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Catalyst2950 and Catalyst2955 Switch Software Configuration Guide
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Chapter5 Assigning the Switch IP Address and Default Gateway Modifying the Startup Configuration
Environment variables store two kinds of data:
•Data that controls code, which does not read the Cisco IOS configuration file. For exam ple, 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 stor ed a s an e nvironment variabl e.
You can change the settings of the environment variables by accessing the boot loader or by using Cisco
IOS commands. 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,
refer to the command reference for this release.
Table 5 -5 describes the function of the most common environment variables.
Table5-5 Environment Variables
Variable Boot Loader Command Cisco IOS Global Configuration Command
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.
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 software image to load during
the next boot cycle. This command changes
the setting of the BOOT environment
variable.