Unable to flash a recovery using Clockworkmod I'm trying to install Cyanogenmod 11 onto an unlocked HTC One, but when I went to boot into recovery mode, all I got was a red error triangle. The docs don't mention it anywhere, but other reports of this error suggest that I first need to flash a custom recovery image.

So from there I discovered Clockworkmod and installed their ROM Manager app. It detected my phone version, but when I select "Flash ClockworkMod Recovery", it successfully downloads something, but then reports "an error occurred while flashing your recovery".

How do I fix this?
It looks like the CyanogenMod installation instructions for M7 are missing a section for flashing ClockworkMod recovery onto the phone.  Right after you unlock the bootloader, you need to do the following:


Download and install Android SDK Tools from here (expand the "Download for Other Platforms", and it should be under the "SDK Tools Only" section.)
Download the latest version of ClockworkMod Recovery image from here.  Scroll down to "HTC One" and select either the regular or touch recovery.  Save the .img file somewhere on your computer.
Download and install USB drivers for the phone.
Restart your phone in bootloader mode by turning it off, and then turning it on while holding the Volume Down button.
Connect the phone to your PC via USB cable.  Your PC should recognize it.
Open Command Prompt (assuming Windows here) and navigate to the platform-tools subfolder of where you installed the SDK Tools (e.g. cd C:\android-sdk\platform-tools)
Ensure the connection works by issuing the following command: fastboot devices This should show you the serial number of your phone.  If this returned nothing or gave you an error, something went wrong during USB driver installation.
Flash the recovery by using the following syntax: fastboot flash recovery [path-to-recovery.img-file].  For example: fastboot flash recovery c:\recovery-clockwork-touch-6.0.4.6-m7.img This sends the recovery image to your phone and flashes it.  Wait for the success message.
Issue the following commands: fastboot erase cache followed by fastboot reboot-bootloader


Your phone should reboot back into bootloader mode, and you should now be able to enter recovery and continue with flashing CM.