Solved: Explain BOOTLDR variables to me

hfakoor222 · ‎03-19-2023

#sh bootvar | include not exist
BOOT variable does not exist
CONFIG_FILE variable does not exist
BOOTLDR variable does not exist
WARM_REBOOT variable does not exist

in normal production environments do all of these exist? Can someone give me a brief definition of each? Sorry to seem lazy, I've been reading Cisco docs, and my eyes hurt.

marce1000 · ‎03-19-2023

- It is advised to use and or check the meaning of these variables in the context of switch or router type you are using , because they may have different impact or meaning across platforms : so 'without warranty' :

 BOOT

variable points to the image for booting may not be needed , for instance when there is only one bin file , but that is platform dependend
When the

CONFIG_FILE

environment variable does not exist or is null (such as at first-time startup), the router uses NVRAM as the default startup device.
The

BOOTLDR

variable/file is the helper file to load the IOS. It specifies the Flash file system and filename that contains the boot loader image required to load system software.
The variable defines the primary Cisco IOS image that will load the final image from another source (on older systems) , nowadays it is no longer needed
I would presume that

WARM_REBOOT

allows users to reload their routers without reading images from storage. That is, the Cisco IOS image reboots without ROM monitor mode (ROMMON) intervention by restoring the read-write data from a previously saved copy in the RAM and by starting execution without either copying the image from flash to RAM or self-decompression of the image. Thus, the overall availability of your system improves because the time to reboot your router is significantly reduced.
But as stated , all of this may depend on platform type (too) and or behavior can differ,

M.

-- Each morning when I wake up and look into the mirror I always say ' Why am I so brilliant ? '
When the mirror will then always repond to me with ' The only thing that exceeds your brilliance is your beauty! '

View solution in original post

marce1000 · ‎03-19-2023

- It is advised to use and or check the meaning of these variables in the context of switch or router type you are using , because they may have different impact or meaning across platforms : so 'without warranty' :

 BOOT

variable points to the image for booting may not be needed , for instance when there is only one bin file , but that is platform dependend
When the

CONFIG_FILE

environment variable does not exist or is null (such as at first-time startup), the router uses NVRAM as the default startup device.
The

BOOTLDR

variable/file is the helper file to load the IOS. It specifies the Flash file system and filename that contains the boot loader image required to load system software.
The variable defines the primary Cisco IOS image that will load the final image from another source (on older systems) , nowadays it is no longer needed
I would presume that

WARM_REBOOT

allows users to reload their routers without reading images from storage. That is, the Cisco IOS image reboots without ROM monitor mode (ROMMON) intervention by restoring the read-write data from a previously saved copy in the RAM and by starting execution without either copying the image from flash to RAM or self-decompression of the image. Thus, the overall availability of your system improves because the time to reboot your router is significantly reduced.
But as stated , all of this may depend on platform type (too) and or behavior can differ,

M.

-- Each morning when I wake up and look into the mirror I always say ' Why am I so brilliant ? '
When the mirror will then always repond to me with ' The only thing that exceeds your brilliance is your beauty! '

hfakoor222 · ‎03-19-2023

thank you

Leo Laohoo · ‎03-19-2023

Eyes hurt from reading? Ok, I got pictures.

Look at the picture above. The most important part of the boot variable string are the two lines I have highlighted inside the yellow box. In Install Mode, the boot variable string must always point to the

packages.conf file

Manual Boot and Enable Break must always be "no".

Boot variable string is read during bootup, particularly while micro-code is being loaded. This instructs the switch, router, WLC to know what software to read (BIN or PKG files) and other stuff.