Database Develop

Problem rooting - Failed: Too many links

I'm having a problem rooting my Nexus One (I have also read the newbie FAQ and searched the forum to no avail) - I have followed the instructions listed on the androidandme site.
When I try to unlock using fastboot I get this returned:
C:\....\Desktop\android-sdk-windows\tools>fastboot oem unlock
... INFOErasing userdata...
FAILED (status read failed (Too many links))
When I start the phone in fastboot mode it now says *** UNLOCKED *** at the top of the screen. I then flashed Amon-Ra's recovery image, as below:
C:\....\Desktop\android-sdk-windows\tools>fastboot flash recovery recovery-
RA-nexus-v1.6.2.img
sending 'recovery' (3954 KB)... OKAY
writing 'recovery'... OKAY
I assumed everything was going to be fine despite the issues unlocking. On trying to boot into recovery mode all I get is a screen with an exclamation mark and the android robot.
On turning the phone on as usual it seems that I can not run "Root required" apps such as the N1 torch.
I have tried running the OEM unlock command again but it seems to think that it has worked, as below:
C:\....\Desktop\android-sdk-windows\tools>fastboot oem unlock
... INFODevice was already unlocked!
OKAY
It would seem from the newbie guide that I still need to flash the recovery image but that seems to be going fine. I can't see that I've messed up so far so is there some way to "unroot" my phone or go through the OEM unlock process again?
Thanks.

You already unlock your bootloader, now put your rom of choice in the root of your sdcard, now flash again
AmonRa recovery, but this time don't reboot, after you you flash the recovery, flash the rom, and reboot.Now you should have su permition. Remember to nandroid backup before flashing the rom.

jongie123 said:
You already unlock your bootloader, now put your rom of choice in the root of your sdcard, now flash again
AmonRa recovery, but this time don't reboot, after you you flash the recovery, flash the rom, and reboot.Now you should have su permition. Remember to nandroid backup before flashing the rom.
Click to expand...
Click to collapse
I tried this, but still don't have root permissions - any thoughts?
I have read and searched and read some more and searched some more, and now just need some help...
Thanks in advance.

2 options, either install superboot from the Modaco's site to gain su, or flash Cyanogen's google adon.

jongie123 said:
2 options, either install superboot from the Modaco's site to gain su, or flash Cyanogen's google adon.
Click to expand...
Click to collapse
I suggest One thing. Pay 15.47 american Usd, at Online Kitchen for Modaco, Viola, Your done, always rooted.. Always Su'd up..
The Bootloader is simple on a windows machine, and so is root.. On Modaco's site there is a whole tutorial on this.. Plus search the threads, a whole ish load too..
i"d pay the 15.47.. Just Nike it, Just do it.. It's so much easier.. Just click-click, bake, download, flash, done..
Go..Go..!

jongie123 said:
You already unlock your bootloader, now put your rom of choice in the root of your sdcard, now flash again
AmonRa recovery, but this time don't reboot, after you you flash the recovery, flash the rom, and reboot.Now you should have su permition. Remember to nandroid backup before flashing the rom.
Click to expand...
Click to collapse
Thanks, I managed to flash the custom ROM this way, however I can't boot into recovery mode unless I boot from fastboot. Is this to be expected or should I be able to just turn on the phone, unconnected to the computer, while holding volume-down and boot into recovery mode?

If you just need root, get 'superboot'. It needs to be flashed to the "boot" partition (after unlocking the bootloader).
What it does is copy the root files to the data ROM and sets up permissions the first time the phone is booted (runs some sort of script I guess).
Link to superboot (free), make sure you get the right version:
http://android.modaco.com/content/g...erd79-epe54b-superboot-rooting-the-nexus-one/

look up "get root back".... Try these commands via ADB:
adb remount
adb shell chmod 6755 /system/xbin/su
....This should "fix_permision" and get you root back, IF you ever had it....

papermonk said:
Thanks, I managed to flash the custom ROM this way, however I can't boot into recovery mode unless I boot from fastboot. Is this to be expected or should I be able to just turn on the phone, unconnected to the computer, while holding volume-down and boot into recovery mode?
Click to expand...
Click to collapse
Using adb you can issue "adb reboot recovery" and wind up in recovery mode. You can also hold down the power button and trackball (connected or disconnected from the computer) and enter fastboot. From there, select bootloader and then recovery.

