This section will detail step-by-step processes that can be used to fix some common booting and volume problems. It is not intended to cover every possible case. The purpose of the preceding sections was to give you the information that will allow you to figure out what might be going wrong.
For most hard disk users, it is not sufficient to merely have the device running. It is generally a good idea to make the system as robust as possible in order to avoid some of the problems that might cause a volume to become wholly unreadable. The ultimate fix is to reinitialize the volume from scratch and rebuild the volume with the Finder or a restore operation that uses the File Manager. This is guaranteed to fix anything except hardware problems, and will give you the most solid system. If your system is acting funny, you can try the following sequence that is the next best thing to initializing the disk. This sequence will not make you rebuild the disk, but can be fooled by some disk problems. If everything passes, then the disk is in good shape; maybe not perfect, but good.
1) Power down the entire system, including the hard disk that is suspect.
2) Run the HD SC Setup program (or equivalent) and Update the drivers on the
disk. For HD SC, this also fixes the parameter RAM. For non-Apple drives,
the parameter RAM can be reset with the Control Panel.
3) Run the Test Disk option in HD SC Setup (or equivalent). If the test fails,
reinitialize the volume, since it is not worth risking future problems.
4) Run the Disk First Aid utility. This utility will work on all HFS volumes.
Have it check the volume for consistency. If it reports any errors, you can
have it fix the problem, but the safest tack is to reinitialize. There are
some problems that Disk First Aid wonΓÇÖt catch. If Disk First Aid says the
volume cannot be verified, it is time to reinitialize.
5) Rebuild the Desktop file by holding down Option-Command when returning to
the Finder.
If you can successfully perform all of these steps, the volume will be as solid as it can get without reinitializing the disk. If things are still funny, it is time to take the last recourse, reinitialize.
Based on the previous sections, it is now time to go through all of the Nasties to give a step-by-step sequence for fixing these problems.
1) The data is intact, but the hard disk wonΓÇÖt boot.
This is for the case where the volume wonΓÇÖt boot, but if the computer is booted with a floppy disk the volume shows up at the desktop and can run normally. For this case, we know that the driver is being loaded and working, since the volume shows up at the desktop. The volume is also mountable, since it shows up with no problem. This implies that the Macintosh boot blocks are wrong, or the blessed folder is wrong. Clues such as the smiling Macintosh can tell you how far the process got before it failed. For example, if the smiling Macintosh never appeared, we know that Macintosh boot blocks were not read successfully. When the volume is fixed and bootable, it would be a good idea to go through the steps above to make the volume as solid as possible.
The sequence to follow:
a) Power down the entire computer, including the hard disk. Try to boot again.
If it works, you are done.
b) Use the Control PanelΓÇÖs Startup Device to set the hard disk as the Startup
Device. This will also reset some of the bytes in parameter RAM. Try
rebooting to see if it has fixed the problem.
c) Run HD SC Setup (or equivalent) and perform the Update Drivers procedure.
In the HD SC Setup case this will also rewrite the parameter RAM. If you
are not using HD SC Setup, blast the parameter RAM with the Control Panel.
Try rebooting.
d) Delete all System Folders from the hard disk. Using Find File or something
similar, be sure that there are no stray copies of the System or Finder
buried in some long lost folder. Copy a new System Folder to the volume,
using the Finder. This process will fix bad boot blocks, as well as a bad
blessed folder. Try rebooting.
e) If it still wonΓÇÖt boot, there is something very strange happening. Whenever
things get too weird it is usually time to start over: reinitialize.
2) The disk wonΓÇÖt boot and only shows up after running HD SC Setup.
The disk does not even show up at the Finder when the system is booted with a floppy. After running the HD SC Setup (or equivalent) the volume will appear on the desktop and be usable. The HD SC Setup and most similar utilities will do an explicit PBMountVol of the volume in order to make the volume usable. Since the volume does not show up at the Finder at first, this implies that the driver itself is not getting loaded or is working improperly, since there was no Disk Inserted Event for the Finder to use.
