All rooting methods fail. Direct write fails because there is no su, and update.zip fails because of invalid signature. For each one. I am running ICS on the SSG2.
If there is no su command, well, are you really rooted? Can’t you test https://play.google.com/store/apps/details?id=de.bwulfert.suchecker&feature=also_installed or https://play.google.com/store/apps/details?id=com.island51.gotroot&feature=search_result and check if you’re really root?
Well, I’ve bought this phone, it’s not locked by operator. I am not sure how to “gain root” while installing your software. The “direct write” method fails with error “su: file or path not found”, so I assume that there is no “su” binary on this phone. Any instructions on how to correctly start the installation?
EDIT: I tried with this as well, it is Edify, Binary 2. http://cmouse.fi/UPDATE.zip
SU Checker says:
Got 'su ?
Unknown
Status: su declined | not found
your device seems not to be rooted, because the su executable is missing. without it it will not work.
Ok. How about the firmware update then? It keeps whining about signature check failure no matter which option I choose.
you mean UPDATE.ZIP? This will work only on >> custom << recovery ROM (like CyanogenMod Recovery)!
So. How am I supposed to install the stuff rooted on the phone if I am using stock phone? Do I need to root it myself first or?
there is no root installation on stock phone (obviously) 
yes you need to root it first! (except you maybe have an unlocked bootloader. using the unlocked bootloader you can apply a custom recovery ROM without rooting).
Ok. I doubt that I have unlocked boot loader, since it requires signatures, but I’ll see if I can root the phone.
bootloader and recovery ROM are different things.
Yes, I can see now… I’ll see if I can get it rooted somehow.
Ok. Rooted with CWM and was able to use Direct Write method for avast!. Thanks