I've got an Archer C5 that's probably on OpenWrt, and I'm thinking of bringing it back to stock firmware.
In fact I've got two Archer C5 routers, one of which is on stock firmware and is in active use. The other one is gathering dust. I believe I put OpenWrt on it some time ago, for the purpose of an embedded-device hobby project that has now long been abandoned - and I've decided that if this project were ever to resume and I needed another OpenWrt router for it, I'll get a new router.
I'm sure I'll be able to figure it out but is there an easy way? I anticipate that I'm likely to need to reset the OpenWrt root password first. There's a USB memory stick attached to it, so I also anticipate there's an external root file system, and that the root password when the external root file system is present also might not be the same as what it is when the external root file system isn't present; ideally I'd also like to check if there's any files I might want to keep too. Thanks.
Well - if it's got DHCP server running, it's relatively easy to find out whether it's on stock or OpenWrt; just grab an IP address, then check the gateway (or nmap the subnet on the offchance that the DHCP-configured gateway address is different to the router's static address) - and it's plain-sailing from there.
But if there's no DHCP? Perhaps try the stock-firmware factory reset procedure, hold the reset button in for 10 seconds after the LEDs have settled. If it's on stock, this will work (and will also enable DHCP server). But if it's on OpenWrt, this won't work. Still, it's relatively easy to get into failsafe mode; just power-cycle it, and when the LEDs start blinking, press a button. If the LEDs start blinking faster at this point, you've successfully put it in failsafe.
Only further hurdle I hit was that the command to reset it didn't work; apparently there was a bug in that version of OpenWrt, but an alternative command worked. Once reset, logged into LuCi and used it to revert back to stock firmware - and I now have an extra working 5GHz wifi access point.