Local Sync with Syncthing (LAN) DRAFT

Keep several Linux computers on the same home network in sync using Syncthing. This guide sets up a Syncthing service on Linux Mint Debian Edition (LMDE) that runs automatically at boot and syncs /home/public/PUBLIC-SYNC and /home/jro/JRO-SYNC across all machines.

What this does: any file you add, change, or delete in a shared folder on one computer appears on all the others, over the local network (no cloud, no monthly fee).

Before you start

  • All computers on the same local network (or router).
  • All running Linux Mint Debian Edition (or similar Debian-based system).
  • You have sudo access on each machine.
  • Suggested: three Dell computers — two desktops and one laptop.

Step 1 — Install Syncthing

Run these commands on each computer:

sudo apt update
sudo apt install -y syncthing

Check it installed:

syncthing --version

Step 2 — Create the shared folders

Create the folders you want to sync, on each computer. Use the exact same paths everywhere.

sudo mkdir -p /home/public/PUBLIC-SYNC
sudo mkdir -p /home/jro/JRO-SYNC

Set reasonable ownership so your normal user can use them:

sudo chown -R jro:jro /home/public/PUBLIC-SYNC
sudo chown -R jro:jro /home/jro/JRO-SYNC

(Adjust the username if yours is different from jro.)

Step 3 — Create a systemd service to run as root

Syncthing normally runs as the logged-in user. To run it as a background service that starts at boot (even before you log in), create a systemd service file on each computer.

Create the service definition:

sudo nano /etc/systemd/system/syncthing-root.service

Paste the following:

[Unit]
Description = Syncthing (root service for LAN sync)
After = network-online.target
Wants = network-online.target

[Service]
Type = simple
ExecStart = /usr/bin/syncthing serve --home=/etc/syncthing
Restart = on-failure
User = root
Group = root

[Install]
WantedBy = multi-user.target

Save and close (in nano: Ctrl+O, Enter, then Ctrl+X).

Why run as root? The folders live under /home/public and /home/jro, and this keeps one simple configuration shared across the machines. If you prefer, you can skip this and run Syncthing as your normal user instead — the steps are the same, just omit User=root.

Step 4 — Enable and start the service

sudo systemctl daemon-reload
sudo systemctl enable syncthing-root.service
sudo systemctl start syncthing-root.service

Verify it is running:

sudo systemctl status syncthing-root.service

You should see Active: active (running).

The service will also start automatically on every boot from now on.

Step 5 — Pair the computers together

Syncthing uses the web interface to set up syncing. Open it on each computer:

Open your browser and go to http://127.0.0.1:8384.

Then, on the first computer:

  1. Click Actions → Show ID and copy the device ID (a long fingerprint string).
  2. On the second computer, click Add Remote Device and paste the first computer's ID.
  3. Repeat so each computer knows the others.

For three computers (A, B, C), add: - A → B and A → C - B → A and B → C - C → A and C → B

Step 6 — Add the folders

Now connect each folder to the devices:

  1. On each computer, click Add Folder.
  2. Folder ID: public-sync, Folder Path: /home/public/PUBLIC-SYNC. Under Sharing, tick every other computer.
  3. Create a second folder: Folder ID: jro-sync, Folder Path: /home/jro/JRO-SYNC. Tick every other computer.
  4. Click Save.

Use the same Folder ID on all computers so Syncthing knows they are the same folder.

Step 7 — Test it

  1. On computer A, create a test file: bash echo "hello" > /home/public/PUBLIC-SYNC/test.txt
  2. Wait a few seconds, then check computer B: bash cat /home/public/PUBLIC-SYNC/test.txt
  3. If you see hello, syncing works. Delete the test file when done.

Step 8 — Keep it running

Everything is automatic from here:

  • Syncthing starts on boot and runs in the background.
  • New, changed, and deleted files propagate to all connected computers.
  • You can monitor status anytime at http://127.0.0.1:8384 on any machine.

Managing the service

sudo systemctl status syncthing-root.service   # check status
sudo systemctl restart syncthing-root.service  # restart
sudo systemctl stop syncthing-root.service     # stop

Troubleshooting

  • Folders not appearing: make sure the Folder ID matches on every computer and the folder is shared with the correct devices.
  • Can't reach the web UI: confirm the service is running with sudo systemctl status syncthing-root.service, then reload the page at http://127.0.0.1:8384.
  • Sync is slow: Syncthing syncs over the local network; make sure all machines are on the same router/subnet.
  • Permission errors: confirm ownership is set (Step 2) with ls -la /home/public.

Summary

You now have a self-hosted, always-on sync system across your Dell computers using Syncthing as a root systemd service. Add a file on one machine and it shows up on all the others — no cloud service required.