[Nexus S Q&A, Help & Troubleshooting] xdart:
UPDATE#2: Ok, so it seems the red triangle+bugdroid has something to do with the recovery image being hosed. There is also a file named /system/recovery-from-boot.p which needs to be renamed PRIOR to flashing with CWM, or CWM will not "stick" and the red triangle+bugdroid will keep coming up.

In order to rename it, you have to remount /system as read-write. After renaming the file to /system/recovery-from-boot.p.bac I rebooted into recovery and re-flashed CWM with fastboot, only this time I flashed in CWM 6.0.1.0 instead of the recovery image from the One-Click-Nexus-S-4G file. After wiping cache, dalvik cache, data and factory reset (from CWM) I selected "reboot system now" and was presented with and option to "YES - Disable recovery flash". This option apparently fixes the hosed recovery issue somehow (maybe renaming /system/recovery-from-boot.p ?) so I selected YES and rebooted. rebooting into recovery seems to work OK now with no red triangle.

UPDATE #1: I tried rebooting into recovery a few hours later and just get a screen with a green droid+red triangle icon. Um any ideas where CWM went?

Thanks for the info. I just got my D720 rooted in Linux with the commands below. Maybe it will be of help when you switch.

I am kind of picky about verifying md5sums. I like to be able to make sure they downloaded correctly/haven't been altered. I wasn't able to google the md5sum (c4cecfc494610d6c0f13b2237bd212a0) for root.zip in the One-Click-Nexus-S-4G file. Hard to say why it's not out there, but I opted instead for Superuser-3.1.3-arm-signed.zip from androidsu.com.

files used:

recovery.img (from the One Click..) - md5sum - 5988836a66f535c4a7d499ee417ee9c5

Superuser-3.1.3-arm-signed.zip renamed to root.zip - md5sum - b3c89f46f014c9df7d23b94d37386b8a

unlock phone (!!! wipes it !!!)

need to enable settings > applications > developer options > select "USB debugging" or adb won't see it

# adb devices (should show your device. if not adb kill-server; adb start-server and try again)

# adb reboot-bootloader

# fastboot oem unlock

# fastboot reboot

** Phone took longer than normal to reboot after this.

After rebooting

# adb reboot-bootloader

# fastboot flash recovery recovery.img << from One-Click-Nexus-S-4G

- use volume-down, select recovery and press power

- go to the mounts and storage menu

- if it says "unmount /sdcard" then you do not need to follow this step)

- if it says "mount /sdcard", then select it.

- select "+++++ Go Back +++++"

push root.zip to phone and install it

# adb push root.zip /sdcard/

- Select "install zip" from sd card

- Select "choose zip" from sdcard

- Scroll all the way down and select root.zip

- choose yes

- select "+++++ Go Back +++++"

- select "Reboot System now"

After rebooting, I found the SuperUser icon was indeed in able to su to root

# adb -s 416321DE1F8100FD shell

shell@android:/ $ su -

root@android:/ #

UPDATE - Red Triangle + Bugdroid Fix

Login to the device and su to root. All the commands starting with 'su -' up to 'exit' are done on the device and NOT the host OS.

# adb shell

$ su -

# cd /system

# mount -o remount,rw /system

# mv recovery-from-boot.p recovery-from-boot.p.bac

# mount -o remount,ro /system

# exit

Reboot the device into recovery mode using volume+power, or adb reboot recovery

(These commands are done from the host, just for clarification)

# fastboot flash recovery /tmp/recovery-clockwork-6.0.1.0-crespo4g.img

After that, select recovery from the menu and you should get CWM 6.0.1.0 where you can do a backup or whatever.