Cisco CSR 1000v Series

CHAPTER 13
Accessing and Using GRUB Mode
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About GRUB Mode and the Configuration Register, page 221
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Accessing GRUB Mode, page 223
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Using the GRUB Menu, page 223
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Modifying the Configuration Register (confreg), page 224
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Changing the Configuration Register Settings, page 226
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Displaying the Configuration Register Settings, page 227
About GRUB Mode and the Configuration Register
The Cisco CSR 1000v has a 16-bit configuration register in NVRAM. Each bit has value 1 (on or set) or value
0 (off or clear), and each bit setting affects the router behavior upon the next reload power cycle. The Cisco
CSR 1000v GRUB mode supports a subset of configuration register options compared to ROMMON options
on other Cisco routers.
You can use the configuration register to:
•
Force the router to boot into the GRUB (bootstrap program)
•
Select a boot source and default boot filename
•
Recover a lost password
The table below describes the configuration register bits.
Cisco CSR 1000v Series Cloud Services Router Software Configuration Guide
221