That old laptop could help keep your family files in sync

That old laptop in a cupboard may still have a job. You can use it to keep one family folder in sync with another computer at home. Start with a few test files, not your whole photo collection.

This guide uses Syncthing. Each computer keeps its own copy of the folder. When both are on, changes move between them. The browser page controls the sync; it is not a website where you browse files like Google Drive. This example stays on your home network.

Before you start

You need a spare laptop with a supported 64-bit version of Ubuntu and a second computer. Both need free space and must be on your home Wi-Fi or cable network. The second computer can run Windows, macOS or Linux. This guide will not reinstall or erase the laptop. Keep it awake during the test.

Install Docker Engine and Compose by following Docker's Ubuntu guide. Run sudo docker run hello-world and sudo docker compose version to check the installation. Install Syncthing on the second computer from its official download page.

1. Find the laptop's address

In Ubuntu Settings, find the IPv4 address for the Wi-Fi or cable connection you use. The example below uses 192.168.1.50. Replace it with your laptop's real address every time it appears. If your router can reserve that address for the laptop, do so. Put both computers on the same home network; a guest network may keep them apart.

2. Start one Syncthing container

Open Terminal on the laptop and create a new project folder:

mkdir -p ~/family-sync/data/FamilyDocuments
cd ~/family-sync
id -u
id -g
nano compose.yaml

The two id commands show your user and group numbers. Paste the following into the editor. Replace both 1000 values with your numbers and replace the example IP address with the laptop's address:

services:
  syncthing:
    image: syncthing/syncthing:latest
    environment:
      PUID: "1000"
      PGID: "1000"
    volumes:
      - "./data:/var/syncthing"
    ports:
      - "127.0.0.1:8384:8384"
      - "192.168.1.50:22000:22000/tcp"
    restart: unless-stopped

Save with Ctrl+O and Enter, then leave the editor with Ctrl+X. Run sudo docker compose up -d. On the laptop, open http://127.0.0.1:8384. That address keeps the settings page on the laptop. The other address lets the two computers sync over your home network. Syncthing saves its files and settings in ~/family-sync/data.

3. Keep this example on the home network

On both computers, open Actions → Settings → Connections. Turn off Global Discovery, Local Discovery, Enable Relaying and Enable NAT traversal. Set Sync Protocol Listen Addresses to tcp://0.0.0.0:22000, save and restart if asked. You will enter the laptop's address yourself, so the computers do not need those discovery services.

Give each Syncthing settings page a username and password. Keep the laptop's page at 127.0.0.1:8384. Do not open ports 8384 or 22000 on your router. Docker has its own network rules, so a firewall setting in Ubuntu alone is not enough to keep this setup private.

4. Pair the devices and share one folder

1. On each computer, select Actions → Show ID. Copy the other computer's device ID into Add Remote Device; both sides must approve each other.
2. On the second computer, edit the entry for the laptop. Under Advanced → Addresses, replace dynamic with tcp://192.168.1.50:22000, using your actual laptop address. Save. This computer can now initiate the direct connection.
3. On the laptop, select Add Folder. Use label Family Documents, folder ID family-documents, and path /var/syncthing/FamilyDocuments. Keep the folder type Send & Receive and select the second computer on the Sharing tab.
4. On the second computer, accept the folder invitation. Choose a new empty local folder, such as a folder named FamilyDocuments inside Documents. Keep its folder type Send & Receive.

Create hello.txt in the new folder on the second computer. Write Our family folder works. in it. When both screens say Up to Date, open ~/family-sync/data/FamilyDocuments/hello.txt on the laptop. Add a line there and check that it appears on the second computer. Now you know files can travel both ways.

If the devices do not connect

Check the laptop's IP address, the address entered on the other computer, the device IDs and whether both machines are awake. If a firewall asks about Syncthing, allow it only on your trusted home network. For startup errors, run sudo docker compose logs --tail=50 in ~/family-sync. An address error often means the example IP was not replaced.

Sync needs a separate backup

If you delete a file in a synced folder, that deletion can reach both computers. Syncthing says it is not a backup tool. Before adding precious photos, copy them to a separate drive, disconnect it and test that you can restore a file. Keep older dated copies too.

Once this small test works, add more folders one at a time. Keep Ubuntu updated. Review Syncthing changes before running sudo docker compose pull and sudo docker compose up -d. This setup works at home; access while away is a separate project.