CCR2004 upgrade failed “free XXX kB disk space for a (null)upgrade” – working upgrade path to 7.21

Yes, this is very good advice. :slightly_smiling_face:

It is not entirely clear (to me) the relationship between Routerboard firmware and RouterOS version, in theory - unless the routerboard firmware is much older than OS - it should make not a difference, in practice it does in many if not most cases.

Hence Rule #9:
The twelve Rules of Mikrotik Club