You can procure the mini-root from the operating system vendor. The load script can be written from scratch or you can use the one in Listing 1.

Implementing the Procedure

The subsections that follow present detailed instructions for implementing the procedure.

1. Create the Master Software Configuration

Set up the Master with all system files, user files, and application software. Keep the files unique to each Slave generic, so that, using operator input, the load script can automatically change them to Slave-unique files during production.

For example, our machines have hostnames defined in the file /etc/rc.local, which means that this file is different on each Slave. In our case, the Master generic file /etc/rc.local would contain the following command:

/bin/hostname XXXXX

At production time, the load script will prompt the operator for the hostname of the Slave currently being loaded. The load script will then copy the generic file /etc/rc.local from the production tape to the Slave boot-disk. If the operator enters "GRUMPY" for the Slave name, the load script will then change the generic file into the Slave-unique file containing the command:

/bin/hostname GRUMPY

Each file on the Master that contains Slave-unique information should be made generic, and the load script should be written to change that file from generic to Slave-unique.

2. Place the Mini-Root on the Master Boot-Disk

Place the vendor distribution tape containing the mini-root in the Master tape drive. Then, from the Master, copy the mini-root from the tape to the directory /tmp by executing the command:

dd if=/dev/rmt0h of=/tmp/miniroot ibs=1024 obs=8192 conv=sync

See the sidebar "Device Issues" for details on the use of the dd(1) command with tapes.

This procedure copies every file from the Master to the production tape, including the mini-root. Because the mini-root is not used during normal operation, placing it in the directory /tmp ensures that it will be removed automatically on Slave boot-up.

3. Place the Load Script on the Master Boot-Disk

The load script performs the following functions on the Slave during production:

-- Partitions the boot-disk, using the chpt(8) command.

-- Writes the boot-blocks (usually supplied as part of the mini-root) to the boot-disk, using the dd(1) command.

-- Creates two filesystems on the boot-disk, using the mkfs(8) command.

-- Restores each filesystem dump from the production tape to the boot-disk, using the restore(8) command.

-- Performs Slave-specific editing of generic files using operator inputs and the sed(1) command.

-- Checks boot-disk filesystem integrity, using the fsck(8) command.

-- Shuts the mini-root down, using the sync(1) and halt(8) commands.

You can create a Bourne shell load script, to perform these functions, or you can use the one shown in Listing 1. Keep in mind that the commands in the mini-root are very few and very primitive (see the sidebar, "Required Mini-Root Functions"). The load script can also be written to interactively accept command arguments from the operator at production time.

In this particular example, the operator enters three command arguments (Slave hostname, IP address, and swap partition size); all the other arguments are predetermined and hard-coded into the load script.

When your load script is debugged, place it on the Master boot-disk in the file /tmp/loadscript.

4. Create the Production Tape from the Master

The mini-root, load script, and two filesystems dumps are written sequentially to the production tape by executing the following commands from a Bourne shell on the Master:

of="/dev/nrmt0h"
arg="ibs=8192 obs=1024 conv=sync"
mt rewind
dd if=/tmp/miniroot of=$of $arg
dd if=/tmp/loadscript of=$of $arg
dump 0usdf 21600 16000 $of /
dump 0usdf 21600 16000 $of /usr

Note the tape device driver (of) in the above commands is no-rewind (i.e., nrmt0h as opposed to rmt0h), so that files can be written sequentially. The mt(1) command ensures the tape is completely rewound and ready for writing. The dd(1) command sequentially writes the files /tmp/miniroot and /tmp/loadscript from the Master boot-disk to the production tape. The dump(8) commands sequentially write level 0 dumps of the Master filesystems / and /usr to the production tape. (See the sidebar "Device Issues" for details on the use of the dd(1) and dump(8) commands with tapes.)

This completes the creation of the production tape.

5. Create Multiple Copies of the Production Tape

Copies of the production tape can be made either by repeating steps 1 through 4 above or by making tape-to-tape copies. The procedure for tape-to-tape copies is straightforward:

a) Set up the Master with the additional tape drive.

b) Place the source tape in the default drive (e.g., rmt0h).

c) Place the destination tape in the second drive (e.g. rmt1h).

d) Copy the mini-root and load script from the source tape to the destination tape by executing the following commands from a Bourne shell on the Master:

s="/dev/nrmt0h"
d="/dev/nrmt1h"
mt rewind
mt -f $d rewind
dd if=$s of=$d bs=1024
dd if=$s of=$d bs=1024

e) Copy the filesystem dumps from the source tape to the destination tape by executing the following commands from a Bourne shell on the Master:

dd if=$s of=$d bs=10240
dd if=$s of=$d bs=10240

Note the tape device drivers (in the variables s and d) in the above commands are no-rewind. The filesystem dumps must be written with a block size of 10240 bytes, as this is the size the dump(8) command uses to create the dump files, and the size the restore(8) command uses when restoring them.

7. Create Slaves from the Production Tape

Once the production tapes have been made, creating Slaves is quick and easy. From each Slave, perform the following steps:

a) Place the Slave in console (maintenance) mode (some machines can be placed in console mode with the operating system command shutdown -h now; others may require some other command or cycling power).

b) Put the production tape into the Slave tape drive.

c) At the Slave console mode prompt, boot the mini-root from the production tape by executing the following console command:

boot 3/tz5/vmunix

(This is a DEC 5000/240 console command to boot the mini-root from the tape drive at SCSI ID#5; consult your machine's maintenance documentation for details about your system.)

d) Once in the mini-root Bourne shell, set your preferred erase keystroke by entering the mini-root command:

stty erase '^?'

Note: some mini-roots may boot into a utility menu. If this is the case, choose an option from that menu that will place you in a mini-root Bourne shell.

e) Make the special files for the tape and boot-disk drives by entering the mini-root commands:

cd /dev
MAKEDEV tz5 rz0

f) Position the production tape at the load script by entering the mini-root command:

mt fsf 1

Forward-spacing the production tape one file (i.e., skipping past the mini-root to the load script) is necessary because booting the mini-root usually rewinds the tape.

g) Copy the load script from the production tape to the mini-root filesystem by entering the mini-root command:

dd if=/dev/nrmt0h of=/loadscript \
ibs=1024 obs=8192 conv=sync

Note the use of the no-rewind device.

h) Execute the load script by entering the mini-root command:

sh /loadscript

i) Answer any load script questions appropriately.

When the load script is finished executing, it will shut the machine down, at which point you can boot it into service!

This is the end of the procedure.

Summary

At HSSC, our system load for one boot-disk is about 354Mb on one 660Mb disk. Our serial-based method of copying the Master disk took about 30 minutes, so one operator could generate two Slaves per hour.

The parallel procedure presented here also takes about 30 minutes to create one Slave. But with five copies of the production tape, one operator can load five machines in parallel in about 30 minutes, which is about ten machines per hour, with practically no production hassles.

About the Author

Packey Velleca graduated from Floria Institute of Technology in Melbourne, FL with a BSEE in 1988 and is employed by Harris Space Systems Corp. He currently works with a group of administrators for a small system of real-time computers with UNIX-based operator workstations. He can be reached via email at pvelleca%core1@kssib.ksc.nasa.gov.