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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-06
Chapter 3 Assigning the Switch IP Address and Default Gateway
Modifying the Startup Configuration
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.
Note For complete syntax and usage information for the boot loader commands and environment variables,
see the command reference for this release.
Table 3-4 describes the function of the most common environment variables.
Tab le 3-4 Environment Variables
Variable Boot Loader Command Cisco IOS Global Configuration Command
BOOT set BOOT filesystem:/file-url ...
A semicolon-separated list of executable files to
try to load and execute when automatically
booting. If the BOOT environment variable is not
set, the system attempts to load and execute the
first executable image it can find by using a
recursive, depth-first search through the flash file
system. If the BOOT variable is set but the
specified images cannot be loaded, the system
attempts to boot the first bootable file that it can
find in the flash file system.
boot system filesystem:/file-url ...
Specifies the Cisco IOS image to load during the
next boot cycle. This command changes the
setting of the BOOT environment variable.
MANUAL_BOOT set MANUAL_BOOT yes
Decides whether the switch automatically or
manually boots.
Valid values are 1, yes, 0, and no. If it is set to no
or 0, the boot loader attempts to automatically
boot the system. If it is set to anything else, you
must manually boot the switch from the boot
loader mode.
boot manual
Enables manually booting the switch during the
next boot cycle and changes the setting of the
MANUAL_BOOT environment variable.
The next time you reboot the system, the switch is
in boot loader mode. To boot the system, use the
boot flash:filesystem:/file-url boot loader
command, and specify the name of the bootable
image.
CONFIG_FILE set CONFIG_FILE flash:/file-url
Changes the filename that Cisco IOS uses to read
and write a nonvolatile copy of the system
configuration.
boot config-file flash:/file-url
Specifies the filename that Cisco IOS uses to read
and write a nonvolatile copy of the system
configuration. This command changes the
CONFIG_FILE environment variable.