To clarify, I'm working on a project on an esp8266 (specifically an esp-12s using NodeMCU 1.0).
I have a bunch of html files and images that I bundle into a LittleFS binary that gets written to the flash using esptool (or the arduino ide, which uses esptool internally anyway).
To store the user's settings, I also create a file with the intention of serialising that data to the file.
Unfortunately it crashes and resets as soon as I call LittleFS.open(path, "w");.
So I just need to know, if I compile and upload a filesystem, is that filesystem "Read only"?
(If the answer is yes, then I know I need to use a different method to save user data, if it's no, then there's a bug in my code somewhere)
No, a filesystem image written to flash is not read-only. It's usable exactly as if it had been created by the firmware. There is no discernible difference to the software running on the ESP8266.