The boot volume on Mac OS X based computers is listed with the name Macintosh HD in the Disk Utility, in case you did not change it earlier. The name specifies that the particular volume contains Mac OS X installation and you must be careful while dealing with it. In odd situations, your Mac may not be able to boot from this drive and you have to either repair it or reboot it with Mac OS X bootable DVD.
Mac OS X lets you partition its hard drive into several volumes, aiming for storing different types of data in separate volumes. This enables you to keep your data organized and access with ease. Based on some practical scenarios, users often resize their Mac volumes when they need to enlarge or shrink them, based on their storage needs. However, what if you need to enlarge Mac boot volume, i.e. Macintosh HD? Can you resize Mac boot drive without having to fret over data loss or Mac boot failure? Intel-based Mac machines let you do this with Disk Utility or a reliable partition manager.
Why to Resize Boot Volume?
Well, this is a big question that why you would resize the boot volume of your Mac. However, you might be in need for installing more applications and the boot volume is lacking the required space. Alternatively, you may shrink the boot volume in order to enlarge a secondary volume that contains your personal stuff.
The usage of disk management tool (whether Disk Utility or an external partition manager) is your choice, I will cover resizing the scenario with both the tools.
Note: Before you begin with the task, I suggest booting from Recovery HD for Mac Lion, Mountain Lion, or Mavericks. Users of earlier versions of Mac can boot from Mac Bootable DVD.
Boot from Recovery HD
1. Restart your Mac machine and hold down the Command + R keys right after you hear the startup tone.
2. As you see the startup screen, leave the keys.
3. Select Recovery HD when appears, and then click the arrow button pointing downwards.
Boot from Mac Bootable DVD
1. Insert Mac Bootable DVD into the playing media and restart your Mac.
2. Hold down the ‘C’ key to boot from the bootable DVD.
3. Leave the key when you see the startup screen.
4. In Mac OS X Utilities screen, select Disk Utility.
Using Disk Utility
1. Highlight the hard drive containing Macintosh HD drive in the left pane, and then click the Partition tab in the right pane.
(In the Partition tab, you will see a graphical view of your Mac hard drive. The blue color in each partition indicates data, while white color indicates the free space.)
2. Highlight the Macintosh HD volume and hold it from its bottom right corner and do the following:
◦ Drag the volume upwards to shrink it.
◦ Drag the volume downwards to enlarge it.
3. With the desired changes done, click Apply button to save them.
Note: Disk Utility causes wastage of free space if you shrink a volume. Besides, you cannot enlarge any of the volumes even if you have free space available on the hard drive.
Using Partition Manager
A number of professional tools to manage partitions on Mac are available on the Internet. However, you must be very careful while choosing one out of them, as an inefficient partition manager may cause data loss while resizing a volume. With the partition manager downloaded from the Internet, select your Mac partition and specify a new size for this volume.
A professional partition manager enables you use the free space available on the hard drive and enlarge the required volumes. Therefore, I suggest using a professional partition manager to avoid wastage of free space as well as for efficient partitioning.