From: Jay Hennigan (jay@west.net)
Date: Mon Jul 07 2003 - 11:19:08 GMT-3
On Mon, 7 Jul 2003, Alec Pun wrote:
> Hi group,
>
> I am using IOS 12.0 in my Cisco 2501. Just curious why the flash is always
> read-only. I am not sure if this is the reason why I can not copy
> running-config to flash, say using another filename.
2500s run from flash. That is, the flash is used for the actual running
IOS kernel. Most other routers run from RAM where at boot, the image is
copied from flash into RAM and the kernel runs from RAM. Often the image
is decompressed as it's copied. 2500s don't do this in order to conserve
RAM.
Because the running IOS is in flash and being addressed real time, IOS
locks the flash to read-only mode to prevent corruption of the running
image.
For upgrading, you can change the config register to 0x2101 and boot
from boot ROM which will give you enough functionality to get IP
connectivity and a TFTP client to write a new image to flash.
Newer systems have a "flash helper mode" that automates this by remembering
your TFTP settings, rebooting into boot ROM mode, doing the flash erase,
TFTP transfer and write, then rebooting into normal mode. Not to be
done remotely by the faint-of-heart. :-)
So for storage of "extra" stuff like configs, consider offloading them
to a TFTP server somewhere else instead of local flash on 2500s.
-- Jay Hennigan - CCIE #7880 - Network Administration - jay@west.net WestNet: Connecting you to the planet. 805 884-6323 WB6RDV NetLojix Communications, Inc. - http://www.netlojix.com/
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