What needs to be done when upgrd_ckvX.bin states there is not enough space in /nas/dos?

What needs to be done when upgrd_ckvX.bin states there is not enough space in /nas/dos?

A.
Extend /nas/dos file system

B.
Remove old NAS versions

C.
Check for latest version of upgrd_ckvX.bin

D.
Re-run upgrd_ckvX.bin with a option