Over the years of owning various Android devices, one thing has regularly been a pain for me: syncing my music library to my phone. Ever since Android made the switch from Mass Storage to MTP (Media Transfer Protocol), things have been really rough. On most of the Linux distros I’ve used, the support for MTP devices was pretty bad. To sync, I wrote a rather complicated script to mount the device using go-mtpfs, check that things were sane, then rsync them over. The results ranged anywhere from slow to buggy to completely unusable. When I got my shiny OnePlus One in the middle of last year, it got so bad that I was getting entirely different results using the same software on the same distro between my desktop and my laptop. I ended up going months with my phone library out of date.

It was around then I began to consider going over the network, since other than MTP I really didn’t have a good option besides maybe hacking something together with ADB (ew). Desktop and laptop were syncing fine over Syncthing, which is a really cool project that I recommend you check out. Unfortunately, Syncthing on Android was also slightly buggy for me, due to some know issues with Android and having access to file modification times. I was already using rsync before, and I knew rsync could work over the network. Why not see if I could do that with Android as the target?

The answer I found was a (free and open source!) app in the Google Play store called SSHelper. SSHelper runs an SSH server on your device and through that can do things like transfer files and run rsync. I was amazed when I actually tried it out: rsync over the network was running faster than over USB. A really cool benefit of doing it this way versus with an MTP FUSE module is that since rsync is running locally on the phone, it can do things like look at timestamps or compute checksums on its own, without the file being transfered. With the USB setup, the file has to be read in order to learn these things, which brings it over the cable (slowly, in my experience). This is important since rsync does a lot of checking of what’s already present in the target in order to determine which files to update. This is such a significant speedup for me that it runs about twice as fast over the network versus USB, even though intuition would say that a physical connection should be faster.

TL;DR:

The process is relatively straightforward:

  1. Install and run SSHelper. It’ll generate SSH keys at first, just let it finish. It’ll automatically start the SSH server listening on port 2222.
  2. It is highly recommended to change the default password, since it defaults to “admin”. This means anyone on your local network can see the contents of your phone’s storage until you change this. Click the wrench tab at the top to adjust the password and other settings. This will also show your phone’s IP address.

  3. Once you’ve set a new password and know your phone’s IP address, the command you’re probably looking for is:

    rsync -rdv --delete-after --size-only /home/{you}/Music {phone ip}:SDCard/ -e 'ssh -p 2222'

    This assumes that your phone’s music is stored in SDCard/Music and your computer has it stored in /home/your-user/Music. If you need to change these be careful! Rsync is very sensitive about things like trailing slashes. If you want to exclude some folders (Like .stversions, for Syncthing users), you can add --exclude=.stversions. Excludes are done relative to the source path.

  4. When you’re done, click the dots in the top right and select ‘Stop Server & Quit’. No sense running the server and wasting battery or risking having someone SSH into your phone when you’re out and about.

With this setup the command to sync is simpler than my old hacked together script, it runs faster, and it avoids buggy MTP implementations.

I tend to be pretty passionate (read: opinionated) about how I organize and store my music library, so I might write some more posts about it in the future. I really would like to put my thoughts out there about managing a hybrid lossy/lossless library.