Re-rooting a UK Vodafone HTC Magic following Android 2.2.1 update

I have been running various versions of CyanogenMod on my HTC Magic for a long time now. Ever since I decided that Vodafone were never going to bother to release any updates after the Donut (Android 1.6) update. However, I recently noticed that in December 2010 they finally release an update to upgrade these phones to Android 2.2.1 (FroYo). The files for this can be downloaded from Google's servers just like the last OTA update. This time there are two files - one to update the bootloader and one for the operating system update.

Before going any further I'll just point out that when I started this the fastboot screen reports the following settings and the final settings after completing the update in column 2:

Official OTA updates are written to expect a known configuration as a starting point. So if we want to use this it is time to revert back to the original image shipped with this phone. Fortunately I have my nandroid backup from the 1.5 days, so using the Amon RA recovery image I have installed as part of the CyanogenMod ROM I can revert back and begin applying first the update to Donut and then the new one to FroYo. Part of the reason for this is that the lastest update includes a new radio image which apparently leaves a bit more RAM available for the running system. As memory contention is the most significant problem with the HTC Magic, this has to be good. We shall see.

I downloaded 3 update files. The update from Cupcake to Donut, the bootloader update and the update from Donut to FroYo. Each file in turn needs to be copied to the sdcard and called update.zip. (adb push filename /sdcard/update.zip). Then reboot the phone holding down the Home key to restart in recovery mode. Once the recovery image is shown, pressing Home and Power shows a menu and you can select apply update.zip to flash the image. The hboot image looks quite scary as it works - it reboots the phone 3 times but eventually boots the operating system once again. Just wait for it patiently.

So now I have the official Vodafone released Android 2.2.1. So lets see about making a backup. Boot the phone to fastboot mode and try running the Amon RA recovery image: fastboot boot recovery-RA-sapphire-1.7.0G.img. Access denied. I had a suspicion this might happen given the bootloader update. This is a shame but not really a problem. We can use various rooting methods but I simply copied psneuter to /data/local/tmp and ran that from an adb shell. With that done I have a root shell and can remount the system partition readwrite and copy su, buzybox and the Superuser.apk file from my CyanogenMod build tree. This fixes root access.

Completing the job requires changing the recovery image so that I can boot that and make complete nandroid backups. The Vodafone release includes a script that checks for a valid image in the recovery partition and replaces it if it no longer matches the known version. This script is in /etc/install-recovery.sh and this is called from the Android init process. It updates the recovery partition by patching a copy of the boot partition using the binary patch file in /system/recovery-from-boot.p. So to make our recovery stick around we need to rename the install-recovery.sh script and the /system/recovery-from-boot.p files and place our own copy of Amon-RA 1.7.0G at /system/recovery.img. Then we can flash this using flash_image recovery /system/recovery.img.

The reason Vodafone use a patch file is to keep the size of the recovery copy small. Possibly we could so the same thing however I used the imgdiff program from the Android build to generate a patch to from the current boot image to the new recovery image but it just makes a patch containing the whole image. Clearly there is insufficient commonality between the two to make this worthwhile.

Now at last I can make a nandroid backup of the updated system by booting to the new recovery screen. And I've got root access for anything that might require it. And after all this: Was it worth it? Actually yes. The phone seems to be running more smoothly with this over CyanogenMod 6. Watching logcat there are less messages about processes being killed due to low memory. So far it does appear to be worth doing. But I'm noticing all sorts of little CyanogenMod tweaks that are no loger with me. So how long it will stay this way I'm not sure.