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Mac OS Directory FAQ
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This FAQ has been written as it is a
frequently answered question how to repair your
disk directory.
* Special note for Disk Warrior users at bottom
of FAQ *
Important exception notes many people forget:
1. You MUST backup your
data prior to repairing anything. Issues
which require software based repair frequently
appear to have the same symptoms as a dying hard
drive.
2. You can't repair the directory (Repair Disk
function of Disk Utility) of the current boot
drive. You must boot off a CD, or connect the
drive via target
disk mode that you wish to repair the
directory of.
3. You can't repair permissions while booted from
CD, except in Mac OS X 10.4 or later.
Given those exceptions visit these sections to
find the type of repair you need to perform:
4. A dying hard drive and a damaged directory can
have identical symptoms. As such, not having a
backup would leave you in a catch-22 situation if
both the directory and the hard drive are in bad
shape, leaving you only with a data recovery firm
(see my aforementioned backup your data link for
more info on data recovery). Prosoft Data
Rescue with an external Firewire hard drive
of greater size can recover information from a
dying hard drive as long as the directory is in
good shape. Disk
Warrior and Disk Utility (Repair Disk and
its cousin fsck) can repair a directory of a
healthy hard drive. Norton Utilities Speed Disk
and Disk Doctor starting with Mac OS 8.1 and later
has had a Russian Roulette possibility of damaging
the directory, and even more so with Mac OS X.
5. The release of Mac OS X 10.5 (Leopard) has
rendered all but Apple's Disk Utility and the
hardware test volumes that shipped with the Mac
(not that shipped with AppleCare) as safe to
repair the hard. That means Disk Warrior, Techtool
Pro are all awaiting Leopard compatible updates,
and as of the last writing of this FAQ on October
26, 2007, they are not.<
6. For all Macs
July 22, 2011 and later (use the serial number
to identify the age), Apple has documented
repairing the directory with recovery.
10.3 and above have
built-in Defragmentation
A very good series of discussions on Ars
Technica discuss defragmentation on 10.3 and
above. Coming from Windows and Mac OS 9, you may
have been used to running Speed Disk or another
defragmentation program. If you are defragmenting
to have room for very large files, it is
recommended to partition your hard disk so
you have a second partition that is used as a
scratch partition to store large files while you
work with them instead of using a separate
defragmentation utility. Then when you are done
editing, that partition can be erased without
touching the boot partition while running the boot
partition. Partitioning though does require
backing up your data, and if done with Disk
Utility, requires erasing the hard disk. See my backup FAQ for more
details on backing up. In addition, Apple has a
good discussion about what is defragmented on its
Knowledgebase
Article 25668.
Special note for
10.3 users
With Mac OS X 10.3 repairing your
directory is a little hairy since symptoms of a
bad directory may be indicative of having been
bitten by the firewire
bug if the problem is with an external
hard drive being invisible. If your external
hard drive becomes invisible after leaving it
mounted on your desktop during a restart,
shutdown, or an unsuccessful wake from sleep
forcing a restart, or a kernel panic
forcing a restart, you should assume that the
firewire bug has bitten you, and you should not
run any disk utility repair programs, and
instead get a compatible hard disk case or
firmware for your existing case as is mentioned
in the firewire bug
link. If you need to recover data,
information about that is in the link.
When to run Disk Utility
When to repair the disk directory, and
what is the disk directory -
First off, you should not run a directory repair
on a system that isn't backed up, unless you
have no choice. To learn more about backing up,
see this FAQ on backing
up. Note, you can sometimes recover your
data with Prosoft
Engineering's Data Rescue when no
directory repair utility works. However, this is
not something you should rely on, since outside
of that, and having no backup, data recovery
firms cost thousands of U.S. dollars. The most
important thing is to backup first, before
attempting to repair the directory.
The disk directory should be repaired anytime
you are forced to shut down or restart the
computer using the power switch instead of the
Apple menu (the Apple menu is the one with the
Apple logo in the far left corner of the top
white or gray bar of the screen).
