Cisco Systems 3750E manual Controlling Environment Variables, Boot system switch number all

Chapter 3 Assigning the Switch IP Address and Default Gateway

Modifying the Startup Configuration

	Command	Purpose
Step 3
	boot system switch {number all}	(Optional) For Catalyst 3750-E switches, specify the switch members on
		which the system image is loaded during the next boot cycle:
		• Use number to specify a stack member.
		• Use all to specify all stack members.
		If your Catalyst 3750-E switch is a stack master or member, you can only
		specify the switch image for other Catalyst 3750-E stack members.
		If you want to specify the image for a Catalyst 3750 switch, enter this
		command on the Catalyst 3750 stack member.
Step 4
	end	Return to privileged EXEC mode.
Step 5
	show boot	Verify your entries.
		The boot system global command changes the setting of the BOOT
		environment variable.
		During the next boot cycle, the switch attempts to automatically boot up the
		system using information in the BOOT environment variable.
Step 6
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

To return to the default setting, use the no boot system global configuration command.

Controlling Environment Variables

With a normally operating switch, you enter the boot loader mode only through a switch console connection configured for 9600 bps. Unplug the switch power cord, and press the switch Mode button while reconnecting the power cord. You can release the Mode button a second or two after the LED above port 1 turns off. Then the boot loader switch: prompt appears.

The switch boot loader software provides support for nonvolatile environment variables, which can be used to control how the boot loader, or any other software running on the system, behaves. Boot loader environment variables are similar to environment variables that can be set on UNIX or DOS systems.

Environment variables that have values are stored in flash memory outside of the flash file system.

Each line in these files contains an environment variable name and an equal sign followed by the value of the variable. A variable has no value if it is not listed in this file; it has a value if it is listed in the file even if the value is a null string. A variable that is set to a null string (for example, “ ”) is a variable with a value. Many environment variables are predefined and have default values.

Environment variables store two kinds of data:

•Data that controls code, which does not read the Cisco IOS configuration file. For example, the name of a boot loader helper file, which extends or patches the functionality of the boot loader can be stored as an environment variable.

•Data that controls code, which is responsible for reading the Cisco IOS configuration file. For example, the name of the Cisco IOS configuration file can be stored as an environment variable.

You can change the settings of the environment variables by accessing the boot loader or by using Cisco IOS commands. Under normal circumstances, it is not necessary to alter the setting of the environment variables.

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

OL-9775-02 3-15