Restoring or Upgrading the Cisco Router IOS
What happens if you need to restore the Cisco IOS to flash memory to replace an original file that has
been damaged or if you want to upgrade the IOS? You can download the file from a TFTP server to flash
memory by using the copy tftp flash command. This command requires the IP address of the TFTP host
and the name of the file you want to download.
But before you begin, make sure that the file you want to place in flash memory is in the default TFTP
directory on your host. When you issue the command, TFTP won’t ask you where the file is, so if the file
you want to use isn’t in the default directory of the TFTP host, this just won’t work.