[Guide] How To Setup And Use Fastboot

First a short explanation:
Fastboot, like ADB, is a tool to communicate from PC to Android phone. There are times when it is a must to use, and times when it is just helpful.
ADB is used within your recovery or within your OS, but when you are in bootloader mode and need to communicate with your phone then you need fastboot.

And you may ask why would i ever need this?
Well many reasons. Main one is knowledge, learning the ins and outs of fastboot, like learning ADB, can get you out of many jams.
And if you want to unlock your bootloader this is done through fastboot. Granted HTC's unlock is... well crap, but for a Nexus this is how its done.
One other reason I have to stress is learning for safety reasons, This is about the safest way possible to flash firmware to your phone (ie Radio, Hboot, Recovery)

Lastly you may want to know the limitations,
There are many of course, this isnt JTAG, it will not resurrect a hard brick, but it often save peoples phones from 'soft bricks' and lots of time when know how and when to use it.
Think of fastboot as the program that takes over when ADB cant be used, it works with firmware more than software.

So where do i get fastboot? There are a few ways but most often I would recommend getting it from the Android SDK as it is will be up to date.
or you can use THIS HANDY TOOL created by @shimp208

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Fastboot is a protocol designed to flash signed/unsigned partitions to android phones directly into the phones flash memory. If you are familiar with ADB think of it in the same way.
If you're not, just understand it is a tool designed to help flash images such as recoveries, bootloaders, kernels, etc. to your android phone. For the most part you can not use much of fastboot unless you are rooted and have an engineering SPL (Hboot/Bootloader)
If using a Nexus device you in a sense have an engineering bootloader already so don't need to worry about it like HTC folks need. But Some Nexus lines will have different bootloaders with different capabilities.
This however is not a tutorial to root your phone so i will not explain this. I will though go over SOME basics as in unlocking your bootloader to allow it to be rooted.

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For many phones this is necessary to root, for others it is a poor way to root your phone as you may not have full access.
Many HTC model phones can be rooted with various exploits, sometimes removing the radio secure flags completely.
If you have one of these devices than I recommend this, as true radio s-off is far superior to an unlocked bootloader.
But other phones, including the Nexus line, will be fine just unlocking and do not need to worry, Although some phones like the Nexus One can profit from a new bootloader altogether.
To begin the rooting process you simply need to unlock your bootloader with this command from a terminal/CMD

Code:

fastboot oem unlock

and the reverse of course is

Code:

fastboot oem lock

Be prepared for a full wipe of your phone when unlocking the bootloader!

But quickly if you have an HTC and choose to unlock your bootloader to root your phone follow these step:

Select your phone from the list HERE (you will need to create a log in)
there will be some legal mumbojumbo to click through (just saying you void your warranty but you knew this!)
you may need HTC sync found HERE as well as the proper RUU for your phone, the HTCDev site will inform you.
After which the site will move you through the steps to gain fastboot access, but if you followed my guide above just skip it all.
next you will need to get the identifier token, this is unique to your device and really just getting probably voids your warranty,
even if you stopped the guide here. to do so, open terminal/CMD and type

Code:

fastboot oem get_identifier_token

copy and paste this information into the prompt at the bottom of the page. Now wait for an email to get your token....
once you get the email with the token you can now follow their steps to unlock your bootloader...
really if at all possible i recommend not to do this method of rooting. But if you do, follow these same next steps that the Nexus devices will be doing...

Now that your bootloader is unlocked:
We will flash a custom recovery to your phone, then a custom already rooted ROM. To flash the recovery go to your device specific forum HERE and find the developers section.
Look for a custom recovery option and consider reading up on it there.
Different Android phones will have different custom recovery options depending on the developers for it. The most common is ClockworkMod, there are both touch and none touch recovery options.
some others are TWRP, 4EXT, AmonRa and Cannibal. Find out what your options are, pick one and download it.
If possible check the MD5Sum, Windows use: THIS and Linux use a terminal and type

Code:

md5sum <filename>

of course replace <filename> with the file name.
View attachment 1980095
If you prefer, GTK Hash is a nice program as well.
Now this should be an image not a zip, so if the extension is .img your good, if its in a .zip or .jar or whatever extract the image.
Take this image and (for simplistic sake) name it

recovery.img

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**if using windows be sure to pay attention if your file extensions are hidden, don't name it recovery.img.img!
So be sure your phone is in fastboot mode and connected to PC, open a terminal/cmd in the same location that recovery.img is in
(cd to that directory or windows users can hold shift > right click in the folder it's in > choose open command here)

