I tried and it kept bootlooping and I was almost panicking, but thankfully I managed to adb the original back!
Interestingly, I can't use adb push anymore, even though I have root :/
I think you need the Insecure ADB to get this working on KE2 (and possibly KE1) phones.
Paul has details here http://android.modac...ple-to-use-apk/
He's twittered that it should work on the SGSII but I haven't tried it yet.
Alternatively I think you could use ODIN to apply the Insecure KDD kernel again, make the changes than flash back the stock KE2 kernel ?
-- Edit --
I've found an alternative method over on XDA that is similar to Paul's method but just changes the directory file permissions that we need rather than modifying adbd etc.
mount -o rw,remount -t yaffs2 /dev/block/mtdblock3 /system
chmod 777 /system/app
chmod 777 /system/framework
That should set the permissions to allow you to write the file and you can set it back once you are finished by doing exactly the same thing except use
chmod 755 instead of 777.
You can use the command
stat -c '%A %a %n' /system/*
in the shell to check the values.
Edited by Matchstick, 16 May 2011 - 10:08 AM.