If you'd like to see your choices, click the Options button that appears when choosing an installation destination. A dialog sheet appears and presents you with several installation choices, listed below. Here's what each type of installation provides.
Upgrade to Mac OS X, Install Mac OS X
The Installer will present one of the above choices to you, depending on which volume you've selected for installation. If a previous version of Mac OS X is on the selected volume, "Upgrade to Mac OS X" appears (unless the installed version can't be upgraded, as described in this article). If no version of Mac OS X is installed on the volume, "Install Mac OS X" appears.
- About Upgrade to Mac OS X
Upgrading to Mac OS X takes a little longer than installing it on a volume without Mac OS X, but it is the least intrusive way to install--most of your existing settings and applications are left untouched during an upgrade. In other words, you won't have to configure a lot of settings afterwards.
If you're having issues with your currently-installed version of Mac OS X, upgrading may not resolve those issues. Instead, you might benefit more from doing an Archive and Install installation (see "Archive and Install," below).
If you're reinstalling Mac OS X 10.4 or 10.5 on a volume that already contains the same version, you will see Upgrade to Mac OS X as the first choice.
- About Install Mac OS X
Install Mac OS X appears when the installer finds a destination that does not already have Mac OS X installed (or it appears that way). If parts of Mac OS X are missing, this option may appear instead of Upgrade to Mac OS X.
If the selected volume can't be upgraded or software can't be installed on it as is, this choice will be dimmed (unavailable). For example, you can't choose to upgrade or install Mac OS X 10.4 client on a Mac OS X Server 10.3 volume.
Note: If you've updated Mac OS X 10.4 or 10.5 to a later version than what is on your Install disc, you can't use this option, but you can use others described below.
Archive and Install
Select this option if you want to install a "fresh" system on your computer. This type of installation moves existing System files to a folder named Previous System, then installs a new copy of Mac OS X. You cannot start up your computer using the Previous System folder.
Archive and Install installations require the largest amount of available disk space because you need to have room to preserve your existing System and the new one you are installing. This is a good choice if you've already backed up your important files and are trying to resolve an existing issue. Mac OS X-installed applications, such as Address Book and Safari, are archived, and new versions are installed in the Applications folder. For a list of which files are archived, see this article.
Some applications, plug-ins, and other software may have to be reinstalled after an “Archive and Install.” Fonts that were installed in the Fonts folder in the top-level Library folder can be installed in your new system by copying them from the Previous System folder.
About "Preserve Users and Network Settings"
You'll probably want to select the "Preserve Users and Network Settings" checkbox to import your existing accounts' Home folders, and network settings into the new system. Home folders include things such as:
- Files on your desktop and in the Documents folder
- Your personalized preference settings
- Address Book contacts and databases
- Favorite locations and Web browser bookmarks
- iTunes songs and iPhoto pictures
- Your network settings and locations
"Preserve Users and Network Settings" also copies the existing Shared folder in the Users folder to your new system.
Important: Usually it's best to reinstall third-party software after an Archive and Install installation to ensure they work correctly. The "Preserve Users and Network Settings" option leaves non-Apple-installed (third-party) items intact, though they may be moved, depending on their location.
You might wonder "What do I do with the Previous System folder?" It may contain items that you need. To determine this, once you've finished configuring, installing, and updating your applications, you can compare the Previous System to the new System. If there are things in the Previous System folder that aren't in the new System folder, copy them over or reinstall. If you're not sure what some items are (and don't seem to need them), leave them in the Previous System folder. Once you're comfortable that you've got everything you need out of it, you can delete the Previous System folder (or leave it around if you have enough free disk space).
You can’t start up your computer using the Previous System folder, but settings, preference files, fonts, plug-ins, and other items remain available in case you need to access them (which you probably won't, if you use "Preserve Users and Network Settings").
Erase and Install
This option completely erases the destination volume, then installs a new copy of Mac OS X. You should always back up important files on the target volume before using this type of installation.
This is the fastest way to install Mac OS X, but it may take some time to set up your computer after installation. You will have to configure all of your computer settings, install your third-party and iLife applications, and restore your personal files from the backup you made.
Why use this option?
- If you've already backed up your computer, this might be a good choice if you are trying to resolve an existing issue and an Archive and Install installation didn't help.
- This option takes up the least amount of space when the installation is completed.
- This is a good option if you no longer need the information on the computer, and you have another computer that you would like to easily transfer stuff from ("migrate").
Volume format choices
Once you've selected this option, you can choose from two types of volume formats:
- Mac OS Extended (Journaled)—This is the default option and should be used unless you have a specific reason not to.
- UNIX File System—Only choose this option if you specifically need it.
Does an Erase and Install change partition configurations?
No, it uses the current settings. It also doesn't configure advanced RAID settings or perform a secure erase. If you want to do any of these things, use Disk Utility before installing; you can access Disk Utility while started from the Install disc.