I landed here because I'm trying to update WRT on my RaidSonic IB-NAS4220-B, and this folder does not contain a raidsonic_ib-4220-...-sysupgrade.bin file, only ...-factory.bin. The Techdata page mentions those ...-factory.bin images as "Upgrade URLs" (and to add to confusion, for some reason it links to ext4 versions, even though by reading this forum I got the impression that a 16M ROM device should be definitely used with SquashFS).
Anyway, after a lot of fearmongering I took my chances and uploaded the ...-squashfs-factory.bin image via the WRT's LuCI interface, and it seems to have worked. So I'm leaving a post here just in case another uncertain noob like me ends up in this thread in similar situation.
yeah i saw "Firmware OpenWrt snapshot Upgrade URL" and assumed it would have a sysupgrade suffix, but i guess not.
nice eye, but i would still use that page as the ultimate guide. i guess you sort of lucked out by not reading the techdata page and still flashing the factory image without issues :>
@ScumCoder Yours is an edge case. When available one should always flash a sysupgrade image to upgrade from OpenWrt, when available.
The fact the factory image is linked for sysupgrade in that wiki page means it's meant to work. However, I think nowadays a sysupgrade image is what gets built by default if you don't tell the build system to provide a factory one - and I think kind of the opposite happened here.
Might be sysupgrade wasn't around or as widely supported when your device gained OpenWrt support.