tboot -- Technical Information

Describe the tertiary bootstrap

Booting is the process of loading  COHERENT into memory and setting it into
motion.  This normally occurs after  you have turned on your computer.  The
term comes  from the old  expression about pulling  one's self up  by one's
bootstraps.

Booting can be  quite involved, and uses a number  of files, depending upon
the version  of COHERENT  being booted  and the medium  from which  you are
booting it.   The subject  of this article,  tboot, is the  booting program
that performs tertiary booting.

To  grasp what  is meant  by  ``tertiary booting'',  consider how  the boot
sequence works:

1. The BIOS loads  the first 512 bytes off of  the first hard disk and runs
   it.   This program  is called  the master  boot.  Mark  Williams Company
   recommends that  you use the  COHERENT master boot, because  it lets you
   boot off any partition on either of the first two drives.

2. The master boot  loads the first 512 bytes off  the active partition and
   runs that.  This program is the ``secondary boot'' program.

   The secondary  boot is generally  responsible for loading  the operating
   system off the active parition and running it.

Recent releases  of COHERENT need a more sophisticated  program to load the
operating  system  than can  fit  into  512 bytes.   In  these releases  of
COHERENT, the secondary boot loads a program off the root file system; this
program is called the ``tertiary boot'', or  tboot.

tboot  evaluates the  hardware of  your computer  to provide  the operating
system (COHERENT) with  vital information.  This evaluation allows COHERENT
to run without modification on a wider range of hardware.

tboot is  responsible for  loading the  operating system kernel.   It first
looks for  a file called autoboot,  which it then loads.   If autoboot does
not exist, tboot  prompts you to type in the  name of a kernel, e.g., begin
(during installation) or  coherent. If you do not remember  the name of the
kernel you wish to boot, you can type dir or ls for a list of files in your
root file system.

Pressing the  spacebar when the  prompt is displayed  prevents execution of
/autoboot and  causes tboot  to pause.   You can then  type the name  of an
alternate  kernel to  load  (assuming it  already resides  within the  root
directory), type ls  to see a listing of files,  or type info for a display
of hard-drive parameters.

See Also

Administering COHERENT,
booting

© 2012 by Stephen A. Ness