issue to format flash in cisco 3850 from rommon mode

[coolj_212]

switch:  format flash:
Are you sure you want to format "flash:" (all data will be lost) (y/n)?y
Filesystem "flash:" not formatted -- invalid argument

[balaji.bandi]

I am not sure you able to do that, i believe i tried and it failed for me too.

1. Boot from usbflash0: and after successful boot from usbflash0:

2. Format flash: 

3. Copy the IOS XE what you looking to upgrade from usbflash0: to flash:,

4. change the  "boot system switch all flash:version.bin.

5.reboot

Make sure you have back of the config to restore.

[00u1ab28axbOOzhqE5d7]

Emergency install from usb will format the flash.