Adb push does not work When I run the command

adb push file.txt /flash/Data


it writes this error message

failed to copy 'file.txt' to '/flash/Data': Read-only file system


I tried to solve it according to this page
http://android-tricks.blogspot.com/2009/01/mount-filesystem-read-write.html but with no success.

Could you navigate me and solve the problem? thank you
You have to have root access to mount the drive as that article is describing (calling su == becoming root).

What are you trying to accomplish? Can you push the file to the sdcard instead (if your device has one)?