Directory
Damage or Computer Won't Boot
Repairing File Permissions
Non-Volatile Memory
Other Mac Tricks
Written
By: Adam Rosen
This article was published in the Adam's
Apple column on Low End
Mac
Directory Damage or Computer Won't Boot
The disk
directory is the table of contents for your hard drive. Directory errors
build up slowly over time, or quickly after a crash. Such errors can
cause problems opening or saving files, or if severe enough can prevent
your Mac from starting up, instead displaying the flashing question
mark. Fixing the disk directory and boot blocks often helps resolve
these kinds of problems.
DiskWarrior is my tool of choice to fix directory related problems.
You will need to restart your Macintosh from the DiskWarrior CD to fix
the internal hard drive. When DiskWarrior is ready, select your startup
drive and click Rebuild Directory. Replace your existing directory when
the process is complete, then restart normally to see if your problem
is fixed.
Other
disk utilities are worth trying
when DiskWarrior doesn't help. Apple's Disk Utility has a Repair Disk function that sometimes gets you going - you can restart
from your Mac OS X Install CD/DVD and run Disk Utility to fix your startup
drive. At a more sophisticated level TechTool Pro
and Drive
Genius let you test for various hardware damage and try to repair
errors; both also come on a bootable CDs or DVDs.
For Mac OS 9
and Classic users, Apple's Rebuild Desktop
routine can help fix problems opening files in Mac OS 9 applications.
For Classic Users running Mac OS X, use System Preferences --> Classic
--> Advanced tab to rebuild the desktop. If you're booted in Mac OS 9,
restart the Mac while holding down the Command (Apple) and Option keys
(CMD-OPT) simultaneously until you are
asked if you want to Rebuild the Desktop.
Repairing File Permissions
File
Permissions are security settings that permit or restrict access
to files and folders by different users. This security helps prevent
you from modifying special system files you shouldn't change, and prevents
other users from seeing the files inside your Home folder when you share
a machine. The easiest way to view or set a file's permissions is to
select the file (or folder) and choose Get Info in the Finder (File
--> Get Info, or CMD-I). The Ownership
& Permissions area shows who can do what with that file.
While
noble in intent, incorrectly set file permissions can sometimes prevent
you from launching applications or saving files. They can also cause
problems with OS updates. Apple is aware of this and so provides a way
to Repair Permissions that restores defaults and fixes many problems.
Use Apple's Disk Utility, select your boot drive, then
choose the First Aid tab (if necessary) and click Repair Permissions.
Let the process run completely.
TIP: Repair
Permissions before and after any System
Software updates for best results.
Non-Volatile Memory
The contents
of your computer's RAM are normally lost when you shut down, but some
settings are saved when the power is off: the date and time, your network
settings, choice of startup disk, etc.. These settings are stored in a special type of RAM
called Non-Volatile RAM (NV-RAM) or Parameter RAM (PRAM). A small battery
on the motherboard powers this special RAM when the computer is turned
off.
Sometimes
the PRAM gets corrupted, especially after a hard crash. Corrupt PRAM
can prevent your Mac from booting and causes all sorts of strange errors.
Resetting (or Zapping) the PRAM
can fix problems like these: restart your Mac .and after it chimes hold
down the Command (Apple), Option, P and R (CMD-OPT-P-R)
keys simultaneously. After a few seconds the system will restart again
and chime a second time. Now release keys the keys and boot normally.
Another
problem could be that the PRAM backup battery may be dead. This is typically
a 3.6V Li-ion battery which lasts about 5 years. If the date and time
on your computer are wrong each time you unplug Mac, then it's time
to replace the battery. The battery is accessible on most tower Macs,
otherwise a Mac service center can do this for you.
Other Mac Tricks
To
Eject a Stuck CD or DVD, especially with a slot loading drive, try this: restart your Mac and
hold down the mouse or trackpad button continuously until the disc ejects.
The works 90% of the time.
On
PowerPC-based Macs you can also Boot into Open Firmware
(which really impresses your friends and coworkers). Open Firmware is
Mac's BIOS and provides a few additional options for sick systems. Restart
your Mac and after the chime hold down the Command (Apple), Option,
O and F (CMD-OPT-O-F) keys simultaneously.
Eventually the system will boot to a white screen with ok> prompt.
You
can very thoroughly zap PRAM from this screen, even better than using
CMD-OPT-P-R; type the following lines:
-
ok> reset-nvram <RETURN>
- ok>
reset-all <RETURN> (system will then reboot)
You
can also use Open Firmware to eject CDs/DVDs that won't eject any other
way:
-
ok> eject cd <RETURN>
Sadly
the Intel-based Macs do not have Open Firmware, so equivalent tricks
are still waiting to be found!
Adam Rosen
