Upgrading a Cisco 3750 IOS from a .bin image file

I just wasted hours trying to figure out how to upgrade a Cisco Catalyst 3750 using the .bin image instead of the .tar archive, since I don’t want any fancy web interface on any of my core network devices.

All of the current documentation explains only how to use the archive command, which can’t be used in this case, and I’ve tried /imageonly option to download-sw which still needs the .tar archive. And the only bits of documentation I found which referenced the .bin method were actually misleading.

The solution is quite simple : Just copy the image you want to the device, I did that using xmodem since I was too lazy to plug in a network cable (yeah, old school, especially given the archive tool doesn’t even support xmodem!). Of course, you can use tftp or any other supported protocol :

copy xmodem: flash:c3750-advipservicesk9-mz.122-35.SE5.bin

Once the copy is over, the file is on the flash filesystem. Now comes the trivial yet tricky part : How to activate the image. A quick look at the boot vars show which image will be used. Here we see that it’s still the original one :

Switch#show boot
BOOT path-list      : flash:/c3750-ipbase-mz.122-35.SE5/c3750-ipbase-mz.122-35.SE5.bin
Config file         : flash:/config.text
Private Config file : flash:/private-config.text
Enable Break        : no
Manual Boot         : no
HELPER path-list    :
Auto upgrade        : yes
Auto upgrade path   :

And all of the documentation I found references the boot command to select which image to boot, even a Cisco Wiki page for the 3750 (which I suspect was wrong about this). That command doesn’t seem to exist on the 3750. The proper command is this one, run in configure terminal mode :

boot system flash:c3750-advipservicesk9-mz.122-35.SE5.bin

It does seem completely obvious now, but I had it in front of my nose for hours without seeing it in any Cisco documentation. Running show boot again will now list the new image :

Switch#show boot
BOOT path-list      : flash:c3750-advipservicesk9-mz.122-35.SE5.bin
Config file         : flash:/config.text
Private Config file : flash:/private-config.text
Enable Break        : no
Manual Boot         : no
HELPER path-list    :
Auto upgrade        : yes
Auto upgrade path   :

Then just reload the switch and you’re done. You can later remove the older image using delete /force /recursive, but you can also just leave it, as the switch will automatically boot the first image it finds alphabetically if the ones from the boot path-list aren’t found.