The sequence:
a) Power down completely, including the hard disk.
b) Run HD SC Setup (or equivalent) and Update the Drivers. For non-Apple
drives, update the drivers on the volume (this rewrites the SCSI partition
information as well) using the utility that came with the disk. Reset the
parameter RAM using the Control Panel.
c) If it still cannot be booted or does not show up at the Finder after
booting with a floppy, the volume is too weird and should be reinitialized.
3) The disk will boot but hangs part way through the boot process.
This is when you can see the volume is being accessed by the run light (LED) on the front panel, and the booting seems to work but never makes it to the Finder. This implies that all is well until the System tries to actually launch the Finder or Startup Application. It could also be that the System file is causing something to hang.
The sequence:
a) Power down completely.
b) Boot with a floppy so that the floppy is the startup disk and the volume in
question can be seen at the Finder.
c) Delete all System Folders on the hard disk. Put a new System Folder on the
disk. This will presumably fix a corrupted System file.
d) If still funky, show the disk whoΓÇÖs boss.
4) There are data errors while the disk is running.
This case usually evidences itself by messages at the Finder when trying to copy files. Messages like ΓÇ£The file ^0 could not be read and was skippedΓÇ¥ usually mean that the drive is passing back I/O errors. This usually means that there is a hardware failure, but it can occasionally be caused by bad sectors on the disk itself. If the sectors are actually bad, it is generally necessary to reinitialize the volume.
The sequence:
a) Power down completely. Reboot and see if the same file gives the same error.
b) Run the HD SC Setup (or utility that came with your drive) and perform the
Test operation. This will fail if there are bad blocks on the device. If
there are bad blocks, it is necessary to reinitialize the volume.
c) Check the SCSI terminators to be sure they are plugged in correctly. There
can be no more than two terminators on the bus. If you have more than one
SCSI drive you must have two terminators. If you only have one drive, use a
single terminator. If you have more than one drive, the two terminators
should be on opposite ends of the chain. The idea is to terminate both ends
of this wire that goes through all of the devices. If you have a Macintosh
II or SE with an internal drive, that drive will already have a terminator
inside the Macintosh at the front of the cable.
d) Make sure the SCSI cables you are using are OK, by swapping them with known
good ones. If the problem disappears, the cable is suspect.
e) Swap the terminators in use with known good ones to be sure they are OK.
f) Try the drive and cable on a different Macintosh to be sure the Macintosh
is OK.
5) The disk is very slow returning to the Finder.
If the computer has gotten slower with age, it is probably due to a problem with the Desktop file. If a volume has been used for a long time, the Desktop file can grow to be very large (Hundreds of K). Reading and using a file that big can slow down the Finder when it is drawing the desktop. If you have a large number of files in the root directory, this will also slow the computer down. A large number (500-1000) of files in a given folder can cause performance problems as well. If a volume has been used for a long time, it can also have become fragmented.
The sequence:
a) Rebuild the Desktop file and see if it gets faster.
b) Look for large numbers of files in a given directory and break them up into
other folders if needed.
c) Run Disk First Aid to be sure the volume is not damaged.
d) Reinitialize the volume and restore the data using File Manager calls to
fix a fragmentation problem. Using the Finder, or a backup program that
reads and writes files is a way to use only File Manager calls. You cannot
fix a fragmentation problem by doing an image backup and restore.
6) The computer crashes or hangs when returning to the Finder.
This can happen if the Desktop file becomes corrupted. There are occasions when this can happen if the HFS structures on the volume are damaged.
The sequence:
a) Rebuild the Desktop file.
b) Run Disk First Aid to be sure the volume is not damaged; a boot floppy with
the Set Startup set to Disk First Aid can allow you to test a volume that
cannot be displayed at the Finder.
c) The path of ultimate recourse if nothing else seems wrong with the volume.
7) The disk appears in a ΓÇ£This disk is badΓÇ¥ dialog.
This is the worst of the possible errors that generally happen to hard disks. If the message is ΓÇ£This disk is badΓÇ¥ or ΓÇ£This is not a Macintosh diskΓÇ¥, the HFS structures on the volume have been damaged. In particular, the Master Directory block on the volume has been damaged. The driver and SCSI partition information are probably OK, since this dialog shows up when the Finder tries to mount a damaged volume. This means that the PBMountVol call failed. DonΓÇÖt click the Initialize button unless you are sure you want the volume to be erased. In these cases, it is nearly always better to just reinitialize the volume after you have saved whatever information you can.
