Silicon Graphics CHALLENGE L, User Manual, Page: 139 / 164

Environment Variables
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POD (Power On Diagnostics) Mode
In the unlikely event of an extreme hardware failure, the system may drop
down into a low-level diagnostic environment known as POD mode. This
mode is used as an aid to system diagnosis and is not intended for use by
customers. If your system enters POD mode, contact your service provider.
Environment Variables
This section describes procedures that you can use to customize certain
aspects of the PROM Command Monitor. Many aspects of the system
startup process can be individually tailored by changing the PROM
environment variables. These variables are changed using the
setenv
command while in the Command Monitor. Enter the Command Monitor by
first selecting the “Stop for System Maintenance” option during the system
startup. When the System Maintenance menu is displayed, enter the
Command Monitor by typing
5
.
Some common modifications are described in the following subsections.
Additional information is provided in the
prom(1M) reference (man) page.
Booting From an Alternate Device
There are three environment variables in the PROM that are used to specify
which device to boot from: the “SystemPartition,” the “OSLoadPartition,”
and the “root” variable.
The “SystemPartition” variable specifies the location of the device volume
header. Its default value is “dksc (0,1,8),” which specifies SCSI controller 0,
disk 1, and partition 8 (by convention, the volume header is always
partition 8).
The “OSLoadPartition” variable specifies the device from which the IRIX
kernel should be loaded. Its default value is “dksc (0,1,0),” which tells the
PROM to look for the kernel on SCSI controller 0, disk 1, on partition 0 (by
convention, the kernel location is always partition 0).