If an application suddenly stops responding,
your first response may be to improperly restart
the computer. Don't! This will cause the
directory a certain amount of damage since
shutting down the computer properly involves
cleaning up many system items. You can hit the
command-option-escape key sequence (where
command is the key with the Apple logo and
cloverleaf logos on the keyboard), on an Apple
keyboard to force quit the offending application
that has hung. It will not save data that
program has worked on once it is force quit, but
will give you the chance to properly shut down
the computer.
Also if your hard disk is more than 85% full,
you should clean up
the hard drive of unneeded files. Having
an overflowing hard drive can cause the
directory to get corrupted. These can be any
files in your Home directory that you have
stored yourself. Do not touch content in any
other folders in Mac OS X other that folders you
create in your own Home directory without
consulting a technician first. Most of the iApps
let you delete unnecessary files directly from
the programs themselves, and they store files in
Home folder's Pictures, Movies, Music, and
Documents folder by default. The Library folder
is for Mac OS X use only, though bookmark and
mail stored documents frequently find themselves
either there or in the Documents folder. You can
delete no longer used applications in the
Applications folder if they are third party. Any
Apple applications should be left alone. Custom
create your own folder in the Finder by using
the File menu's New Folder command to save any
documents you want to open with word processors,
spreadsheets, or databases. If you do not follow
Mac OS X's file structure, it will make it more
difficult in the future to clean up files should
you find your hard disk is overflowing with
data, and make it more difficult to overcome a
directory failure.
In event of a kernel
panic you will not have a chance to force
quit anything, and a directory may get damaged
upon restarting the computer, or may already be
damaged.
The directory will be damaged significantly if
you get a circle with a slash through it at
startup and the computer stalls and won't budge
for several minutes. It can also be damaged if
you get a flashing ? over a floppy disk icon
during startup and that won't budge for several
minutes. Either will indicate that the computer
can not find your operating system folder or
programs, and is frequently indicative of a bad
directory, or a bad disk, or a bad connection to
the disk. When you get those responses from the
system, that's when to attempt to repair the
directory.
Note, Norton Disk Doctor and Norton Speed Disk
have at random caused disk directories to go
bad, and should not be run on any computer that
does not have any backup.
Directory repair should only be done to avoid
having to spend more time on recovering from
backup, but should never be done in lieux of
having a backup. Though on rare occasions a
directory may be so damaged as to require as
much as two weeks to repair. One such case was
reported on Apple Discussions board, and the
user was using Alsoft Disk Warrior (use version
3.0.3 for Mac OS X 10.4, known as Tiger. Intel
Macs can now use Disk Warrior 4.0). The
directory is the card catalog that tells the
computer where to find files on the computer.
You will see its damage when directory repair
programs report bad btrees, bad master directory
block, bad nodes. Some programs like Disk
Utility may not even see the hard disk when the
directory is damaged on the hard disk.
Note: Disk Utility may not detect all
directory malfunctions, and may incorrectly
determine the hard disk is OK, when in fact
there are errors only Disk Warrior can fix. If
you expect one of the above issues may have
caused damage to your directory run Disk
Warrior to be certain it has not after making
sure you are backed up!
How to repair the
directory with Disk Utility
Assuming you are not responding to the
firewire bug of 10.3,
repairing the directory is a simple process.
Insert your most recent Mac OS X bootable
installer CD and boot off it by starting your
Mac holding down the C key.
In some cases holding down the Option key is
necessary (instead of the 'C' key) to bring up
the CD on a menu you can click the disk icon on
the Startup Manager (Intel
version, PowerPC
version). In Macs that came with 10.7 or
later, booting from the recovery disk partition with
Command-R and selecting Disk Utility from the on
screen menu is required.
The Option key boot is only available on Macs
with built-in USB. When using the installer or
restore CD that comes with some computers, you
will be greeted with the Mac OS X installer and
the HD test volume using the Startup Manager.
Choose the Mac OS X Install volume on Software
Install and Restore disks that come with the
same computer, otherwise just choose the Mac OS
X install volume if installing from the retail
version of Mac OS X. Note you can't run the
installer of an older operating system on a
machine that came with a newer
PowerPC or Intel.
