I would not recommend trying to update base-files. The scripts and config defaults included can be pretty tightly tied to certain core packages, so having a mix of core packages and base-files from different builds can lead to unexpected results.
[quote="luup, post:3, topic:365"]
how should I upgrade my base-files as there is no custom ugrade image for my Cisco Meraki MR18.
[/quote]Likely you need to upgrade the whole firmware the same way as you originally installed it (if there is no upgrade image). In general, there is no reason to upgrade base-files separately. They are more or less part of the core firmware.