11-2
Cisco CSR 1000V Series Cloud Services Router Software Configuration Guide
OL-27477-07
Chapter11 Accessing and Using GRUB Mode
Accessing GRUB Mode
Table11-2 describes the boot field, which is the lowest four bits of the configuration register (bits 3, 2,
1, and 0). The boot field setting determines whether the router loads an operating system.
Note Use the 0x000 setting to configure the Cisco CSR 1000V to automatically enter GRUB mode when the
router boots.
Accessing GRUB Mode
Perform the following step to access GRUB mode:
SUMMARY STEPS
1. enable
2. config-register 0x0000
DETAILED STEPS
Table11-2 Boot Field Configuration Register Bit Descriptions
Boot Field
(Bits 3, 2, 1, and 0) Meaning
0000
(0x0)
At the next power cycle or reload, the router boots to the GRUB (bootstrap
program).
In GRUB mode, you must manually boot the system image or any other image by
using the boot command.
0001 - 1111
(0x01 - 0x0F)
At the next power cycle or reload, the router sequentially processes each boot
system command in global configuration mode that is stored in the configuration
file until the system boots successfully.
If no boot system commands are stored in the configuration file, or if executing
those commands is unsuccessful, then the router attempts to boot the first image
file in flash memory.
Command or Action Purpose
Step1 enable
Example:
Router> enable
Enables privileged EXEC mode.
•Enter your password if prompted.
Step2 config-register 0x0000
Example:
Router# config-register 0x0000
Enters the GRUB mode by entering the “0000” value
(0x0).