Is another Syncthing instance already running?

Support
1

Hello, everyone!

“WARNING: Failed to acquire lock: is another Syncthing instance already running?”

I am trying to start the Syncthing service, but I get this warning and I don’t see any other instances running or any hints in the logs. Got any idea as to what the issue might be? Thanks in advnace :folded_hands:

systemctl status --user syncthing

syncthing.service - Syncthing - Open Source Continuous File Synchronization
Loaded: loaded (/usr/lib/systemd/user/syncthing.service; enabled; preset: enabled)
Active: failed (Result: exit-code) since Fri 2025-05-23 18:21:42 CEST; 2s ago
Duration: 83ms
Invocation: 260334943c254eac84a7ebb937ef2be9
Docs: man:syncthing(1)
Process: 470126 ExecStart=/usr/bin/syncthing serve --no-browser --no-restart --logflags=0 (code=exited, status=1/FAILURE)
Main PID: 470126 (code=exited, status=1/FAILURE)

maj 23 18:21:42 lapi systemd[1082]: syncthing.service: Scheduled restart job, restart counter is at 4.
maj 23 18:21:42 lapi systemd[1082]: syncthing.service: Start request repeated too quickly.
maj 23 18:21:42 lapi systemd[1082]: syncthing.service: Failed with result ‘exit-code’.
maj 23 18:21:42 lapi systemd[1082]: Failed to start Syncthing - Open Source Continuous File Synchronization.

systemctl status syncthing

Unit syncthing.service could not be found.

journalctl --since “2025-05-23 18:20:00”

maj 23 18:21:37 lapi systemd[1082]: Started Syncthing - Open Source Continuous File Synchronization.
maj 23 18:21:37 lapi syncthing[470060]: [start] INFO: syncthing v1.29.6 “Gold Grasshopper” (go1.24.3 linux-amd64) syncthing@archlinux 2025-05-15 09:30:00 UTC [noupgrade]
maj 23 18:21:37 lapi syncthing[470060]: [start] WARNING: Failed to acquire lock: is another Syncthing instance already running?
maj 23 18:21:37 lapi systemd[1082]: syncthing.service: Main process exited, code=exited, status=1/FAILURE
maj 23 18:21:37 lapi systemd[1082]: syncthing.service: Failed with result ‘exit-code’.
maj 23 18:21:38 lapi systemd[1082]: syncthing.service: Scheduled restart job, restart counter is at 1.
maj 23 18:21:38 lapi systemd[1082]: Started Syncthing - Open Source Continuous File Synchronization.
maj 23 18:21:38 lapi syncthing[470083]: [start] INFO: syncthing v1.29.6 “Gold Grasshopper” (go1.24.3 linux-amd64) syncthing@archlinux 2025-05-15 09:30:00 UTC [noupgrade]
maj 23 18:21:38 lapi syncthing[470083]: [start] WARNING: Failed to acquire lock: is another Syncthing instance already running?
maj 23 18:21:38 lapi systemd[1082]: syncthing.service: Main process exited, code=exited, status=1/FAILURE
maj 23 18:21:38 lapi systemd[1082]: syncthing.service: Failed with result ‘exit-code’.
maj 23 18:21:39 lapi systemd[1082]: syncthing.service: Scheduled restart job, restart counter is at 2.
maj 23 18:21:39 lapi systemd[1082]: Started Syncthing - Open Source Continuous File Synchronization.
maj 23 18:21:39 lapi syncthing[470102]: [start] INFO: syncthing v1.29.6 “Gold Grasshopper” (go1.24.3 linux-amd64) syncthing@archlinux 2025-05-15 09:30:00 UTC [noupgrade]
maj 23 18:21:39 lapi syncthing[470102]: [start] WARNING: Failed to acquire lock: is another Syncthing instance already running?
maj 23 18:21:39 lapi systemd[1082]: syncthing.service: Main process exited, code=exited, status=1/FAILURE
maj 23 18:21:39 lapi systemd[1082]: syncthing.service: Failed with result ‘exit-code’.
maj 23 18:21:40 lapi systemd[1082]: syncthing.service: Scheduled restart job, restart counter is at 3.
maj 23 18:21:40 lapi systemd[1082]: Started Syncthing - Open Source Continuous File Synchronization.
maj 23 18:21:40 lapi syncthing[470126]: [start] INFO: syncthing v1.29.6 “Gold Grasshopper” (go1.24.3 linux-amd64) syncthing@archlinux 2025-05-15 09:30:00 UTC [noupgrade]
maj 23 18:21:40 lapi syncthing[470126]: [start] WARNING: Failed to acquire lock: is another Syncthing instance already running?
maj 23 18:21:40 lapi systemd[1082]: syncthing.service: Main process exited, code=exited, status=1/FAILURE
maj 23 18:21:40 lapi systemd[1082]: syncthing.service: Failed with result ‘exit-code’.
maj 23 18:21:42 lapi systemd[1082]: syncthing.service: Scheduled restart job, restart counter is at 4.
maj 23 18:21:42 lapi systemd[1082]: syncthing.service: Start request repeated too quickly.
maj 23 18:21:42 lapi systemd[1082]: syncthing.service: Failed with result ‘exit-code’.
maj 23 18:21:42 lapi systemd[1082]: Failed to start Syncthing - Open Source Continuous File Synchronization.

2

If Syncthing won’t start because it failed to acquire lock, I’m nearly 100% sure that it’s complaining that it can’t get an exclusive lock on the database. Perhaps you could use lsof or fuser on the database? By default it should be in $HOME/.local/state/syncthing.

3

Try something along those lines:

systemctl status syncthing@$(whoami)

(or if you know the user you care about, systemctl status syncthing@<myuser>

1 Like
4

Jackpot, I keep forgetting that Syncthing requires the instance name matching a user name. I think what threw me off the most this time around was not finding anything under journalctl. It only finds the right logs by entering “journalctl @syncthing” and then the process is simply listed as “syncthing” in the logs.

Lesson learnt? I hope so.

2 Likes
5

I have the same problem so ran this and got

systemctl status syncthing@$(whoami) ○ syncthing@claire.service - Syncthing - Open Source Continuous File Synchroniz> Loaded: loaded (/lib/systemd/system/syncthing@.service; disabled; vendor p> Active: inactive (dead) Docs: man:syncthing(1) lines 1-4/4 (END)

Could you please explain what to do then? Novice here…

6

This would make a nice (CLI) built-in feature, because it works differently on different computers:

$ syncthing status

some sort of report for which users its currently running, or none.