OpenWrt allows you to boot into a failsafe mode that overrides its current configuration. If your device becomes inaccessible, e.g. after a configuration error, then failsafe mode is there to help you out. When you reboot in failsafe mode, the device starts up in a basic operating state, with a few hard coded defaults, and you can begin to fix the problem manually.
Failsafe mode cannot, however, fix more deeply rooted problems like faulty hardware or a broken kernel. It is similar to a reset, however with failsafe, you can access your device and restore settings if desired, whereas a reset would just wipe everything.
Caveat: Failsafe mode is only available if you have installed firmware from a SquashFS image, that includes the required read-only root partition. To verify whether your device has the SquashFS root partition, check for “squashfs” either in the OpenWrt image name or perform the following check on your device:
grep squash /proc/mounts
The terminal should return something similar to this:
/dev/root /rom squashfs ro,relatime 0 0
Regards,
Rachel Gomez