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Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 3 Configuring the Switch for the First Time
Modifying the Supervisor Engine Startup Configuration
When the boot field is set to either 00 or 01 (0-0-0-0 or 0-0-0-1), the system ignores any boot instructions
in the system configuration file and the following occurs:
• When the boot field is set to 00, you must boot up the operating system manually by entering the
boot command at the system bootstrap or ROMMON prompt.
• When the boot field is set to 01, the system boots the first image in the bootflash single in-line
memory module (SIMM).
• When the entire boot field equals a value between 0-0-1-0 and 1-1-1-1, the switch loads the system
image specified by boot system commands in the startup configuration file.
Caution If you set bootfield to a value between 0-0-1-0 and 1-1-1-1, you must specify a value in the boot system
command, else the switch cannot boot up and remains in ROMMON.
You can enter the boot command only or enter the command and include additional boot instructions,
such as the name of a file stored in flash memory, or a file that you specify for booting from a network
server. If you use the boot command without specifying a file or any other boot instructions, the system
boots from the default flash image (the first image in onboard flash memory). Otherwise, you can
instruct the system to boot up from a specific flash image (using the boot system flash filename
command).
You can also use the boot command to boot up images stored in the compact flash cards located in slot 0
on the supervisor engine.
Modifying the Boot Field
Modify the boot field from the software configuration register. To modify the software configuration
register boot field, perform this task:
To modify the configuration register while the switch is running Cisco IOS software, follow these steps:
Step 1 Enter the enable command and your password to enter privileged level, as follows:
Switch> enable
Password:
Switch#
Command Purpose
Step 1 Switch# show version Determines the current configuration register setting.
Step 2 Switch# configure terminal Enters configuration mode, and specify the terminal
option.
Step 3 Switch(config)# config-register value Modifies the existing configuration register setting to
reflect the way you want the switch to load a system
image.
Step 4 Switch(config)# end Exits configuration mode.
Step 5 Switch# reload Reboots the switch to make your changes take effect.