Code:

fastboot erase recovery
fastboot flash recovery recovery.img

**erase recovery is not necessary but i am OCD about wiping...
now if you get an okay! then your good :good:

Code:

sending 'recovery' (4930 KB)...
OKAY [  0.521s]
writing 'recovery'...
OKAY [  0.489s]
finished. total time: 1.10s

If not let me know what the output is and ill help you fix it. (I will also make a troubleshooting section in my final post)

Great! Now Let's Flash a ROM
In that same developers section for your phone, you should pick out a ROM of your licking. If possible i would suggest an older version of CyanogeMod as these builds tend to be quite stable.
Also some phones may have newer ROMs requiring you to do various things to your phone. Such as changing radios or bootloaders or other things we haven't gotten to yet.
So for now try to read the OP of the ROM you like and make sure you meet all requirements.
So Im not going deep into how to flash a ROM from recovery as this is not part of a fastboot guide.
But pretty much just pick a ROM and anything else you may need (gapps, kernel, etc) and put on root of SDcard (no other folder)
Then boot to recovery, wipe all you can (I'll teach you fastboot wiping soon!) and then flash ROM + whatever else you need to and then reboot.

Another Issue With HTC's Unlocked Bootloaders

Well if this not yet another reason to try to gain true radio s-off for your phone...
From with in that ROM that you flashed you also need to unzip and extract the kernel (boot.img) this will need to be flashed through fastboot.
Once all the above steps are completed reboot into fastboot mode, if your recovery doesn't have a quick way to do so just open a terminal/cmd and type:

Code:

adb reboot-bootloader

from here you will need to then open a terminal/cmd in the same location as that boot.img is and type:

Code:

fastboot flash boot boot.img

If it says okay you are finally done!!! Well done with flashing your first ROM but can you flash a ROM in fastboot? I mean do you need recovery at all?
There are ways, and ill teach ya in the next post!

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We need to download the ROM of choice to your computer. Once complete find the folder that ROM is in and open terminal/cmd to that directory
(quickest way for windows; just hold shift and right click within that folder > open command window here) of course make sure your phone is plugged into computer and in fastboot mode.

Lets see how quick and easy this really is...
In the command line type:

Code:

fastboot devices

Seeing your serial number means we know all is good
Now lets type these commands:

Code:

fastboot erase system -w
fastboot erase boot
fastboot update superawesomerom.zip

Of course replace <superawesomerom.zip> with the correct file name

and last but not least:

Code:

fastboot reboot

*Its been a little while since i did this but the phone might automatically reboot after flash so no need to run the reboot command

As your phone boots into the new ROM, pat yourself on the back...

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You may have noticed earlier that I had you erase your recovery before flashing a new one,
now here I had you erase system and boot, you may be wondering why.
I find that a large amount of complaints in developer threads are due to people not properly wiping before a flash.
Of course there is times when a 'dirty' flash is fine, but if you're ever not sure, wipe as cleanly as possible.
fastboot allows for about the cleanest of wipes by the way. And each partition can be done separately too.

Code:

fastboot erase system
fastboot erase data
fastboot erase cache

can all be done individually, but to do these all in one command

Code:

fastboot erase system -w

If possible I recommend to do these steps before flashing a ROM, and now that you know you can do this all within fastboot mode i suggest to try it out, its quick and painless!
Don't forget to wipe your kernel too! (fastboot erase boot)

~Important~ If your device uses an emulated SD card (as in no removable micro SD but an SD partition on phone)
Then be careful wiping data/userdata as this will erase all contents of internal SD - you are forewarned!

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Sure this can be done, hell you can restore a nandroid if you want!
well first you need to make a nandroid back up (unfortunately fastboot cant make a nandroid for you :crying: ) Put it some where on your computer.
Personally I only keep maybe 2 or 3 nandroids on my phone's SD card as why waste space. I do however keep almost all my nandroids on my computer separated into different folders for different phones. So my path to a nandroid backup would be something like:

android/htcg2/nandroids/<nameofnandroid>

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But here's the catch, most newer recoveries do tar backups I believe TWRP uses .win, these can not be flashed in their current form!
However most older recoveries use yaffs2 format for their backups, these will always work. Pretty much if you get a backup with various partitions as .img you're good to go!
**Hypothetically speaking here: you installed a new recovery and want to flash a nandroid made in old recovery but the two recoveries used different formats...
Well you can flash the images with fastboot, then make a new nandroid and you got them back!
...Maybe I'm stretching... oh well, here's how to!

