error: device unauthorized. Please check the confirmation dialog on your device.

While encountering this error in linux shell, you could fix it by applying below instruction

•  unplug your device
• (in shell) SDK_DIR=(android_sdk_directory)
• cd $SDK_DIR/platform_tools
• ./adb start-server
• plug device
• confirm authorization

Convert pdf to image in linux

If you look for a tool in order to convert a pdf document to a image, you could use a useful command:

convert document.pdf document.png

this little tool come in handy very much.