I am trying to unlock g1 but it fails showing "too many links". It does not do anything else.

sadhuKashmir said:
I am trying to unlock g1 but it fails showing "too many links". It does not do anything else.
Click to expand...
Click to collapse
If you are rooting a G1, correct me if I am wrong, but couldn't you just use one of the one click root methods?
I thought all of the patches denying one click root were contained in official FW's of GB and the G1 did not get it.

Trouble flashing any update.zip

I'm sorry if this is posted anywhere, but I spent a couple hours last night and another couple hours today searching here and in Google with no luck.
-Skip me for TL;DR-
I got a G1 when they first came out, and rooted it as soon as I could. I ran JF1.5 then JF1.6 then after a while upgraded to Cyanogen. It was great and my GF still uses it and loves it. I got a Nexus One about a month after they came out and I've been in love. I haven't went to Cyanogen since, only because the stock rom has been great and I haven't needed any extra features yet.
Now that 720p is available along with a few other things I'd like, I want to upgrade finally.
-TL;DR end-
Basically I'm trying to say I'm not an idiot or very new to loading roms and toying with an Android device.
From past experiences I basically know the process of root/recovery/rom etc.
I loaded froyo onto the phone when it was available via the stock recovery console and an update.zip ... no problems.
Yesterday, I unlocked the bootloader.
Installed Modaco's superboot.
And used fastboot to push recovery-RA-nexus-v1.7.0.1-cyan.img
After that I turned the phone on, and logged in to check it out and make sure I had root. Everything was running great (Froyo saves your app installs in the cloud!!!) and I did, in fact, have root. All seemed well.
-The Problem-
Now, I can't load any more update.zip files. Nothing at all. Stock rom, modded rom, rom updates, anything. When I try to install any update.zip I get the following output:
-- Install from sdcard...
Finding update package...
Opening update package...
Verifying update package...
E:signature verification failed
Installation aborted.
At the top of the recovery screen it reads: Android system recovery <3e>
If that makes any difference....
NOTE: I can still use fastboot to push new recovery images, which I've tried.
System information below:
Fastboot/Bootloader Screen:
NEXUSONE PVT SHIP S-ON
HBOOT-0.33.0012
MICROP0b15
TOUCH PANEL-SYNT0103
RADIO-4.06.00.12_7
Dec 17 2009, 13:05:23
ABOUT PHONE
Model number: Nexus One
Android version: 2.2
Baseband version: 32.36.00.28U_4.06.00.12_7
Kernel version: 2.6.32.9-27220-g328f560 [email protected] #1
Build number FRF50
Thanks in advance for any help/info!!

Looks like you still have the stock recovery image... do you have backup & restore options iin recovery mode, if not, you still have the stock recovery, reflash Amon-RAs recovery...

No, I don't have backup or restore in the options, neither in recovery or fastboot.
This doesn't make much sense. Here's what I'm doing. It looks like it should be working fine:
Code:
C:\Users\Chris\Desktop\meh\android-sdk-windows\tools>fastboot devices
HT9CWP806497 fastboot
C:\Users\Chris\Desktop\meh\android-sdk-windows\tools>fastboot.exe flash recovery
recovery-RA-nexus-v1.7.0.1.img
sending 'recovery' (3948 KB)... OKAY [ 0.582s]
writing 'recovery'... OKAY [ 1.439s]
finished. total time: 2.021s
Edit:
I was thinking maybe I need a different radio image, but then I remembered reading that Froyo came with a new radio image (right?). And I couldn't install a new radio image anyway because the update.zip files won't load. I'm pretty stumped here....
Edit again:
The code above was what I just did to flash the new recovery, and I still don't have the options to backup and restore the data.
Another edit!: I also loaded Modaco's superboot again (successfully) and started the process over again with no luck.