Now the obvious stuff:
Have phone plugged into PC via USB and in fastboot mode, open terminal/cmd and change directories to that folder where your nandroid is in (or again just hold shift and right click > open command window here if using windows)
Now in terminal/cmd type:

Code:

fastboot devices

all is good when serial number is displayed, now type:

Code:

fastboot erase system -w
fastboot erase boot

*This isn't 100% necessary but I'm a firm believer in wiping before any flash, even a backup

Code:

fastboot flash userdata data.img
fastboot flash system system.img
fastboot flash boot boot.img
fastboot reboot

(of course change the image names if needed)

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Some phones will not allow bootloader flashes unless you remove the radio secure flags, if you have a phone like this check the developers thread for a how to.
To begin, find the appropriate bootloader (sometimes referred to as an Hboot or SPL) for your phone,
Now download and check MD5sum, have your phone in fastboot mode and open a terminal/cmd in the location your Hboot.img is stored.

Code:

fastboot devices
fastboot flash hboot hboot.img

and of course replace 'hboot.img' with whatever you titled your image
**Do not reboot if you see 'sending.... failed' need to see the 'okay!'
I am not trying to scare you as these instances are so rare, but knowing what to do ahead of time is just common sense.

Not all devices use the same terminology for partitions, so if the above does not work than consider changing to this command:

Code:

fastboot flash bootloader bootloader.img

Again replacing <bootloader.img> with the name of your image

Now flashing a new bootloader will more than likely repartition your phone, so from here you probably should flash a new recovery, then flash a new ROM.
Be prepared to do all this before flashing a new Hboot!

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Flashing a radio can also be dangerous, but again the safest way to do so is within fastboot. So if possible always flash radios in fastboot mode!
**I am not referring to the FM radio in your car, rather your cellular Radio, you know where you get reception... don't ask me how to add a FM radio to your phone!
Also know OEMs commonly use baseband and radio as interchangeable terms, for the most part this is the exact same thing

First things first, know why you are flashing a new Radio. Is it because you have poor reception? Poor data speeds? Poor battery life?
Yes a new radio can cure all this, but NO ONE can tell you which radio is best for your phone, not even someone living in the same city.
The best radio for my phone will not for sure be the best for yours, even if you live down the road from me. Don't ask what Radio is best! and only flash a radio meant for your device!

Now that that's out of the way, lets do the same steps as before:
Download appropriate radio
Extract if needed (should be in .img format)
For simplistic sake name it 'radio.img'
Plug in phone to PC and open a terminal/cmd in the same location as your radio.img

Code:

fastboot devices
fastboot flash radio radio.img
fastboot reboot-bootloader

Again only reboot if all goes well (It will if you follow all direction)
Upon rebooting your bootloader you will notice your radio version has changed, congrats! You're becoming a pro!

*note, occasionally OEMs package another image called rcdata.img along with a firmware release, if they do I also recommend to flash this along with the radio

Code:

fastboot flash rcdata rcdata.img

**another note, if possible try to match the ril libraries between your ROM and radio, this is device specific and you will need to see your developers thread for this info.
It is not always possible or necessary to do so, but many do say it help quite a lot

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Earlier I went over flashing kernels as part of HTC Unlocked Bootloader Flashing, the process is the same for anyone else as well.
Locate the Kernel you want to flash
navigate to the folder it is in (should be in .img format and lets name it boot.img)

Code:

fastboot flash boot boot.img

But lets say you are a developer and have worked on a new kernel for your device, a quick and easy way to test it out may be to fastboot load the kernel:

Code:

fastboot erase boot
fastboot boot kernel ramdisk

As usual replace file/image names accordingly
If you do not want to erase the current kernel, just skip erasing.
But I would just have a working kernel.img handy and erase, this way I know there are no residual effects from previous kernel - choice is yours

Code:

fastboot flash:raw boot kernel ramdisk 
fastboot reboot

Test it out and see how things go! Good luck! :good:

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