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[TUT] How to use fastboot on our device

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By laufersteppenwolf, Inactive Recognized Developer / Retired Forum Moderator on 26th May 2013, 06:43 PM
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As you can see in the title, i decided to write a small fastboot tut, especially for our p880 and its "own" commands and tricks
I am, as always, not responsible for what you do with your device. Do it on your own risk.

I will however not explain on how to set up fastboot on your PC. There are tons of tuts out there on xda, just search for it
NOTICE: You need an unlocked bootloader for this

Screenshots will be added later, 'cause my lappy is compiling right now and i thought i could use the time to write this so just wait a bit

Now, lets begin with the fun, shall we?


Fastboot is usually quite easy to use. But if you went searching for a tut on the web, you might have noticed that it doesn't work the way it should on your device.
That's because LG messed something up in the bootloader, but let's don't worry about that now, it does work nontheless

Fastboot is "a part" of the bootloader. This means, neither the kernel (boot), nor the recovery gets booted.
That gives you the ability to flash, but also boot kernels/recoveries. And yes, i meant booting, without really flashing it

Now we need to get into fastboot mode:

And this is (one of) the point(s) where LG messed up. The usual command is "adb reboot bootloader". But this command does not work on your device the way it should.
It gets you into a kind of fastboot mode, but you can't flash anything, because it says the bootloader would be locked, even tho it isn't.
The working command is
adb reboot oem-unlock
i guess this command sounds familliar, doesn't it? and don't worry, it will not lead you to a menu that deletes your data.
It will lead you to the working fastboot mode

now we're in the working fastboot mode. To check if you've set up fastboot correctly, type
fastboot devices
this should list your phone and its serial number.

It is recognized? good. so now we might want to check the status of our device (BL unlock state, serial number,...).
Therefore type
fastboot getvar all
now you can check whether it's really unlocked or not.

If everything's fine, you might want to...

Flash something

In order to flash something, you need the appropriate image. For kernels it's mostly "boot.img"
The command to flash something via fastboot is in general
fastboot flash <partition> <filename>
Example: You want to flash a kernel (named test_boot.img) and you have downloaded the kernel to the folder where your fastboot.exe is.
So you type
fastboot flash boot test_boot.img
This will copy the kernel to your device and then flash it to the LNX (boot) partition.

Of course you can flash other partitions, too, like system, data, cache, recovery...

After a flash, it is wise to clear the cache, or even your /data partition...

Deleting a partition

You don't need a recovery to wipe a partition, just use fastboot

The general command is
fastboot erase <partition>
For our example it's enough to wipe the cache. You can do this using this command:
fastboot erase cache
Also here you can wipe all partitions, like system, data, cache, boot, recovery...

So now we've flashed what we wanted to, wiped the needed partitions, but how do i..

Get out of fastboot

This is as easy as getting in just type
fastboot reboot
to reboot the device (Here's another thing, where LG messed up.... it reboots, but stays at the LG spash screen.
So press the power button for at least 10 secs. Now your device will reboot into recovery (!?)
then just tap reboot system now and be happy )

fastboot continue
this one will not reboot the device, but continue the boot procedure. I, for one, would suggest you to use the first command

now your device will boot up normally (except your kernel/system.... has a bug of course )

for more help, just type
fastboot help
and the last point is...

Bricking the device
nah, just kidding
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26th May 2013, 06:43 PM |#2  
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26th May 2013, 07:48 PM |#3  
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Thanks for this usefull post!

Sent from my LG-P880 using xda app-developers app
31st July 2013, 12:18 PM |#4  
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thanks, it's very useful for me.
31st July 2013, 01:06 PM |#5  
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it's so easy
2nd August 2013, 11:45 AM |#6  
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fastboot boot <kernel> <ramdisk> -c "androidboot.mode=normal"

<kernel> is the kernel zImage
<ramdisk> can be a .img, .cpio, .cpio.gz

-c "androidboot.mode=normal” is needed the get the kernel booted for the p880 with the correct commandline

Gesendet von meinem LG-P880 mit Tapatalk 4 Beta
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5th August 2013, 08:07 PM |#7  
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So, to get into fastboot mode, I have to turn on my phone, plug it to my computer and in cmd I type adb reboot oem-unlock, right? Is there any possibility to access it in case of a bootloop or something?
7th August 2013, 09:05 AM |#8  
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boot into recovery system by holding power+vol-down till it vibrates, then use either adb to issue the command or when using twrp as recovery system: Reboot --> Fastboot

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10th October 2013, 12:43 PM |#9  
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A little update from LG...

I wrote them that they have messed up our bootloader, and told them the bugs/problems/... well, see yourself:


1) "adb reboot bootloader" doesn't bring me into bootloader. Well it does, but even though i have unlocked the bootloader, it still says it would be locked.
instead i need to use "adb reboot oem-unlock" to get into bootloader.

- P880 does not support "adb reboot bootloader" to go into bootloader. P880 only works "adb reboot oem-unlock" instead of "adb reboot bootloader" to go into bootloader. and then you can use the fastboot command mode after accept unlock bootloader.

2) "fastboot reboot" partly reboots the device, but then it keeps stuck at the first LG splash screen. pressing power button for 10 seconds brings me into recovery then, instead of into the ROM.

- P880 supports "fastboot reboot", before flashing the customize image, "fastboot reboot" reboot normally.

3) "fastboot flash system [path/to/system.img]" gives me "fatal error: unknown partition"

- P880 can only flash boot, recovery. Ex> fastboot flash boot/recovery boot.img/recovery.img

4) "fastboot boot [...]" doesn't work at all.

- P880 does not support "fastboot boot [...]" command

- P880 supports only flash, erase, reboot as you already seen in bootloader unlock warning message.

5) I have found no way to boot into fastboot/bootloader without a booting phone. Maybe you could try to add the possibility to boot directly into fastboot.

- You can only go into fastboot mode using "adb reboot oem-unlock"

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10th October 2013, 02:25 PM |#10  
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lg is retarded, but hey atleast they had the decency to answer
10th October 2013, 03:59 PM |#11  
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Yeh, you need to kdz flash if you mess up both system and recovery.
Keep an suid busybox in /data so you can root and re-flash CWM/TWRP in the backup+restore mode without having to clear data so the stock ROM can boot.
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