Apple has offered a wonderful tool for the Mac operating system i.e. disk-related tasks- disk utility. One more utility is there which checks the consistency of the file system. Both of them perform wonderful tasks and are able to address few of the startup issues in Mac.
These utilities can also be used for the entirely running systems, just to check the inconsistency problems with the disk and the file system, if any. There are few symptoms and error messages that make you feel that you need either of the utilities. Some file system errors may prevent the system from boot which can be the outcome of the unexpected system shutdown. Your computer starts but sometimes either it won't reach the login screen, or it may reach the login screen but not load the desktop after you log in. These are the cases when you need disk utility to get access to your valuable data.
Try to start the system in the safe mode. But if the problem persists then using disk repair is mandatory. The disk repair performs various tasks for verifying the disk integrity and repairing if the disk is damaged in few of the cases.
fsck is a command line utility which is recommended if the disk utility is not able to perform the task. These are the cases when you can’t start with the safe boot or the optical drive isn’t visible. fsck utility provides options for either interactively repairing damaged file systems ,automatically deciding how to fix specific problems, or reviewing the problems that need to be resolved on a file system without actually fixing them.
But sometimes both these utilities don’t act as the perfect answer for the complicated data inaccessibility problems. These may results in the error messages like:
“overlapped extent allocation”
In some of the cases the incorrect application of the utility leads to the problems, needed to be addresses by another alternative, like running fsck on a mounted file system can potentially cause severe data corruption/loss.
To fix the problem of the data inaccessibly due to hard drive damage and file system related issues are termed as Mac recovery tools. If this is the case of some physical mischief with the hard drive, then you need to recover it from Mac recovery software.