I'm using a Nexus 5 (hammerhead) and was running CyanogenMod 13. I used CyanogenMod Recovery to wipe /data and /system, but to sideload a different ROM, a quick Google search told me I needed to update adb on my Ubuntu 14.10 install.
However, after updating adb to 1.0.32, doing
adb devices shows my phone as unauthorized, and thus I cannot flash, push or sideload to the device whatsoever. I can't authorize it either, because I have no Android or CyanogenMod on the device to receive the authorization request.
How do I fix this?