While working on a complex partition scheme for a NixOS installation, an unexpected hurdle appeared: getting the system to boot. With most Linux distributions, a helpful feature exists where you can gain access to a shell simply by entering the root password if booting goes awry. However, this isn’t the default behavior for NixOS, and discovering how to activate it took a fair bit of digging.
The actual solution for NixOS involved adding a specific kernel parameter,
boot.shell_on_fail, to make this feature available.