OS X Topics

Physical Disk Problems

File System Problems

• Repair Permissions

Bad File System?

• UFS
• HFS

HFS+ vs. UFS

Partitioning: an evolving topic

about: swap

Disk Drive Problems?

File System Problems

The OS X system routinely checks the local disks at system startup time and also OS X will check removable drives upon insertion. The system utilizes a UNIX command line utility to do this check and provides an easily accessible Graphical User Interface to it in the Disk Utility program (located in the Utilities folder under the OS X Applications folder. The Disk Utility program allows you to correctly verify that local disks have no problems with the Verify option. If problems are indicated, you should then select the Repair option. Disk Utility will not allow you to repair the disk partition from which the OS X system is booted. If there are any problems with the boot partition they will be repaired when the system is rebooted. IF and ONLY IF there is something which the disk utility cannot repair by itself at system boot time on the boot partition, the system will not come up as usual, but instead will stop at a command line and instruct you what to do.

* * * A word of warning * * *

There are some who believe in the liberal use of the UNIX command line utility 'fsck', which checks and repairs file systems. This utility is meant to evaluate the state of a file system while it is NOT IN USE. [You may notice that prior to Disk Utility executing this command, the disk partition is unmounted.] When the system first boots, the boot partition is mounted READ-ONLY - and hence is inactive - this is when the boot partition is checked and repaired.

Utilizing the fsck command line utility on a file system that is mounted read-write and is active, will allow fsck to identify errors where there are none. IF fsck is allowed, or even forced to attempt to repair an operating file system, the file systems structures may be damaged beyond repair causing the loss of data.