I use a 3845 cisco router and need to upgrade an ios but there is not enough space to accomodate the latest version with the one that is currently running. My question is can I erase the current one befor updating with the latest? would it boot after I have deleted the the current one?
Oussama summarizes the procedure. Router should not automatically reload with an ordinary flash load.
When changing IOS, you should also check whether boot is defined in config or whether there are any other IOS versions on same or different flashes. This to insure if there's more than one IOS on the system, system boots the one you desire.
BTW: The 3845 might supports some USB devices. Might also even support booting from them. If so, its another possible option for storing an IOS image on the router.
The command 'boot system tftp ios_image ip address' would help boot the router from the IOS on a tftp server only if there is a working IOS image as the first file in the flash. You can not boot the router from an IOS on the tftp server without having an IOS image in the flash. This is because, the router's interface would not come up and have an IP address on it without an IOS, thus stopping all communication.
You can definitely copy an IOS from a tftp server when the router is in ROMMON using TFTPDNLD procedure, but that's different.
Lawrence, in response to you query, as has been already said - yes, you can delete the file even before you copy the new one. However, you need to ensure that the router is not rebooted till the time the new IOS is not copied. Even if its rebooted accidentally, there are ways to recover it.
Once the new file is copied, issue - show flash: to see if the new image is the first file (which it would be if you erase the flash and not just delete a specific file). If yes, you can safely power cycle the router. If its not the first file then include a boot statement in your config.
boot system flash:
Do keep in mind that the file_name is case sensitive.
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