Rsync on an Android phone

Every once in a while, there are some files that I want kept in sync between my Android-based phone and one of my Linux (or Mac, or any Unix, or maybe Windows too, but I use Linux…) boxes. Yeah, I can copy them over manually via USB or even something a bit simpler like AndFTP (assuming you can SCP to the target machine). But that’s a real pain for anything like my KeePass (well, actually KeePassX and KeePassDroid) password database, that I might add something to at any time and forget to sync. I also try to occasionally (waiting in line?) backup SMS, call logs, etc. on my phone, and like to have those synced back to the desktop automatically.

Enter the solution: rsync backup for Android, a rsync client for Android that includes Tasker plugins (there are a few things about the app that I don’t like, but it seems to be the only option at the moment), and Tasker, an automation framework for Android.Tasker is one of the few Android apps that I’ve actually bought (i.e. not free/no-cost), and is currently selling for $6.49. It’s an incredibly capable task automator, very much akin to Locale on steroids. On the down side, Tasker can eat up battery life if you don’t configure it intelligently, and it’s not always 100% reliable when interacting with the system. On the positive side, Tasker can identify practically any combination of states in the android system (from hardware and software events to GPS location, time, signal status, etc.) and perform almost any task on the system based on this information. Sure, this specific problem could be solved with a cron replacement (which Android lacks, of course), but Tasker can do things like play specific audio files when you get an SMS from a specific number, mute audio at certain GPS locations, or turn WiFi on when I get home and off when I leave the house. It also has a plugin architecture, and rsync backup for Android happens to have a plugin that works with it.

So, our goal is to have a daily, bi-directional, newest-file-wins sync between a directory on our Android phone and a directory on a computer. I’m not going to go into a lot of the computer-side stuff, mainly because that varies quite a bit between operating systems, and also because my personal setup is a bit paranoid in terms of security. For the computer side, we’ll need a machine that can be SSHed to from the Internet (either a static IP or a known hostname/dynamic DNS), a user that can run rsync over SSH, and a directory that’s writable (obviously).

Setup:

1. Buy and install the Tasker app.
2. Install the rsync backup for Android app.
3. Configure the rsync stuff on the computer. In the simplest form, we’ll just need a user that can login and run rsync, and a directory to sync from/to (note: this should be a directory used only for syncing the phone…).
4. Open the rsync backup for Android app. Use Menu -> Generate Keys to generate a new pair of SSH keys, and then get the public key setup on the target computer. See the developer’s web site for instructions.
5. Once keys are setup, create a new profile called “PC-droid”. Set the local directory to a new empty directory (I used /sdcard/sync), enter the remote host address, port, username, and remote directory, and select the private SSH key that you created. Check off “rsync on reverse direction”. As this program is just a GUI wrapper around normal rsync binaries, you can specify additional options to the rsync command; my string ended up being -vHrltDuO --chmod=Du+rwx,go-rwx,Fu+rw,go-rw --no-perms. If it helps, at the bottom of the screen you can see the actual rsync command line that will be run. Save when done.
6. Save the profile, then long-press it and select “Duplicate”. Change the name to “droid-PC”, uncheck “rsync in reverse direction”, and change your additional options as needed (mine became -vHrltDu --chmod=Dug+rwx,o-rwx,Fug+rw,o-rw --no-perms). Save when done.
7. Create a test file in the sync directory on the PC, and a different one in the sync directory on the droid.
8. One at a time, in the rsync backup app, tap on the profile names. If all goes well, the syncs should run, and both files will now be in both places. If there are any problems, the output should help; the most likely issues are probably permissions, rsync command options, or SSH keys.
9. Long-press each profile, select “Edit”, and check off “Close log window after job is done”. Save profile.
10. Now fire up Tasker. Click the “+” at the bottom of the screen to create a new profile, call it “sync”, and click the check mark.
11. On the First Context panel, tap Time, and select when you want the jobs to run; I chose 03:01. Tap the check mark.
12. On the Task Selection panel, tap New Task. Give it a name, like “sync2”.
13. On the Task Edit panel, tap the “+” button at the bottom left, tap Plugin, tap “rsync backup for Android”, click the “Edit” button on the Configuration line, and select the PC-droid rsync profile. Tap the check mark in the lower left to save.
14. Repeat the last step for the droid-PC rsync profile.
15. Tap the check box in the lower left. This saves the profile.
16. In the main Tasker screen, make sure there’s a green check to the right of the profile you just added, and that the button at the bottom right of the screen is set to “On”.

Assuming this all went well, the next time the time you specified rolls around, your sync should run. If you gave the task a name in step 12, you can setup additional profiles to run it at other times (or use the repeat logic builtin).