The sequence:
a) Power down completely. Occasionally the controller in the hard disk itself
can crash.
b) Run Disk First Aid. For these cases, it is usually necessary to create a
boot floppy with Set Startup set to Disk First Aid. When the floppy is
booted, Disk First Aid will be run before the Disk Inserted events are
processed. When Disk First Aid sees the Disk Inserted event it will check
the result from the PBMountVol and still allow you to test the volume, even
if it canΓÇÖt be mounted.
c) If Disk First Aid cannot repair the disk, it might be worth writing a
simple program to call the driver to read and write blocks. There is a copy
of the Master Directory Block on the end of the volume, and the volume can
sometimes be fixed by copying that block over a damaged block in sector 2.
You can write a program that will find out how big the volume is by looking
in the Drive Queue Element for the volume, reading the block that is one
sector from the end (N-1), and writing that copy over sector 2. At this
point, the volume is probably inconsistent, but it may allow you to use it
long enough to get information off of it. It is sometimes possible to have
Disk First Aid repair the volume at this point as well. Copying the sectors
can also be done with sector edit utilities, if you can get them to
recognize the volume at all.
d) If making a new copy of sector 2 does not work, but the driver is still
being loaded at boot time, it is possible to write a program that will read
sectors from the disk looking for information that you might need. You can
have a reader program go through blocks looking for a specific pattern,
like a known file name. This is usually done in desperation, but sometimes
there is no other choice. If the data desired can be found in some form, it
can sometimes be massaged back to a useful form much easier than recreating
it.
e) Sometimes the volume will be so badly damaged that the SCSI partition
information is also damaged and cannot be fixed with the Update in the hard
disk utility. In this case, it is usually still possible to perform direct
SCSI reads, without going through the driver. Using the driver is
preferable, since it knows how to talk to the drive better than you would,
but sometimes the driver is not available. Using direct SCSI reads should
be a last ditch effort since the SCSI Manager can be very challenging to
use. This should only be used if there is irreplaceable data on the volume
that cannot be read by any other means.
f) Even if the volume is recovered, it still should be reinitialized (after
the data is recovered) to be sure that any hidden damage is repaired.
8) The disk never shows up at all.
The disk appears to be missing. The volume does not show up at the Finder, and does not show up in HD SC Setup. At boot time the access light (LED) does not flash. This is usually a hardware problem as well. The drive is not responding to SCSI requests at all, so the system cannot tell a drive is attached.
The sequence:
a) Power down the system, including the hard disk.
b) Make sure that the SCSI ID on the drive does not conflict with any other in
the system, including the Macintosh, which is ID 7. (If you have an
internal hard drive, it should be ID 0.)
c) Check the SCSI terminators to be sure they are plugged in correctly. There
can be no more than two terminators on the bus. If you have more than one
SCSI drive you must have two terminators. If you only have one drive, you
should use a single terminator. If you have more than one drive, the two
terminators should be on opposite ends of the chain. The idea is to
terminate both ends of this wire that goes through all of the devices. If
you have a Macintosh II or SE with an internal drive, that drive will
already have one terminator inside the Macintosh at the front of the cable
d) Make sure the SCSI cables you are using are OK, by swapping them with known
good ones.
e) Swap the terminators in use with known good ones to be sure they are OK.
f) Try the drive and cable on a different Macintosh to be sure the Macintosh
is OK.
These boots are made for wokking
Remember, the goal here is to make the system be as stable as possible. If things are acting strange, it doesnΓÇÖt hurt to go through the entire process of testing the drive. The test procedure takes a little time but is non-destructive for the data that is there. If something catastrophic has happened to the disk, it is better to spend some time backing up the data, initializing the volume, and restoring the data than it is to lose some work later on due to some other permutation of the same problem. Unless you are sure that the volume is in an undamaged state, you are better off using a file-by-file backup operation than an image backup, since the image backup will copy any damage as well as the data.
If there are situations that you run into that are not covered by this technical note, please let us know so that they can added.
If this technical note helps even one person save some data that would otherwise be lost, it will have been worthwhile. Hope it helps.
