Cisco WS-C4003 Software Guide - Page 421
Understanding the BOOT Environment Variable, Understanding the CONFIG_FILE Environment Variable
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Chapter 28 Modifying the Switch Boot Configuration Understanding How the Switch Boot Configuration Works The other bits in the configuration register function as follows when set: • Bit 5 (0x0020): Enables CONFIG_FILE recurrence. • Bit 6 (0x0040): Causes system software to clear NVRAM contents. • Bit 7 (0x0080): Enables OEM bit (not used). • Bit 8 (0x0100): Disables break. • Bit 9 (0x0200): Uses secondary bootstrap (not used by the ROM monitor). • Bit 10 (0x0400): Provides IP broadcast with all zeros (not used). • Bits 11/12 (0x0800/0x1000): These bits are always set to 0/0 (9600 baud). • Bit 13 (0x2000): Boots default Flash software if network boot fails (not used). • Bit 14 (0x4000): IP broadcasts do not have network numbers (not used). • Bit 15 (0x8000): Enables diagnostic messages and ignores NVRAM contents (not used). Understanding the BOOT Environment Variable The BOOT environment variable specifies a list of image files on various devices from which the switch can boot at startup. You can add several images to the BOOT environment variable to provide a fail-safe boot configuration. If the first file fails to boot the switch, subsequent images specified in the BOOT variable are tried until the switch boots or there are no additional images to attempt to boot. If there is no valid image to boot, the system enters ROM-monitor mode where you can manually specify an image to boot. The system stores and executes images in the order in which you added them to the BOOT variable. If you want to change the order in which images are tried at startup, you can either prepend and clear images from the BOOT variable to attain the desired order or you can clear the entire BOOT environment variable and then redefine the list in the desired order. Understanding the CONFIG_FILE Environment Variable In software release 5.2 and later, you can use the CONFIG_FILE environment variable to specify a list of configuration files on various devices to use to configure the switch at startup. You can specify one of the following functions: • Nonrecurring-When you add a list of configuration files to the CONFIG_FILE environment variable, the next time the switch is restarted, the system erases the configuration in NVRAM and uses the specified files to configure the switch. The CONFIG_FILE variable is cleared before the switch is configured. Nonrecurring is the default setting. • Recurring-When you add a list of configuration files to the CONFIG_FILE environment variable, the list is stored indefinitely in NVRAM. Each time the switch is restarted, the system erases the configuration in NVRAM and configures the switch using the configuration files specified. The CONFIG_FILE variable is not cleared. Note Remember that the CONFIG_FILE variable can be altered or its recurrence properties changed by commands in the configuration files used to configure the switch at startup. For information on specifying recurrence or nonrecurrence, see the "Setting CONFIG_FILE Recurrence" section on page 28-5. 78-12647-02 Software Configuration Guide-Catalyst 4000 Family, Catalyst 2948G, Catalyst 2980G, Releases 6.3 and 6.4 28-3