Boot Environment Variables - Cisco 7401ASR Installation And Configuration Manual

Boot Environment Variables

Boot Environment Variables
The contents of the boot environment variables, which are stored in the configuration file in NVRAM,
determine the actions your system takes on bootup. To see the current settings of these variables, use the
show bootvar command as follows:
Router> show bootvar
BOOT variable =
CONFIG_FILE variable =
Current CONFIG_FILE variable =
BOOTLDR variable does not exist
Configuration register is 0x100
Following are explanations for each of these boot environment variables:
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Cisco 7401ASR Installation and Configuration Guide
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BOOT variable—Points to the Cisco IOS software image that you want to boot; you set it in
configuration mode. The default software image is the CISCOxxx image (where xxx is a filename
assigned by the system, if you do not enter a specific filename). The system then looks for the first
image on the CompactFlash Disk in slot 0.
Enter configuration mode and specify a filename and CompactFlash Disk slot from which to boot
using the configure terminal and boot system commands as follows:
Router# configure terminal
Enter configuration commands, one per line. End with CTRL-Z.
System(config)# boot system flash disk0:rsp-p-mz.12-0
The result of this configuration file entry is that the BOOT variable is disk0: c7400-js-m...bin
CONFIG_FILE (configuration file) variable—Determines where the configuration is read from on
bootup; you set it in configuration mode as follows:
Router# configure terminal
Enter configuration commands, one per line. End with CTRL-Z.
System(config)# boot config disk0:configfile
The result of this configuration file entry is that the CONFIG_FILE variable is disk0:configfile.
BOOTLDR (boot loader) variable—Determines which image is used as the boot helper (boot
image); you set it in configuration mode as follows:
Router# configure terminal
Enter configuration commands, one per line. End with CTRL-Z.
System(config)# boot bootldr bootflash:c7401-boot-mz
The result of this configuration file entry is that the BOOTLDR variable is
bootflash:c7401-boot-mz.
Configuration register variable—Instructs the system where to look for a bootable Cisco IOS
software image; you set it as a hexadecimal value in configuration mode as follows:
Router# configure terminal
Enter configuration commands, one per line. End with CTRL-Z.
System(config)# config-register 0x102
The result of this configuration file entry is that the configuration register is set to hexadecimal
0x102. Please seeChapter 3, "Starting and Configuring," page 3-9, for more information about the
configuration register.
Appendix C Using the CompactFlash Disk
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