Syncthing Device ID keeps switching

Chris073 · April 11, 2025, 4:42am

A desktop I have paired with my laptop has switched device ID’s twice now. I open the syncthing UI on my laptop and the desktop won’t connect and I get a message up top saying the desktop is requesting to connect. I check the ID on the desktop and sure enough it has switched to something new. This is the second time this has happened in the last week or two. I’m running Syncthing 1.29.4 on both devices with auto updates to the stable branch enabled. Any reason this may happen? Syncthing has been running fine on both devices with no issues for a few years now until the past 2 weeks.

marbens · April 11, 2025, 4:46am

Crosspost of Syncthing Device ID keeps switching?

calmh · April 11, 2025, 5:58am

The only way this happens is if something else has deleted the certificate files on disk, or changed the directory Syncthing uses to store them.

Chris073 · April 11, 2025, 6:08am

Yep

Chris073 · April 11, 2025, 6:10am

Any idea what could have done that? It’s a mostly standard Windows 10 machine. Could it be anti-virus?

marbens · April 11, 2025, 6:20am

Also could happen if some program was modifying the files themselves directly, but this is less likely.

tomasz86 · April 11, 2025, 8:04am

Maybe something caused by chore(syncthing): use file lock on certificate to prevent multiple in… · syncthing/syncthing@7762e39 · GitHub? The change came in v1.29.4, so the time frame would match.

I think a log file would be helpful here.

terry · April 11, 2025, 10:20pm

I’ve noticed that if I close St and reopen before St has fully shutdown, it will generate a new ID. Not sure if it’s related to Syncthing Tray as I have only just started using it and has happened only in the same time frame.

I have had to restore backups to get the ID back, but remote devices saw the new IDs and wanted me to reconnect to them…

Chris073 · April 11, 2025, 10:32pm

That could definitely be it. I have a scheduled task set to restart syncyhing every hour to make sure it’s running properly. I had issues where syncthing would be running and the ui was accessible, but it never connected to other devices. A restart fixed it and the scheduled task automated that.

tomasz86 · April 12, 2025, 12:04am

github.com/syncthing/syncthing

Trying to launch Syncthing when already running resets cert.pem to 0 bytes

opened 12:04AM - 12 Apr 25 UTC

tomasz1986

bug needs-triage

### What happened? 1. Start Syncthing. 2. Try to start Syncthing again using th…e same `--config` (or `--home`) directory. 3. The new instance fails to start with the following error: ``` [start] 2025/04/12 01:58:55.751711 main.go:432: INFO: syncthing v2.0.0-beta.6 "Hafnium Hornet" (go1.24.2 windows-amd64) builder@github.syncthing.net 2025-04-07 09:43:08 UTC [stnoupgrade] [start] 2025/04/12 01:58:55.751711 utils.go:64: INFO: Generating ECDSA key and certificate for syncthing... [start] 2025/04/12 01:58:55.753718 main.go:440: WARNING: Failed to load/generate certificate: save cert: write R:\test\syncthing\syncthing1\cert.pem: The process cannot access the file because another process has locked a portion of the file. [monitor] 2025/04/12 01:58:55.755224 monitor.go:199: INFO: Syncthing exited: exit status 1 ``` 4. Despite that, the `cert.pem` file has been wiped out and has a size of 0 bytes. Tested under Windows 10 x64. Ref 1: https://github.com/syncthing/syncthing/commit/7762e39fb3ad90a13034d43039112583cd0f514b Ref 2: https://forum.syncthing.net/t/syncthing-device-id-keeps-switching/24147 ### Syncthing version v1.27.4 and beta v2 ### Platform & operating system Windows ### Browser version _No response_ ### Relevant log output ```shell ```

calmh · April 12, 2025, 1:18pm

A fix for this is out in 1.29.5 now.

Chris073 · April 12, 2025, 5:09pm

Excellent! Wow that was fast. You guys rock!

system · May 12, 2025, 5:09pm

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