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?

  • Simple - ditch CM recovery and go TWRP.
    – Andy Yan
    Commented Dec 7, 2016 at 1:33
  • I can't flash a new recovery without adb being authorized for my device. Using fastboot flash twrp.img only gets me a <waiting for device> until I terminate the command. Commented Dec 7, 2016 at 1:36
  • That only means you should sort out issues with your fastboot driver...
    – Andy Yan
    Commented Dec 7, 2016 at 1:49
  • Where do you suppose I start? Commented Dec 7, 2016 at 2:23
  • Don't worry about it, I managed to figure it out. I'll answer the question. Commented Dec 7, 2016 at 2:34

1 Answer 1


I learned that fastboot requires the phone to be in the bootloader, not recovery. I was able to flash a new recovery using fastboot flash recovery recovery.img.

  • Derp, that was an unexpected mistake... Glad you sorted it out though :)
    – Andy Yan
    Commented Dec 7, 2016 at 2:48
  • I further ran into an issue (which might have been the biggest problem to begin with), where a partially incomplete wiping of /system and /data prevented me from properly mounting either. Reformatting them fixed the issue, and I was able to then sideload my ROM. Thanks for pointing me in the right direction. Commented Dec 7, 2016 at 23:29

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