You don't have a backup/restore option with AmonRa's 1.7.0? That means you don't actually have the custom recovery. Your fastboot is lying to you.

In the terminal app,type "reboot recovery". What happens?

And,try dropping the ".exe" from fastboot.

what they said. Sounds like you still have the stock recovery image. Try reflashing the recovery again.

I tried both the regular RA recovery and RA Cyanogen recovery using both commands, fastboot and fastboot.exe but I continue to get the same recovery image.
I know there's no way to relock the bootloader, but is there any way to reverse what Modaco's superboot did and try that again?

Go here. Scroll to the bottom of the first post. Looks at the screenshots. Does your recovery look like that?

Nope, it's the stock recovery image with the exclamation point and Andy in the background. 4 options: reply, update.zip, factory reset, and wipe cache

Flawd said:
Nope, it's the stock recovery image with the exclamation point and Andy in the background. 4 options: reply, update.zip, factory reset, and wipe cache
Click to expand...
Click to collapse
Try using amon ra recovery image stock for n1, not the cyanogen version.
This one:
http://files.androidspin.com/downloads.php?dir=amon_ra/RECOVERY/&file=recovery-RA-nexus-v1.7.0.1.img
and rename it to recovery.img or something short then try the fastboot flash recovery recovery.img

Flawd said:
Nope, it's the stock recovery image with the exclamation point and Andy in the background. 4 options: reply, update.zip, factory reset, and wipe cache
Click to expand...
Click to collapse
Confirm you have root. Go to the terminal app and type "su". What does it say?

Well root isn't necessary to flash a recovery. He just needs an unlocked bootloader.
Well, OP, you might as well just find a different computer and try it on that.

FaJu said:
Well root isn't necessary to flash a recovery. He just needs an unlocked bootloader.
Well, OP, you might as well just find a different computer and try it on that.
Click to expand...
Click to collapse
OP said he unlocked the bootloader.... so OP verify that when you TURN ON your Nexus One, the logo with the X there is a PADLOCK on the bottom of the screen. If it does, then your bootloader is unlocked and you need to install amon ra recovery.
If no padlock, you're not unlocked.

OP make life easy. Go to Market. Install ROM manager. Either install clockwork recovery, or scroll down. Select the option to flash another recovery. Flash. Done

[Q] Nexus One dead, no screen Response

Hi everybody, I unlocked a N1 using fastboot and clockwork recovery. At the time to install the CM6 I encountered and error related to the version of de HBOOT.
I found a guide by Amritttt for reverting HBOOT to 0.33.0012, when I flashed PASSIMG following reboot the screen has become dead.
I tried to re-flash the phone with Amon_Ra recovery (1.8.1 and 2.0) but I can't enter in any mode. The only way I found is entering in the Bootloader and pushing files using fastboot... so I tried to restore the original system using the following:
PASSIMG_Passion_Google_WWE_1.01.1700.1_ERD79_release_signed
Passion-VF-FRF91
with this method: uncompress, flash userdata, system and recovery.
But it did't work, in the last flash the phone hasn't the SIM inside and I realized that the trackball blincked in red two or three minutes after rebooting. So I am wondering if I have a SLCD N1 what can I do to solve this disaster??
thanks!

