Try all these:
- confirm that you get adb version by typing adb version in console. If working check the adb which is running is from
which adbfor this.
- Check AVD manager and check that android tools are installed.
- Check that adb wasn't installed by other user.
- Install IA32 if you are using 64 bit architecture.
- Check permission for android sdk folder. if not give
chmod -R 777 platform-toochmod -R 777 platform-toolsls.
- Check platform-tools folder is added to your path.
adb kill-server adb start-server adb devices