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A sparse image is a type of disk image file used on Mac OS X that grows in size as the user adds data to the image, taking up only as much disk space as stored in it. Encrypted sparse image files are used to secure a user's home directory by the FileVault feature in Mac OS X Snow Leopard and earlier. Sparse images can be created using Disk Utility.〔(【引用サイトリンク】 title=Disk Utility 12.x: Create a disk image )〕 Unlike a full image file (.dmg), which takes up as much actual space as the real disk it represents (regardless of the amount of unused space), a sparse image file (.sparseimage) takes up only as much actual disk space as the data contained within, up to a maximum of the capacity assigned during creating.〔(【引用サイトリンク】 title=Disk Utility 12.x: Disk image formats )〕 ==Limitations== Two limitations are therefore worth noting regarding the use of this image file format: # A customized ".sparseimage" image file can be assigned a larger total capacity than the physical volume (or HD partition) on which it originally resides. While the virtual volume will seem to make that capacity available, attempting to exceed the physical capacity of the underlying volume will result in a disk error: "ran out of space". The .sparseimage file must first be moved to a larger physical disk or partition. # As noted above, while mounted .sparseimage image files automatically expand to their preassigned limit when data is added, they cannot be arbitrarily resized without the use of Disk Utility, hdiutil, or other such software.〔(【引用サイトリンク】 title=Disk Utility 12.x: Resize a disk image )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sparse image」の詳細全文を読む スポンサード リンク
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