Look at my signature, go there, see "Unroot/restore your Nexus", reflash EVERYTHING - either with fastboot (and you need to reflash HBOOT too), or do the PASSIMG method - with FRG33, and then upgrade to FRG83.

actually ignore me, that wont work for s-on, yeah, u gunna have to go through the pass-img method, completely reverting back to stock and start from scratch

Thanks, I'll try. I can't use PASSIMG method because my screen ism't working, or there's other way to do?
When you say all, you refer to use "fastboot flash all FRG33" Doing that I reflash alse the HBOOT or I need to do something more?
Thanks

ptrigomou said:
Thanks, I'll try. I can't use PASSIMG method because my screen ism't working, or there's other way to do?
When you say all, you refer to use "fastboot flash all FRG33" Doing that I reflash alse the HBOOT or I need to do something more?
Thanks
Click to expand...
Click to collapse
Can you not get your working hboot.img
boot to fastboot by Powering off
Power on by holding power & Trackball (will take you directly to fastboot)
then do "fastboot flash hboot hboot.img"

bagofcrap24 said:
Can you not get your working hboot.img
boot to fastboot by Powering off
Power on by holding power & Trackball (will take you directly to fastboot)
then do "fastboot flash hboot hboot.img"
Click to expand...
Click to collapse
The hboot files i have are hbootxxxxxxxxx.nb0, it's ok?

bagofcrap24 said:
actually ignore me, that wont work for s-on, yeah, u gunna have to go through the pass-img method, completely reverting back to stock and start from scratch
Click to expand...
Click to collapse
Yeah, but my screen is not working, and ADB is not reconizing the phone. I only can send files using fastboot and the screen is not working
There is a method for doing the pass-img method using fastboot?
or maybe the only problem is the HBOOT?

OK, here we go
Download Latest Amon-Ra
http://forum.xda-developers.com/showthread.php?t=611829
copy it to your android-sdk/tools/ folder and rename recovery.img
boot to fastboot, (Power & Trackball)
open up a shell (cmd prompt) and
cd (path to sdk/tools)
fastboot devices (make sure your device is there)
fastboot boot recovery.img
your phone should boot into recovery image
use your method for flashing through adb now if you can
if you can't then try flashing the korean wwe update
hit enable usb-ms
download this, its a korean FRF91 build. it is known to have the updated 0.35.0017 Hoot in it which i believe has support for slcd displays, http://forum.xda-developers.com/showthread.php?t=722281
copy to your SD
hit trackball to disable usb-ms, go to wipe, wipe all data
then goto flash image from zip,
choose the korean frf91 that you just downloaded hopefully when you reboot you will have updated your hboot again

i tried the baove method but i cannot get the recovery .......i have the same problem my display is dead !! i have gone into recovery but i cant see it and hence cant do a wipe and flash the zip can nyone please help me!!!!

Jack gave you the response you need.
Follow the unroot/restore guide from the wiki, using the PASSIMG method:
http://forum.xda-developers.com/wik...des_&_Tutorials#Unroot_.2F_Restore_your_Nexus
The long to the files is on the word "here" on step 2. Use FRG33.
This is done from the bootloader - you don't need to use recovery...
Sent from my Nexus One using XDA App

actualy i cant see anything cant see fastboot menu nor the bootloader! so i will not be able to do from step 2...please can nyone tell me wad to do?? is my fone bricked?? do i have to giv it to htc??

Its HBOOT, not recovery.

Rusty! said:
Its HBOOT, not recovery.
Click to expand...
Click to collapse
What's HBOOT, not recovery?
Sent from my Nexus One using XDA App

[Q] Is Fastboot the answer to my woes?

I want to flash a new radio and kernel to my G1 that is running CM6. My signal is atrocious and I get a few random oddities each day.
I have tried the recovery flash for the radio at least 6 times now in various ways following various guides and every time I do it it crashes my phone and I end up flashing the image, rooting, etc, to get back to CM6. it takes me over an hour to get back to normal and it just plain sucks!
So my question is..... Can I use fastboot flash to flash the image files for the radio and the kernel without being on the special Hboot 1.33.0013d and such?
I was planning to use the instructions from the ezterry kernel page and just want to check that I wont bork up my phone. I seem to recall that the fastboot flash bypasses all the need for FR-remove and such but want a second opinion before I take the dive this way.