Select the right pointing arrow on the screen
after selecting the volume in the Startup
Manager to launch the installer.
Once your installer program comes on screen, on
the upper left corner of the white bar of the
screen a boldfaced menu called Installer will
become available (in Mac OS X 10.4 the menuitem
for Disk Utility has moved to the Utilities
menu). Click on that boldfaced menu, and select
Disk Utility. Upon entering disk utility, select
the hard disk whose directory you want to
repair, and click on the First Aid section of
Disk Utility. Click then on Repair Disk. In Mac
OS X 10.2 and later installers a Repair
Permissions is available, and should not be
selected unless you have the same version of Mac
OS X installed on the hard drive you are
repairing as is on the CD. If the CD was a Mac
OS X 10.2 installer, it is not the same as
having Mac OS X 10.2.3 installed on the
computer. Repair Permissions can be run if the
disk directory is OK and the computer otherwise
won't boot, but you should repair permissions
from the Disk Utility found in the Applications
-> Utilities folder and not the CD whenever
possible.* The
Repair Disk button is the only one that impacts
the disk directory itself. If after an attempted
repair it can't give you a result that "The disk
appears to be OK", then you should look at
either third party disk repair utilities, or
erasing your hard disk and recovering from
backup. This is one of the primary reasons it is important to have
backup. Two known good backup programs. A
well known disk directory repair program for Mac
OS X is Alsoft
Disk Warrior. Disk Warrior 3.0.3 is the an
upgrade that is a must for people using Mac OS X
10.4 (Tiger) with Disk Warrior, and version 4.0
makes it possible to repair the directory on
Intel Macs. This process on July 22,
2011 and later Macs (use serial number to
identify a Mac's age) is documented on Apple's support
article.
Special note
about repairing permissions
* Repairing permissions is not a
directory repair function. However, under
certain circumstances it becomes necessary to
repair permissions. Mac OS 9 programs are not
familiar with the permissions system of Mac OS
X, and if the directory is doing well, system
functions may not work properly or slow down
only because the permissions have gone astray.
In addition, anytime you install new software
which requires your password, it is possible
that the permissions of the system may not be
properly kept. As a result it is recommended you
repair permissions from Applications ->
Utilities -> Disk Utility -> First Aid
-> select hard disk on Mac OS X 10.2 or
higher whenever finished using Mac OS 9
applications and before and after installing new
software.
If you ran repair permissions and were
interrupted by a reboot or power outage, you'll
need to boot the Mac with an Apple USB keyboard
holding command and S keys together. At the
prompt type:
diskutil repairPermissions /
If that doesn't work, then look at the other
section of repairing the
directory with fsck.
For Mac OS X 10.1 users, upgrading to 10.1.5
will give you the ability to run Apple's repair
privileges utility which functions the
same as Mac OS X 10.2 and above's Disk Utility
-> First Aid -> repair permissions.
Note: Mac OS X 10.11, introduced September 30,
2015 has gotten rid of Repair permissions and
incorporated it in all official Apple updates
that need it.
The fsck command which
you have probably heard about on various
discussions board is the same command Apple
calls from the Disk Utility when you click
Repair Disk on a Mac OS X installer CD's Disk
Utility. The difference is that fsck can be
run when you don't have a Mac OS X installer
CD available to run Disk Utility. If the
machine is running Mac OS X 10.3 or higher you
need to type /sbin/fsck -fy instead of
/sbin/fsck -y to attempt an actual repair. Mac
OS X 10.2.8 and earlier don't require this.
The one thing it can't do is repair the
directory around its own command. So while it
is a nice stopgap measure which may work when
you don't have an installer CD, you should
also attempt to run Repair Disk from the Disk
Utility if problems persist. To run fsck,
restart the computer holding command-S at
startup (where command is the Apple logo key
on your Apple keyboard. This shortcut will not
work on most third party keyboards, and may
not work on the Apple wireless keyboard). A
command line screen will appear with
instructions to run fsck, and instructions to
run mount afterwards. When done type exit
followed by a return key.
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