- By Kevin M. White
- Oct 29, 2009
This chapter is from the book
- What is the difference between disk drives, partitions, and volumes?
- What are the two primary partition schemes for Mac-formatted drives? What are their differences?
- What are the six volume formats supported by Mac OS X? How are they different?
- How does file system journaling work?
- What are the four erase options available in Disk Utility? What are the differences between them?
- How does the Finder’s Secure Empty Trash feature work?
- What three methods can be used to eject a volume or drive from the Finder?
- What is the potential side effect of improperly unmounting or ejecting a drive or volume?
- What differentiates a RAID 0 set from a RAID 1 set?
- How do you use the Finder’s burn folder feature?
- How do you use Disk Utility to burn an optical disc?
- Why is the root, or beginning, level of a user’s home folder visible to other users?
- How are the permissions on the Shared folder set to allow for local user sharing?
- How does the default organization of the file system allow users to safely share local files and folders?
- What does it mean when you choose the option to “ignore volume ownership” in the Finder? What are the security ramifications of ignoring volume ownership?
- How do you identify the ownership and permissions of a file or folder in the Finder? In the Terminal?
- How do permissions in the Finder appear different than permissions in the Terminal?
- What is the sticky bit?
- How is Disk Utility’s Verify and Repair feature used?
- What is target disk mode and how is it engaged?
- Disk drives are the actual storage hardware, partitions are logical divisions of a disk drive used to define the storage space, and volumes, contained inside partitions, are used to define how the individual files and folders are saved to the storage.
- GUID Partition Table is the default partition scheme on Intel-based Macs, and Apple Partition Map is the default partition scheme on PowerPC-based Macs.
- The volume formats supported as startup volumes for Mac OS X are Mac OS X Extended, the native volume format supported by all Macintosh computers; Mac OS X Extended, Journaled, the default volume format for Mac OS X drives; and Mac OS X Extended, Journaled, Case-Sensitive, the default volume format for Mac OS X Server drives. Volume formats supported as read/write are Mac OS Standard (HFS), a legacy Mac OS volume format; UNIX File System (UFS), a legacy volume format supported by many other UNIX-based systems; and File Allocation Table (FAT32), the volume format used by many peripherals and older Windows-based PCs. Volume formats supported as read-only: NT File System (NTFS), the native volume format used by modern Windows-based operating systems; ISO 9660, a common format for CD media; and Universal Disk Format (UDF), a common format for DVD media.
- File system journaling records what file operations are in progress at any given moment. This way, if a power failure or system crash occurs, after the system restarts it will be able to quickly verify the integrity of the volume by “replaying” the journal.
- The four erase options in Disk Utility are Don’t Erase Data, which simply replaces the volume’s directory structure; Zero Out Data, which provides good security by writing zeros on top of all the previous drive data; 7-Pass Erase, which provides even better security by writing seven separate passes of random information on top of all the previous drive data; and 35-Pass Erase, which provides the best security by writing 35 separate passes of random information on top of all the previous drive data.
- The Finder’s Secure Empty Trash will perform a 7-pass erase on the contents of the Trash folder.
- The three methods used to eject a volume or drive from the Finder are press and hold the Eject key for a few moments to unmount and eject optical media; select the volume you wish to unmount and eject from the Finder and choose File > Eject from the menu bar; and finally, in the Finder’s sidebar, click the small eject button next to the volume you wish to unmount and eject.
- Improperly unmounting or ejecting a drive or volume may cause data corruption. The system will automatically verify and repair an improperly unmounted or ejected volume the next time it becomes available to the Mac.
- RAID 0 uses disk striping to simultaneously write data to all drives providing increased performance but increases your chances of data loss due to drive failure. RAID 1 uses disk mirroring to write the same data to multiple drives, which does not increase performance, but it does greatly decrease your chances of data loss due to drive failure.
- There are two methods for using a burn folder in the Finder. First, you can create a burn folder of any size by choosing File > New Burn Folder from the menu bar. Once you are done adding and arranging items in the burn folder, click the Burn button and then insert a blank recordable optical disc. Or you can create a burn folder of a specific optical disc size by first inserting a blank recordable optical disc; then the Finder will automatically create a burn folder that matches the size of the recordable optical disc.
- Disk Utility can burn the contents of a disk image to an optical disk. Click the Burn button in Disk Utility’s toolbar, select a disk image, and then insert a blank recordable optical disc.
- The root level of a user’s home folder is visible to other users so they can navigate to the Public and Sites shared folders.
- The Shared folder is set up to allow all users to read and write files, but only the user who owns an item can delete it from the Shared folder. This is accomplished using the sticky bit permissions setting.
- Every home folder contains a Public folder that other users can read and a Drop Box folder that other users can write to. All other subfolders in a user’s home folder (except the Sites folder) have default permissions that do not allow access to other users. The Shared folder is also set for all users to share items.
- You can choose to ignore ownership on any nonsystem volume. This will ignore any ownership rules and grant any logged-on user unlimited access to the contents of the volume. This is a potential security risk because it will allow any local user account to have full access to the volume even if that user did not originally mount the volume.
- An item’s ownership and permissions can be identified using the Get Info or Inspector windows in the Finder, or by using the ls –l command in the Terminal.
- The Finder shows only four different permissions options: no access, read and write, read only, and write only. On the other hand, using the options available from the ls command in the Terminal will show you every possible permissions configuration.
- The sticky bit is a special permission used to define a folder as an append-only destination or, more accurately, a folder in which only the owner of the item can move, rename, or delete the item.
- The Disk Utility’s Verify and Repair feature is used to verify or repair the directory structure of a volume. The directory structure contains all the information used to locate files and folders on the volume.
- Target disk mode is a Mac-specific hardware feature that, when engaged, will share the Mac’s internal disk drives through the FireWire ports. Target disk mode can be engaged from the Startup Disk preferences or by holding down the T key as you turn on the Mac.