Explained in simple steps:
1. You need ADB (Android Bridge) tools. Just paste this in your terminal as SU bash <(curl https://raw.githubusercontent.com/…/nexus…/master/install.sh)
2. The nexus tool downloads and install appropriate version of ADB for your Linux box. Wait few minutes.
3. As SU, execute => adb start-server
4. Enable USB debugging on ur RedMe and connect to your linux box.
5. Still as SU, execute => adb devices. It shall list your android device.
6. If you get “????????? no permission” as output from step 5, then you have not started adb service as SU and other commands too.
7. Once you got things straight. Now copy files from phone to pc via “adb pull” or paste to phone via “adb push”.
8. In my case, i wanted to copy entire DIR onto phone. So i did just “adb push /PC_DIR_Path/DIR_TO_COPY /PHONE/DIR_COPIED
9. To know the path on your phone, just use any file explorer and get the details of path. In my case it was /storage/sdcard1/Music. It could be different on yours.