Today I was updating IOS on a Cisco 877 router, and a problem came up: the installed flash memory wasn't enough to hold both the old and the new IOS images, so the new one couldn't be uploaded unless the old one was deleted first.
This of course means that, as soon as the old image was deleted, any problem while installing the new one would have rendered the router unbootable; F.E. a power loss would have been especially nasty. Of course, the inherent slowness of a TFTP upload to flash memory didn't help.
Any workaround for this, other than installing a bigger flash card? The two images were both only sligthly bigger than 50% of the total flash memory size, thus even a little space saving would have been enough; I'm thinking about file compression or something similar.
Best Answer
There isn't really a solution, from a file compression standpoint, that you can use. The router's bootloader decompresses the IOS image and, since you can't alter the bootloader adding support for new compression algorithms isn't possible.
Having an out-of-band management connection would the best techncal means to safely handle these situations. In the case of a remote device (one where you can't just walk over to it and plug in your console cable), unfortunately, you could be talking about expensive things like serial terminal servers.