Download the kernel update from here.

If you’re running on a user you should try to install like default installation.

Fix Nexus One problem

Step 1: First run a userdebug or eng build. This update won’t run on the user build, you will get verification failed;
Step 2: Download the update from here;
Step 3: Now you should copy the file to phone SD cars, but first rename the file into update.zip;
Step 4: In case that you have adb, try adb reboot recovery(more details for abd here);
Step 5: If you don’t have adb try the next steps:

• Power off your phone
• Turn it on whilst holding the trackball down
• At the boot screen, use the volume keys to select bootloader then press the power button to select
• At the next screen, select recovery and press the power button to select it
  

Step 6: The boot cross will appear, and shortly after a ‘!’ graphic will appear. Hold down the power button, then press volume up;
Step 7: You will see a menu with blue text. Use the trackball to highlight and select apply SD card update;
Step 8: The process should take a few seconds, after which you can reboot your phone;
Step 9: If you get verification failed you probably have a user build;
Step 10: You now have a tether-enabled kernel.

Next you can read the instructions for user build: All steps before step 12 are safe and wont touch your phone’s Rom /flash

Step 1: Get a copy of adb and fastboot (check the SDK or Google for them);
Step 2: Grab the Nexus One update zip and nexusone-zimage from the downloads page;
Step 3: Plug your phone’s USB in;
Step 4: adb reboot bootloader;
Step 5: When the bootloader screen appears: fastboot boot nexusone-zimage;
Step 6: Make sure the phone boots, if not, STOP

• Note that Wifi will not work at this stage.
• If the phone fails to boot, something is wrong. Pull the battery to reboot.

Step 7: Unzip the update zipfile, then adb push bcm4329.ko /sqlite_stmt_journals/;
Step 8: adb shell;
Step 9: su;
Step 10: insmod /sqlite_stmt_journals/bcm4329.ko;

• If an error appears doing this, STOP;

Step 11:  lsmod;

• You should see ‘bcm4329′ listed. If not, STOP;

Step 12: mount -w -o remount /dev/block/mtdblock3 /system;
Step 13: cat /sqlite_stmt_journals/bcm4329.ko > /system/lib/modules/bcm4329.ko;
Step 14: Logout out of the phone;
Step 15: adb reboot bootloader;
Step 16: When the boot screen appears: fastboot flash zimage nexusone-zimage;
Step 17: fastboot reboot;
Step 18. Your Nexus One should come up;

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