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Performing a "Clean System Install" - Source:

Performing a "Clean System Install"

Performing a "Clean System Install"
Crashed or frozen programs, buggy software, disk problems, and general system misbehavior can seriously affect the MacOS without leaving any obvious traces. The System file is kept open by the MacOS at all times. The same is true for the Finder, fonts, enablers, and some other system software. If there is a system problem, it is possible that these files may be damaged. Usually a damaged system file manfests itself quickly; the mac will refuse to boot, or crash during the startup process. It is possible, however, for certain resources within the system file to be corrupted without the entire system file being damged. This can lead to unexplained system crashes and freezes

If a Macintosh is crashing often, and the problem is not due to Extension/Control Panel conflicts, SCSI chain errors, damaged hard drive structure, damaged desktop files, or corrupted PRAM, the problem is probably with the MacOS software itself; it should be reinstalled. When Apple's System Software Installer is run, it examines the current operating system files and copies certain resources from the old System software to the new system software. Ordinarily; this would be a good thing; the software is updated without needing any configuration or setup. Unfortuneatly, if the resources that are copied are the resources causing the problems, the new software will not work any better than the previous system. A "Clean System Install" means installing a fresh System folder without any consideration for the current (and possibly damaged) system software. When trying to solve a problem, it is always a good idea to do a clean system install. If you are just updating your system software, a normal installation is all that is necessary.

Before System 7.5, it was necessary to trick the Apple Installer into creating a new System folder by preventing it from seeing the current system software. Simply renaming the current system folder and dragging the System File out of it before launching the Installer was enough; a new System folder would be created. The System 7.5 installer can do a clean install itself. After launching the installer and clicking "Ok" after the startup screen, press command-shift-k to bring up this dialogue box:

clean install

Select "Install New System Folder" and click "Ok" to let the Installer perform a clean install.

Starting from Scratch: Total Reinstall
The best and most impractical thing to do when performing a major System Software update or when fixing a crash-prone Macintosh is a "Total Reinstall". This procedure involves completely wiping the hard drive; if there is any important data on the drive, it will need to be backed up. A total Reinstall requires a Silverlining Boot Disk, the System 7.5 Disk Tools Disk, the WEB Boot Disk, the MacOS v7.5 install disks (or a network install server), the MacOS v7.5 Update v1.0 disks (or a network install server), the Network Software Install Disk v1.5.1, and a Norton Boot disk v3.1 or higher.

Free;spare Your Drive

1. Boot from the SilverLining disk and format your drive with the Silverlining driver (version 5.5). Use the default values for your drive. The drive icon is of no consequence.
2. Once the new partition structure is presented to you for updating simply select the size designation of the Apple Partition Map with the cursor. An additional check box will appear in the lower left of the main dialogue box you are in. Check it and say update. Ignore the message it will erase EVERYTHING (and it does mean everything) on your hard drive. This is exactly what you want it to do.
3. Quit SilverLining and prepare to shut down your Macintosh.
4. Once the drive is in a state of "free;spare", you may shut down your Macintosh and disconnect any network, serial, or SCSI device.
5. Restart your Macintosh without a boot floppy in order to reset the parameter RAM (pRAM). If you own a PowerBook, you need not do anything but use the keyboard sequence to do so. Desktop Macs require the removal of all NuBus and/or PDS-type cards before resetting the parameter RAM so as to clear a sub-register referred to as "slot" pRAM.

Keyboard Sequence for Resetting the Upper PRAM Register

1. Start up your Macintosh and quickly depress, simultaneously, the command-option keys, as well as the P and R keys (conveniently, for parameter and RAM). Make certain your caps lock key is not down or the pRAM will not reset. Keep holding these keys down all the while listening for the startup chime.
2. Without lifting your fingers from the keys, keep listening for the startup chime two more times. Once you have heard the sound three successive times you may consider the pRAM completely reset.

Reformatting Your Drive

1. Make sure your internal hard drive is at SCSI address "0" (some exceptions exist to this but they are rare).
2. If you have an OEM Apple drive, format the hard drive with the version of the SC HD Setup software provided on your Disk Tools or latest version found on ASHD1.
3. If you do not have an Apple drive, the ProSoft/APS Tools v3.07 formatting software should be used because of its superior ability to configure and install the SCSI driver with aspects important to 7.5 and PowerBooks (re: allow disconnect) running 7.5.x.

How do you know whether you have an Apple drive? Run the SC HD Setup software from your desktop. If it gives you the message that a "suitable drive cannot be found" it's not an Apple drive. If it comes up ready to initialize or update, then it is an Apple drive and you should use the software prescribed by Apple for their drives, the SC HD Setup software.

Install and Update

1. Insert your System 7.5 disk install #1 and proceed with your system install if you have the System 7.5 install disks. If you are installing from a server, boot with the WEB Boot Disk and mount the server install volume (ASHD server). Proceed with the installation.

If you are not setting up a maintenance or field drive which will be used on many models of Macintoshes, then be sure to select Custom Install and install only the system software for your Macintosh. Also, go down through the list of items to install and select exactly what you want to install (even though there are a few bugs in the installer, especially with the Apple Menu selections). A custom install is always safer since you are manually telling the installer what to do. Easy Install leaves the installer to automated code routines which are always more likely to cause problems. This is true of ANY type of software install on the Macintosh.

2. Once you have successfully installed 7.5, simply restart. Do not disable or trash any system file.
3. Restart with extensions off (shift key depressed on restart).

It is essential that you do not update with extensions or cdevs disabled via the extension manager. If you do, these extensions and cdevs will be skipped in the updating process and should you enable them again the future, they will cause myriad problems since you will be commiting one of the cardinal Macintosh sins by mixing varying versions of various components of an OS within the same OS folder on your Macintosh.

4. Insert your System 7.5.1 Update disk #1 and proceed with your system install if you have the update disks. If you are updating from a server, boot with the WEB Boot Disk and mount the server update volume (ASHD server). Proceed with the installation.
5. Once the updater has been run, Restart.

This restart must be with the Extensions ON in order to run the Installer Cleanup from the System 7.5 Updater.

6. Restart a second time with the Extensions off and install the NSI v1.5 disk from Apple.

This upgrades AppleTalk to v58.1.5 and EtherTalk to v2.5.7. Other updates and installs are available on this version of the NSI as well, including token ring and the new LaserWriter Bridge software (which allows for a postscript laserwriter to be connected via the LocalTalk port of a specific Macintosh and be "seen" by other computers on the EtherNet network the Macintosh is currently on; a sort of mini-internet router).

Final Preparations

1. Once you have completed these installs, restart twice more with the extensions ON, then off and rebuild the desktop using the command-option key sequence.
2. Once the rebuild is complete, run Norton's Utilties Disk Doctor 3.1 or higher to reset/fix the master alternate header block listing.
3. After successfully doing this, you may restart your Macintosh one final time and let it boot normally, complete with extensions and cdevs.

Reinstalling Applications and Data

1. Once the system has been installed, run the installers for all the applicaitons you would like on the drive. Use the original disks. If there are no installer programs, copy the application and files directly to the hard drive.
2. Copy the data files from the backup medium back to the hard drive

You are now through with your updating and should be ready to enjoy the increased speed and reliability of Mac OS v7.5.1.

If you have extra info about this page, if you noticed errors, please help me to maintain this site. Send me the information you have, I will update the page as soon as possible. Thank you in advance.


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