In Mac OS X, how do I partition my hard drive?

Note: In versions of Mac OS X prior to 10.5, or when changing the partition scheme in Mac OS X 10.5, partitioning your hard drive with Disk Utility erases all the information on the drive. In Mac OS X 10.5, as an extra precaution, UITS recommends backing up all of your important files before partitioning your drive.

Mac OS X 10.5 with no changes to the partition scheme

1. In the Applications folder, open Utilities, and then double-click Disk Utility.
   
   
2. In the left column, click the drive you would like to initialize or partition.
   
   
3. To the right, click the Partition tab.
   
   
4. The box beneath "Volume Scheme:" (which should be set to Current) represents your hard disk, where occupied space is shaded. With the handle at the bottom-right of each partition, you can resize the partition by dragging the handle up or down. To add or remove partitions, click the + (plus sign) or - (minus sign) beneath the box. You can assign each partition its own name and file system type.
   
   
5. When you're finished making changes, click Apply.

Mac OS X 10.4 and earlier, or 10.5 with changes to the partition scheme

To partition your startup disk, insert a Mac OS X install disc in your computer, and then restart the computer while holding down the  c  key. When you see the gray Apple logo, release the  c  key. Follow the instructions until you see a menu bar at the top of the screen, and then from the Utilities menu, select Disk Utility.

To partition disks other than your startup disk:

1. In the Applications folder, open Utilities, and then double-click Disk Utility.
   
   
2. In the left column, click the drive you would like to initialize or partition.
   
   
3. To the right, click the Partition tab.
   
   
4. In the drop-down menu under "Volume Scheme:", choose the number of partitions you want to create during the initializing process. For a basic installation of Mac OS X, you need at least one partition.
   
   
5. After you've chosen the number of partitions you want, you can adjust their sizes by dragging the handles that represent the partition borders.
   
   
6. Click each of the partitions to adjust its properties. Under "Volume Information", choose the file system you would like to use. You should usually use Mac OS Extended (Journaled). If you need to access the partition from Windows computers, however, choose MS-DOS.
   
   
7. Click Options... to change the partition scheme. You may need to change this if the disk is meant to be used with Windows computers, or as a startup disk for a Mac with a different architecture. Intel Macs require the GUID Partition Table for their startup disks, while PowerPC Macs use Apple Partition Map. If you need to use the disk with Windows, particularly as a startup disk, choose Master Boot Record. After selecting a scheme, click OK.
   
   
8. When you finish making changes, click Apply or Partition.

Also see:

• In Mac OS X, why can't I unmount my drive to initialize it?
• In Mac OS X, what is First Aid, and when and how should I use it?
• On my Macintosh computer, why can't I format or partition the internal hard drive?