Router#copy run start
Destination filename [start]?
Erase flash: before copying? [confirm]
Erasing the flash filesystem will remove all files! Continue? [confirm]
Erase of flash: complete
Verifying checksum... OK (0xA83F)
7056 bytes copied in 0.836 secs
To erase any files on the Flash device, including the Cisco IOS Software file, select Enter at the Erase flash: before copying? [confirm] prompt. The router then reloads and goes into ROM Monitor (ROMmon) mode.
To resolve this issue, enter n so that the Cisco IOS Software file in Flash is not erased. The running configuration file is copied into Flash, but the Cisco IOS Software file also remains on Flash, leaving the router bootable.
As a workaround, issue the write memory command. This saves the running configuration to NVRAM, as this command never prompts to erase Flash.
If Flash has already been erased, do not reload the router because it will go into ROMmon mode, since no Cisco IOS Software image is present on Flash.
Copy the Cisco IOS Software file back into Flash before reloading the router.