Q:

Adb error: device not found while device is connected

I'm compiling and installing Android apps using command line and this is what happens when I'm trying to install it on a device:
$> adb devices  
List of devices attached  
8c092420    device  
$> adb install TestApp.apk  
error: device not found  
- waiting for device -

There is no problem when I use adb -s 8c092420 install TestApp.apk.
I would like to make some aliases for Linux bash (when I have to do something with a device without copying the device ID as I use several of them), could you please give me an advice how to make this working? Or what may be wrong?

A:

Problem solved.
It was because of the environmental variable ANDROID_SERIAL was set to an old device.
Use the next command if that happens to you too on linux/unix.
unset ANDROID_SERIAL

