Controlling Environment Variables - Cisco Catalyst 3750-E Software Configuration Manual

Chapter 3 Assigning the Switch IP Address and Default Gateway
Command
Step 3
boot system switch {number | all}
Step 4 end
Step 5
show boot
Step 6
copy running-config startup-config
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 b/s. 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:
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•
OL-21521-01
Purpose
(Optional) For switches in a stack, specify the switch members on which
the system image is loaded during the next boot cycle:
•
•
If you enter on a Catalyst 3750-X stack master or member, you can only
specify the switch image for other Catalyst 3750-X stack members.
If you enter on a Catalyst 3750-E 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.
Return to privileged EXEC mode.
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.
(Optional) Save your entries in the configuration file.
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.
Use number to specify a stack member. (Specify only one stack
member.)
Use all to specify all stack members.
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
Modifying the Startup Configuration
3-21