Permission denied on /system/xbin/su when trying to unroot Sony Xperia L I'm trying to root my Sony XPeria L reading this tutorial The firmaware is 15.0.А.2.17, model C2105, and my Android version est 4.1.2

Everything was good until step 9, where I get the following error :
/system/bin/sh: /system/xbin/su: Permission denied

So I ran adb.exe from my computer and try to grant my permissions on this file. I tried some chmod 777 su but this is a "Read-only file system"...

I'm a C# developper and I always used Windows, so Android world is totally new for me. Can anyone help me to avoid this error message ?

Thanks you !
You have to remount read-only partitions with a permission of read and write first.

# mount -o rw,remount /
# mount -o rw,remount /system


Now, you can do anything.