is replaced in 10.6 by Utilities:AppleScript Editor.app. The 10.6 AppleScript Editor opened my file but showed garbage in the program text window and got errors. I extracted the program source on Leopard, saved into a text file, pushed it over to Snow Leopard, pasted it into AppleScript Editor, and saved as an app. The resulting app launches OK. It is an application bundle directory, not a file like the old one.

I'm glad I had only one Applescript.. it would be a pain to convert hundreds this way.  Detailed notes from Apple do not mention that old style AppleScript apps won't work.

Planning for the next version

Version 10.7 of Mac OS X, codenamed "Lion," shipped in summer 2011. I wrote a similar web page for upgrading to Lion.