Debugging Commands; Configuration Register Commands - Cisco 2620 Configuration Manual

Appendix C Using the ROM Monitor

Debugging Commands

Most debugging commands are functional only when Cisco IOS software has crashed or is aborted. If
you enter a debugging command and Cisco IOS crash information is not available, the following error
message appears:
"xxx: kernel context state is invalid, can not proceed."
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Configuration Register Commands

The virtual configuration register resides in NVRAM. You can display or modify the virtual
configuration register from either the ROM monitor or the operating system software.
To change the virtual configuration register from the ROM monitor, enter the confreg command by itself
for menu mode, or enter the new value of the register in hexadecimal.
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Note
Entering confreg without an argument displays the contents of the virtual configuration register and
prompts you to alter the contents by describing the meaning of each bit. In either case, the new virtual
configuration register value is written into NVRAM, but is not effective until you reset or power-cycle
the router.
The following display shows an example of the confreg command:
OL-1957-04
–
upgrade rom-monitor preference<readonly|upgrade>—Selects the version of ROMMON to
be loaded the next time the router is reloaded. This command is used in the Cisco IOS exec
mode.
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rommon-pref—Used in ROMMON command mode. Provides the same information as
upgrade rom-monitor preference command in the Cisco IOS exec mode.
stack or k—Produces a stack trace.
context—Displasy processor context.
frame—Displays an individual stack frame.
sysret—Displays return information from the last booted system image. This information includes
the reason for terminating the image, a stack dump of up to eight frames, and, if an exception is
involved, the address where the exception occurred. For example:
rommon 8 > sysret
System Return Info:
count: 19, reason: a SegV exception
pc:0x802b1040, error address: 0x802b1040
Stack Trace:
FP: 0x80908398, PC: 0x802b102c
FP: 0x809083b0, PC: 0x802b0b88
FP: 0x809083d8, PC: 0x8017039c
FP: 0x809083e8, PC: 0x8016f764
confreg [hexnum]—Changes the virtual configuration register to the value specified. The value is
always interpreted as hexadecimal.
rommon 7 > confreg
Configuration Summary
enabled are:
Software Configuration Guide for Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers
Entering the ROM Monitor Mode
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