(Self answering here because I only found this answer after hours of dredging through 200 page threads of forum posts.)
There are two non-standard but semi-prevalent methods that may work depending on your make and model (and why recovery isn't working in the first place).
Some phones actually respond to fastboot reboot recovery. This is quite natural ...
If you check with our fastboot tag-wiki, and follow up the link to the List of fastboot commands, you will see the answer is NO. Fastboot only has commands to write to the device. A few exceptions include:
making sure there is a device at all, using fastboot devices
some OEM specific commands to read configuration values (fastboot oem <option> – note ...
To make the system recognize the Android device, in their several modes, one needs to set permissions for his user in udev.
You need to repeat this process of loading Android udev IDs, for every mode the phone has (operating system, bootloader or recovery) because they have different USB IDs
# reboot into fastboot mode
adb reboot bootloader
# grab you ...
By looking at the inf file, you can find that it tells to use the WinUSB driver. So there is a better solution than disabling driver signature enforcement, you can use the tool Zadig (http://zadig.akeo.ie/). This tools create a self-signed inf for this specific device, using ephemeral keys, added to the trusted certificate store (for this only device / inf), ...
I encounter the same problem today :)
flash-all script failed when writing userdata
I have managed to solve this issue by manually continue the flashing process:
1) extract image-hammerhead-m4b30z.zip
2) cd to the extracted folder
3) run the following commands (one by one)
fastboot erase userdata
fastboot flash userdata userdata.img
fastboot erase cache
For future reference, this was my related case (involving a Nexus 4):
I tried to bring my phone back to the original state (bootloader locked + stock rom).
Now fastboot devices did not show the device where adb device did, until I put the phone in fastboot mode (this makes sense, but took me a while to figure out...)
To put the Nexus 4 in fastboot mode:
Problem solved. At the end I saw that drivers for android were not installed. I installed drivers from this site http://forum.xda-developers.com/showthread.php?t=2126036 and device is visible by fastboot. One thing I don't understand is why adb saw device and fastboot not.
I found the solution myself: Windows 10 somehow does not want to install the driver, as it can not verify the manufacturer. So the driver from Sony Developer's site works just fine.
After deactivating the Windows driver signature check everything works fine.
To deactivate proceed like this: (taken from HERE)
Press Win + X then U then Shift + R
This thread on XDA has a post
....what is the aim of the "fastboot erase modemst" command?
modemst1 and modemst2 are storage partitions for Radio Firmware .... - and it's obviously a recommended practice to wipe these partitions when flashing a newer Radio Firmware
This XDA thread is all about fastboot commands
fastboot erase system
That's expected. Devices with A/B partition scheme don't have a recovery partition. You can only boot in recovery mode with fastboot boot twrp.img. But to permanently flash recovery to device which can be booted into by proper key combination, you need to unpack both of your boot.imgs (A/B) from device and replace the ramdisk with the one extracted from twrp....
ADB and fastboot require different USB drivers.
Whilst you may see your device under adb when your phone is on it will not be detected by fastboot until you install the driver for it and hence will show "waiting for device".
You can follow the steps below to do so:
Open your device manager and reboot your device into fast boot by pressing volume up, down ...
Details for that can be found in our usb-debugging tag-wiki (where I've just added them):
By default, USB debugging is disabled with stock ROMs (some custom ROMs however have it enabled by default). To toggle it on or off, you can find the corresponding switch in Settings › Development – a section originally hidden with Android 4.2 and up. You can make ...
To answer your question specifically: In Moto devices, Preflash Validation Error means the factory image you are attempting to flash is older than the one you have currently installed and Moto devices do not support downgrading of the bootloader or partition table (gpt.bin) regardless if the bootloader is locked or unlocked.
There is also a second issue ...
Yes. Locking the bootloader is possible after you have installed a custom firmware.
A locked bootloader will not allow you to ad-hoc boot custom binaries (using fastboot boot boot.img and will not allow you to directly write to the flash chips. An unlocked bootloader however does offer you this and newly available commands are:
fastboot flash partition ...
Assuming your device adheres to some Android standards, you'd want to run fastboot oem device-info.
Often you can also run fastboot reboot-bootloader to get into the bootloader which often says right there on screen whether it's locked or not.
Different devices can display the lock state differently.
fastboot is located in %ANDROID_SDK_DIR%\platform-tools,...
Step 1: Unlock the bootloader; fastboot oem unlock This WILL wipe your device. Skip if already unlocked. Set up your device and put SuperSU.zip into it.
Step 2: Download the appropriate TWRP/CWM image for your device.
Step 3: Boot your phone into bootloader; adb reboot bootloaderwhile the device is on or hold the power button and the volume down button while ...
Fastboot allows you to send commands to your phone while in the bootloader. The bootloader is the one place that ADB is not running.
Disclaimer, not all of these may work with your device.
fastboot oem unlock
Unlock your bootloader. If your device supports this, you can unlock your bootloader here. Most phones require an exploit in order to gain root ...
There is no Fastboot Command that does this.
However you could try holding the power button down until the screen goes blank and then letting go off the power button before the device starts to boot (before the vibrate). This is the only viable way... The list of available Fastboot commands are:
usage: fastboot [ <option> ] <command>
Episode 3: Return of the Shell.
If I ever had any chance of solving this, I first had to figure out why the shell wasn't working. adbd itself was responding, so it was started on the tablet side - but it could not execute the shell, even when I hack-patched it to invoke a file (/sbin/sh) that I myself placed in the boot image - being 100% sure that it had ...
I too faced this issue and issuing the fastboot commands manually (instead of relying on flash-all) and it worked well.
These are the commands to use (just forget everything and make sure these commands are executed in this order with the appropriate .img file available):
fastboot flash recovery recovery.img
fastboot flash boot boot.img
fastboot flash ...
When you use fastboot boot FILE.img, the image is downloaded and written into the RAM and than the normal procedure to boot a boot.img is followed. No changes to any partition takes place.
If the image is invalid or cannot be booted into, the boot process automatically falls back to the image in the boot partition. Once the temporary kernel is booted into, ...
First you need the actual fastboot, e.g. 1.4.3 (from link in the other answer).
Then the correct command is:
In the help (fastboot help) you can read in fastboot version 28.0.3:
--slot <slot> Specify slot name to be used if the