How to sync SD Card to Android folder

I’m feeling like an idiot and have already spent a considerable amount of time reading posts here and elsewhere trying to find an answer. I’ve been using Syncthing for several years to sync lots of stuff between my phone, PC and Unraid server.

I want to sync an SD card to a folder on my Android device. This SD card comes from my CPAP (device for sleep apnea). I want to be able to plug the SD card into my phone in the morning and have it sync the data to a folder on my phone.

I managed to add the SD card as a folder in the Syncthing Android app (F-Droid v 1.27.6), though I get a Filesystem Watcher error. Right now it says “error while traversing /storage/0A1F-9247/Android/data/com.google.android.apps.maps: no such file or directory.” I’m assuming my phone is adding these app directories to the SD card. If I delete the directory with the error it just errors on a different directory.

My biggest confusion, though, is how to setup the sync. How do I tell Syncthing to sync that SD card to a specific directory on my phone? I was thinking maybe I need to add my phone as a Device and then share the SD Card folder to it, but can’t find a way to do that.

Syncthing doesn’t do local sync. It works between an arbitrary number of connected devices, but not between folders on the same device. It’s just not what it was designed to do. You will probably find a better solution for this sync with a different app.

Thanks for the reply. So am I misunderstanding what users like this are doing? I’ve read several posts where it seems like users are syncing with an SD card on their phone.

It might help to think of it like this – a minimum of two instances of Syncthing are required for a successful sync. A typical setup could be a pair of computers, a computer and a phone/tablet, a computer and a NAS, etc. It’s also possible to run two Syncthing instances on the same computer to sync files between users and/or between storage devices.

Yes, but those users are talking about syncing files from a computer or different phone to the SD card on another phone (if you count up the number of Syncthing instances, there are at least two).

For your particular use case, if you want to use Syncthing, the simplest option is to plug your CPAP’s SD card into your PC or Unraid server and share that Syncthing folder with your phone. Caveat is that you’ll have to work out the logistics of syncing a storage device that isn’t always plugged in.

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Got! Thanks for taking the time to lay it out for me. I now see that I was failing to understand that they’re syncing to a different device.