Synchro behavior if both synchro folder contains files at first start of synchro


I have a 2000 photos/video folder to synchronize on my Nas from my phone.

I want to save time so I want to initialize Nas folder with a lof of files already synchronized some weeks ago.

If I create the bidir synchronization from my android app to the folder that contains some photo on my Nas, what will happen:

  • a diff between files will be done and only new photos from my phone will be copied to the Nas ?

  • same but new photo from my phone will be removed ???

  • nothing: the sync will fail

  • a mix : recent files from the Nas will be copied and replace photo from the phone, recent files from the phone will replace photo from the Nas.

Thanks for your help

Same files will be shown as already in sync. Differing files with the same name will result in a conflict file being created (available on both sides). Metadata changes only such as permissions or file modification time will be resolved automatically as far as I remember. Files present only on one side will get synced to the other. Nothing will be deleted during first sync when starting with newly configured shared folders.

Thanks. Do you know if the tool is able to work in manual mode like sync back for instance:

Synchro is off Big modif are done : move files into folder etc. Launch a manual synchro and wait for status before authorize the synchro.

This would be cool be useful to check if synchro will be ok when modif are quite huge.

That’s not how Syncthing works. It’s a continuous file synchronization program.

If you can get it to work on the NAS, the Unison tool might be better suited for your needs, especially when only two devices are involved.

Thank. I did a first try with my folder with 2000 files. I paused directly the sync that was in scanning mode because the number of file analyzed with upper 2000, I don’t know why.

Also in recent change I don’t know why synthing display a lot of files (photo) that are identical to the one on my phone. (Because they came from my phone).

For me the two for were identical and the tool want to synchronize a lot of stuff. Very strange.

Where can I see some detailled log file ?

That’s the thing: Syncthing sees two files on either end. Without being able to sync/exchange metadata, they can’t know that the other has the same file - so ab initio both have files that are missing on the other. Once you unpause the connection, they’ll exchange the metadata and check that they are the same, which will show as “preparing to sync”.

You can get sort of such a manual intervention on first setup: Set both folders to type send-only. That means no change from the other device will be synced. If there are any difference, both devices will offer to override the other (don’t!) and show a list of differing files. Once you think those make sense, set the folders back to send-receive and the process that was already explained above will happen.

Ok thanks for explanation.

There is still a problem.

I don’t understand the number of files and folders indicated by the web gui interface (local state and global state)

For my SD card synchro number of folder and files are too high.

For my little test (synchro was ok) there were correct first but now number displayed are wrong also : 56 files and 24 folders. Whereas there is only one folder, the one I want to synchronize + .st_folder and 30 files.

This also scares me, what if the tool look inside wrong folders (but the little test was a success) ?

And finally I thought that web interface from the android app was the same interface than the web interface that I can reach to the Nas from my computer but no, there two different interface and I don’t understand well the differences between these two interface that look so similar.

I assume you mean the app interface here, right? It’s indeed very different than the normal Web GUI and much more limited. If you want to access the normal Web GUI on Android, there is a button to open it in the left slide-out menu in the app.

No I am speaking about web interface from the app.

This web interface don’t display same stuff than the ‘real’ web interface that I can reach from a browser.

For instance on the Web interface of the app, both synchro are paused

On the real web interface, one folder is paused, the other don’t.

What do you mean by “real” web interface? Do you mean the one that you access from the NAS, or do you access the Android interface remotely? Pausing folders is device-specific, so you can pause it on one end, and leave it unpaused on the other end.

Some screenshots of the interface would probably be helpful to make things clear here.

I think maybe there is a misunderstanding about the Web GUI. There is not one, central GUI to manage Syncthing. It is a distributed system where each device runs its own instance of the program. You are definitely looking at two different Web GUIs on the phone and the NAS. They can definitely show different states. For synchronization to happen, you need to unpause the folders on both devices.

Real web interface = interface accessed using a browser and :

App web interface = same interface accessed from android app

I have the feeling now that both interface don’t control same things.

Each interface control folder from different devices.

One interface for the Nas folders configuration Android app web interface for the configuration of folder for the phone.

Right ?

Yesterday I thought it was the same interface and that they control same stuff.

So there is not a central ‘configuration’ for instance if I want to pause the synchro I need to pause both on android app and also on the Nas ? Right ?

Regarding the file and folder number that is incorrect do you have an explanation or a log file that I can read to check what is the list of files and folder that are counted here ? Maybe the tool read a wrong folder ?

Ps:I can’t write too much as I’m a new user. I need to wait 1 hour between each post

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Yes, I think you got it now. Consider that an arbitrary number of Syncthing instances can participate in a shared folder, so each instance has control over their own view of the world, but not over others. If the configuration were centralized, anyone could for example stop others’ Syncthings from synchronizing, which would not be desired. As long as you have only two devices connected, pausing one side is enough.

I don’t know what you mean regarding the different file counts. Make sure the path on each device’s Web GUI is correct for the folder. Try to access the same path through some file manager and see where you land. Posting screenshots may help us to understand the situation. I don’t think a log file will help you much yet. But while you have the folders still paused, you can look under the respective remote device section what file names it sees as “Out of Sync”.

Hello I don’t find where I can find the 'out of sync list’s the only place where I find some filename is the ‘recent change’ is there another place where I can find some file information?

By the way maybe I have an explanation about the large number of file, on my synology Nas there are a folder @eadir that contains a lot of subfolders used for indexation. I need to exclude it from the synchro. Is it possible to do it in one place or do I have to activate the filter on each folder (android one, Nas one, etc.)

Finally I’m currently synchronizing everything. Both side are identical, non synchronized file is being reduced. I have the feeling it is working without files being transmitted.

How can I check at the end what was really transmitted or not ? Is there a complete log file somewhere ? Because recent change has an history that is unknown. If I understand my files appears in recent change but when scanning discover that file are identical they will disappear from recent changes. Then what is the log that contain the reality of what is done by the synchronization? Transmitted files or not… Modified files or not…

Synchro is over now. I know that nothing was transmitted because synchro was quick. But there are some modified files in the recent change. Whereas I was said that they wouldn’t be. Is there an explanation?

You probably didn’t set the folders to type send-only, as @imsodin recommended?

Files being listed as “recent changes” can even just mean that the timestamps were not identical, maybe caused by time zones or different precision between operating systems. If you are certain that the actual content was already the same, then I trust Syncthing has really brought everything in sync and the “changes” are just cosmetics on the meta-data.

You can get a log of what Syncthing did, but that needs to be enabled in advance of the process itself, and by default does not end up saved to a file. So no, sorry, you will probably not get to review the changes done after the fact. That was the reason for the send-only folder suggestion.

Thanks, so the only way to monitor changes is the ‘recent change’ view.

No history is logged during days or stuff like that to understand in 1 month why this particular photo disappear for instance?

What is the ‘length’ of recent change ? Maximum 50 changes ? Modif during last our ? Last week ? Last month ?

There is an audit log which you can enable using a command line flag when starting Syncthing. But it will collect a huge amount of entries if you just leave it active all the time. Some piece of software could be constructed for listening to the events API and summarizing changes, but I don’t know of any such solution.

Sorry I don’t have an answer about the recent changes list length.

Please check if you want to enable and save logs in your Syncthing home folder, e.g.

syncthing --logfile=default --log-max-size=0 --verbose --audit

but please keep in mind that this will create massive log files that after 1 month can easily become gigabytes in size.

The recent changes are limited to 25 events (see, so the list is very short and honestly not really useful in a large setup.

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