Not trying to drive you away from CM 6, but have you tested other ROM to see if it has the same problem or similar.
I personally myself could not get CM6 to work properly on my G1 back when I was trying to use it.

I couldn't get the radio to recovery flash even on the stock ROM after rooting.
I guess I could try a different ROM.
I just now have proven to myself that i cant flash the EzTerry kernel from Rom Manager and clockwork recovery as I am in the midst of yet another image flash, re-root, and such after it wouldn't go past the reboot screen afterwards
This phone is just an extra toy but I am determined to figure it out.
I suppose I will just try the radio.img flash from fastboot tonight when I get home.
As long as I dont brick it I can always start over from scratch.

so I copied the image I want to flash onto the root of my sd card
did the camera+power boot
pressed the back key and I am at the screen with the red fastboot usb box
I plug into the computer (adb already installed and working fine) and go to the command prompt and type
fastboot flash hboot hboot-1.33.0013d.img
the screen says error: cannot load 'hboot-1.33.0013d.img'
Did I put the image file in the wrong place?
Edit: I put it in the root of the computers c: drive and typed
fastboot flash hboot c:\hboot-1.33.0013d.img
seems to have worked.

FireRaider said:
so I copied the image I want to flash onto the root of my sd card
did the camera+power boot
pressed the back key and I am at the screen with the red fastboot usb box
I plug into the computer (adb already installed and working fine) and go to the command prompt and type
fastboot flash hboot hboot-1.33.0013d.img
the screen says error: cannot load 'hboot-1.33.0013d.img'
Did I put the image file in the wrong place?
Edit: I put it in the root of the computers c: drive and typed
fastboot flash hboot c:\hboot-1.33.0013d.img
seems to have worked.
Click to expand...
Click to collapse
do the same thing with the radio and recovery

maximo360 said:
do the same thing with the radio and recovery
Click to expand...
Click to collapse
I got the recoveryand the hboot to flash but damned if I can get any radio to flash.
I get
writing 'radio'...
(bootloader) signature checking...
FAILED (remote: signature verify fail)
this is with both version of the radio downloaded from the links in the EzTerry thread
What in the world am I doing wrong that I cannot flash a new radio?

installed the spoofSPL... didnt help
edit: Started over again from scratch, rooted, flashed RA recovery, dangerSPL, then fastbooted and managed to install the hboot and the new radio. I guess CM6 hates the newer radios.
edit: Pretty sure CM6 does hate the radio because now its hung up on the install screen.
off to do more research.

People ... you should read before flashing around.
Ok, let me try to help.
1) As long as you have a fastboot enabled SPL, there is no need to 're-root'. Boot into hboot and flash the things you want.
2) Going to 1.33.0013d you *lose* most of your fastboot capabilities, e.g. flashing a new SPL/radio/recovery is no longer working. The only chance is to flash a signed nbh-file (e.g. fully signed rom)
I suggest you to read Terry' thread carefully (a link is in my signature) and then to retry ...
Btw: If you have installed the "new" radio/spl combo you need an adopted kernel, too, otherwise you will get bootloops.
Sent from my Gingerbread on Dream using XDA App

AndDiSa said:
People ... you should read before flashing around.
Ok, let me try to help.
1) As long as you have a fastboot enabled SPL, there is no need to 're-root'. Boot into hboot and flash the things you want.
2) Going to 1.33.0013d you *lose* most of your fastboot capabilities, e.g. flashing a new SPL/radio/recovery is no longer working. The only chance is to flash a signed nbh-file (e.g. fully signed rom)
I suggest you to read Terry' thread carefully (a link is in my signature) and then to retry ...
Btw: If you have installed the "new" radio/spl combo you need an adopted kernel, too, otherwise you will get bootloops.
Sent from my Gingerbread on Dream using XDA App
Click to expand...
Click to collapse
I managed to get everything work and am running CM6.1+2708 and 0013d with the .27 radio.
Why do we go to the 0013d if it screws up the fastboot? I notice in your signature you are running it also?
And say I want to flash a different rom now? I can only do it from RA recovery, Correct?
But as it stands now I ought to be able to experiment around with the other radio and other roms using recovery without any more issues? Or do they need to have certain parameters?

