adb push and mount problems I'm using Android 2.3.3 and I want to copy the iwconfig file to /system/xbin.
First I tried doing it with adb push using this:

adb push iwconfig /system/xbin

But in return I had: failed to copy 'iwconfig' to '/system/xbin/iwconfig': Permission denied

So I made my research and finally found this mount command that actually worked (most of them returned the usage: mount []... line)

mount -o remount,rw /dev/block/mtdblock4 /system

But even with that I'm still having the "Permission denied" line.

I also tried
mount -o remount,rw /dev/block/mtdblock4 /system/xbin

Buth it returned "Invalid Argument"

Any ideas?
First, make sure adbd is running as root:

adb root

If you get an error that says something like "unable to run as root on production builds" it means that you must always issue su command in the adb shell to gain superuser privileges.  You will need to enter the shell before any mount commands will work.  You will need to push the file to the SD Card, then mount /system partition as read-write, and then copy the file to the /xbin directory like so:

adb push [path-to-iwconfig] /sdcard/
adb shell
su
mount -o remount,rw /system
cp /sdcard/iwconfig /system/xbin/
mount -o remount,ro /system
exit
exit