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CHAPTER 18 Disaster Recovery: BareMetal for SCO® Unix
18.1 Introduction
This implementation of the SCO Unix disaster recovery is BareMetal for SCO Unix, also known as the popular System Crash AIR-BAG, tailored for use with Backup Professional. The System Crash AIR-BAG allows you to restore your entire filesystem exactly as it was previously set up. All you need for this are the Air-Bag diskettes, the Master backup, and your last Incremental Tape Backup.
This documentation is for SCO Unix BP servers only! See "BareMetal Disaster Recovery: Intel® Platforms" on page 263 for information on SCO Unix BP clients.
You will find the Air-Bag diskettes to be of great reassurance. The knowledge that your data is secure even with a total system crash; and that even in the worst case, it can simply be transferred to another machine, is true security.
The Air-Bag diskettes can be used as utility diskettes by advanced users to salvage data from your hard disk in the event of a crash.
With this system you can do the following:
· Restore your entire filesystem to the same UNIX partition
· Enlarge your UNIX partition and restore your SCO UNIX filesystems to the original format
· Dial in through a modem to repair your crashed system
· And more...
18.2 Installing the System Crash AIR-BAG
The System Crash AIR-BAG is installed by extracting all the files from the installation diskette using xinstall (UNIX and OpenServer 5). Most often this occurs automatically with the installation of the backup product that comes with the Air-Bag. If you are installing an updated version, be careful that the Air-Bag is fully installed before generating your A1 and A2 diskettes. It is possible to have only installed the backup software portion of the upgrade, and invoke the Air-Bag from within the backup software menu system. However, if you are not careful, you may have invoked the old version since the upgraded files have not yet been installed. Therefore, if upgrading, be sure all products have been fully installed before invoking the Air-Bag diskette generator.
During installation your hard disk is checked for the presence of the 1024 Cylinder Barrier problem. If you are not running SCO OpenServer 5 (OS5), you can choose to save 250 blocks of space on your A2 diskette.
18.2.1 Creating Extra Space on the A2 Floppy
For UNIX 3.2v4 you can save 250 blocks of space on the A2 floppy by answering a few questions during installation and inserting the N2 floppy. The entire operation takes about 15 seconds and never needs to be done again. From that point on the A2 floppy has 250 more blocks of free space. Do this if you want to put additional utilities on the A2 floppy.
18.3 Creating the AIR-BAG Diskettes
18.3.1 Creation Script
The Air-Bag diskettes are created by using the script /etc/airbag. This script is loaded into the /etc directory during installation of the package. This script creates your A1 and A2 diskettes, from which you boot in an emergency to restore your system. You should be in multi-user mode when you create the A1 and A2 diskettes so that the system configuration under normal operating circumstances can be captured and then later restored when needed. The main creation menu appears as follows:
FIGURE 91. Airbag Creation Menu![]()
Each step of the creation of the Air-Bag diskettes is outlined in detail on the console screen. Most steps report a success or failure after completion of the step. At the end of all steps, this can be reviewed to check for error messages. Remember two important things when creating your diskettes. First, you should always make a spare copy of your A2 diskette. Second, you should always boot from the newly made A1 and A2 diskettes and test the tape and hard disk accessibility.
18.4 Testing the A1 and A2 Diskettes
If you are using the Air-Bag diskettes for the first time, you must always test the integrity of the A1 and A2 diskettes by booting from them and selecting the following choice from the Airbag Main Menu.
9) Verify Air-Bag Integrity (Test Tape and Hard Drive Accessibility)
This tests both the accessibility of the tape drive and the hard disk. Without this test there is no way you can be sure the A1 and A2 diskettes will work in the event of a system crash. It is tragic to have a system crash and find your tape drive is not working correctly when booted under the Air-Bag diskettes. This can be a serious problem because some third party vendor's tape products do not work properly with the tape when booted from a floppy disk.
It is a good idea before testing the tape drive to set the WRITE PROTECT TAB on the tape. On 4mm and 8mm tapes, this is a slot that covers a notch. The slot is moved so the notch is left opened. On 1/4 inch cartridge tapes, this is a circular cylinder that is turned 1/2 turn with a small flat screw driver. Turn the cylinder so the arrow points to the word "SAFE." If you do not want to verify the whole tape, but do want to make sure the drive is working, you can hit the <DEL> key while the tape is verifying. This takes you back to the Airbag Main Menu.
You should also test the Remote Modem Support Feature by testing the modem connectivity using the Airbag Utilities Menu.
If you have a floppy controller based tape drive and are not using OpenServer 5, you go through a three minute procedure of copying the Airbag Menu System to the free space on the hard disk. Don't worry. This does not overwrite any files on the hard disk. You then reboot to the hard disk based Airbag Menu System and proceed with testing the tape drive.
18.5 When to Regenerate AIR-BAG Diskettes
Anytime you reconfigure the tape (using "mkdev tape") and the kernel is rebuilt and relinked, you should regenerate the Air-Bag diskettes. If the SCSI ID of your tape drive is changed, you should regenerate the Air-Bag diskettes.
You need to regenerate the Air-Bag diskettes under the following circumstances:
1) You add a third party hard disk or tape driver
2) You change the sizes or number of filesystems
3) You change the mounting point of any filesystem
4) You add a DOS partition or any other partition
5) You add a bad track to the bad track table
6) You change anything using the divvy utility
7) After a restore when you selected NEW Hard Disk from the Airbag Menu System
*8) You add any new hardware card or change interrupts
*9) You relink the kernel and are not using /unix.airbag or /unix.N1
10) You change the SCSI ID of a tape drive or hard disk drive
* means optional, recommended but not required
18.6 The AIR-BAG Main Menu System
Air-Bag is designed to be used from a comprehensive menu system called the Airbag Menu System. From the Airbag Main Menu, there are two additional menus: they are the Airbag Utilities Menu and the Airbag UNIX Expert's Menu. To access the menu, boot your machine using the A1 and A2 floppies.
FIGURE 92. Airbag Main Menu System![]()
From the Airbag Main Menu you can immediately start the restoration of a UNIX system, either partially or entirely. There are four modes of restoration, as follows:
· Root Filesystem Only
· Fully Automated Restore to the Same Hard Disk
· Interactive Restore to the Same Hard Disk
· Interactive Restore to a New Hard Disk.
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