Once rooted, (to my knowledge) you do not required to re-root it again.
You can use RA Recovery to flash other ROMs with out having to re-root. (as to what I was told) And I recommend RA Recovery instead of ROM Manager/ClockMod Recovery (bad experience with it personnaly).
So as long as the ROM that you want to try is compatible with your current SPL/radio. You should be fine.

[Q] lost root after 2.3.6 update

hi there every one i updated my nexus one to 2.3.6 (GRK39F) from stock 2.3.4 (GRJ22) sorry but i did not read the post for to upgrade and keep root before upgrading to 2.3.6 and now i am suffering and thought it is not a good idea to post a question there so posting here
my problem is when i upgraded 2.3.6 i was rooted and had clockworkmod recovery image and i had a backup from rom manager as well but before upgrade i wiped the partition and cache and after upgrade i dont have SUPER USER permission nor the clockworkmod recovery tried to flash su.zip from sd card but no luck please can anyone help me get my root back pleaseeeee i need help ....

You'll have to passimg back to an earlier version of Froyo, root, restore your backup, and then flash the update and su zip...

danger-rat said:
You'll have to passimg back to an earlier version of Froyo, root, restore your backup, and then flash the update and su zip...
Click to expand...
Click to collapse
Thankyou very much danger-rat really appriciate your help but today was a bit lucky day for me
I tried to flash a recovery image through ADB and then it went well and then flashed the su.zip from sdcard that gave me superuser permission again thanks again for your help
@0mpranav

No need to flash the system partition, no need to use ADB, just flash Superboot:
Code:
https://bexton.net/2011/09/24/root-access-for-nexus-one-on-android-2-3-6-grk39f-superboot/

If your bootloader is unlocked all you have to do is reboot into fastboot mode. Flash a custom recovery such as RA or CWM, reboot directly into revovery and flash su.zip or whatever flash zip you used to root your device before. Reboot and you are rooted once again.
The following thread has a step by step how to do it. It's fast and easy.
http://forum.xda-developers.com/showthread.php?t=1019759

jboxer said:
If your bootloader is unlocked all you have to do is reboot into fastboot mode. Flash a custom recovery such as RA or CWM, reboot directly into revovery and flash su.zip or whatever flash zip you used to root your device before. Reboot and you are rooted once again.
The following thread has a step by step how to do it. It's fast and easy.
http://forum.xda-developers.com/showthread.php?t=1019759
Click to expand...
Click to collapse
Yup. This is the way every one should be doing it. It's sort of the whole point of the Nexus One. It has an unlockable bootloader.

GldRush98 said:
Yup. This is the way every one should be doing it. It's sort of the whole point of the Nexus One. It has an unlockable bootloader.
Click to expand...
Click to collapse
I have purchased two second hand Nexus Ones. The first thing I did after receiving them and charging the battery was to reboot into fastboot mode and issue "fastboot oem unlock" command. Since they were purchased second hadn I didn't thing I had a warranty anyway so unlocking the bootloader seemed to be a non brainer.

GldRush98 said:
Yup. This is the way every one should be doing it. It's sort of the whole point of the Nexus One. It has an unlockable bootloader.
Click to expand...
Click to collapse
Will any version of su.zip, and fastbook.zip work? What about recovery-RA-passion-v2.2.1.img? or should we be using a different version?
If we should be using different versions of those, could you link to where we could get them?
I've had my Nexus one half-rooted since 2.3 came out, and I haven't been able to root it back.

why mess with 2.3.6 just use oxygen 2.3.7...

kuljit55 said:
why mess with 2.3.6 just use oxygen 2.3.7...
Click to expand...
Click to collapse
I'm sorry I have no idea what that is. I don't even know if its helpful at all. Again, I don't even have root, or a custom recovery. Presently, I have an unlocked bootloader, ADB on my PC, and a half-rooted nexus one from before 2.3.
I have absolutely no idea how to do anything presently, and when someone tells me that trying to root on 2.3.6 is futile and to just use a custom update, it doesn't make any more sense to me.
Care to elaborate past one line that doesn't help at all? Hell when using shell commands through adb, it keeps on saying "permission denied" any time I type in su.

You have an unlocked bootloader, so flash a custom recovery via fastboot, and use the custom recovery to flash the su zip...

danger-rat said:
You have an unlocked bootloader, so flash a custom recovery via fastboot, and use the custom recovery to flash the su zip...
Click to expand...
Click to collapse
Thanks Danger-rat. Although I know you said nothing different that what was already said in this thread, I figured that since you didn't give me specific info about whether or not there were multiple versions of su.zip or fastboot.zip, I figured I should take that as a "No.", so I went for it. All re-rooted now.
I appreciate the help.
EDIT: So if you are as new to this stuff as I am, anyone else who's reading-
You can DL su.zip from http://www.google.com/url?sa=t&sour...ZxOuf9Kw_URvtvh9Q&sig2=Hj72LDNoiBq2Zoa4QquZWQ
and fastboot.zip from http://www.mediafire.com/?ttdkgamud3j
and amon Ra 2.2.1 from http://files.androidspin.com/downloads.php?dir=amon_ra/RECOVERY/&file=recovery-RA-passion-v2.2.1.img
then follow the directions here: http://forum.xda-developers.com/showthread.php?t=1019759
** Note: again, these are for people who have unlocked bootloaders. For that info, you'll have to go elsewhere, but it should be readily available, such as this stuff is. I'm just linking it again because I know how frustrating it can be for people like me who aren't too well versed in rooting/unlocking yet.

Downgrade 2.3.6 to 2.2.2 - Nexus One
Problem:
I would like to downgrade my Nexus One to 2.2.2, because I've had non-stop problems with Gingerbread.
So I've gone through the Bootloader -> Recovery -> apply sdcard:update.zip steps, and it fails. This begs the question, how do I go from 2.3.6 to 2.2.2?
Fix:
Generally, phone manufacturers will not allow you to downgrade for various reasons. The stock recovery does indeed validate the update image, so that it's of a greater (or same) version than the installed system. With the Nexus One being a developer phone, you can unlock the bootloader and replace the recovery image with the one that doesn't perform this check, and will allow installation of any image. The caveat is that unlocking the bootloader voids your warranty with the carrier (and sometimes the manufacturer too,) and wipes all user data off the device.
Unlocking the N1 is dead easy. Just install Android SDK and the USB drivers (located in "google-usb_driver" directory.) Then restart the phone in bootloader mode by shutting it off and powering on while holding down the trackball, hook it up to the computer via USB, and in command prompt issue the following command: C:\<path to Android SDK>\tools\fastboot oem unlock. You will be presented with a confirmation screen with further instructions. Upon successful unlock, you can flash a custom recovery that will allow you to install any custom ROM, including downgrade to 2.2.x stock version of Android OS.
To flash ClockworkMod recovery, download the latest version for Nexus One from here, reboot into bootloader mode (power on while holding the trackball down,) and in command prompt issue command C:\<path to ANdroid SDK>\tools\fastboot flash recovery C:\<path to downloaded img>\recovery-clockwork-3.0.0.5-passion.img
Reboot to bootloader mode again, and then use the Volume keys to highlight the "Recovery" option and press Power button. You are now in ClockworkMod recovery, and can flash any custom ROMs via the "Install zip from sdcard" option.
Here is a "stock" 2.2.2 ROM (with root) off XDA-developers forum.
http://forum.xda-developers.com/showthread.php?t=927935
source:http://android.stackexchange.com/questions/13933/downgrade-2-3-6-to-2-2-2-nexus-one
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