This tutorial will show you how to install Syncthing on Debian. Syncthing is a free, peer-to-peer continuous file synchronization program that allows you to synchronize your files across multiple devices, available for Linux, BSD, macOS, Windows, Android and Solaris.
It’s an open-source alternative to the popular Resilio Sync (formerly known as BitTorrent Sync) application. The creation, modification or deletion of files on one machine will automatically be replicated to your other devices. Syncthing does not upload your files to a central server like Nextcloud, but exchange your data directly between your devices. All your data is encrypted with TLS when transmitting between your devices.
Install Syncthing on Debian via Official Deb Repository
Use curl
to download the GPG key then import the key with apt-key
.
sudo apt-get install curl curl -s https://syncthing.net/release-key.txt | sudo apt-key add -
If you see OK
in the terminal, that means the GPG key is successfully imported. Then add the official deb repository with the following command.
echo "deb https://apt.syncthing.net/ syncthing stable" | sudo tee /etc/apt/sources.list.d/syncthing.list
Becaue this repository uses https, we need to install the apt-transport-https
package, so the APT package manager can establish https connection with this repository.
sudo apt-get install apt-transport-https
Update local package index and install syncthing on Debian.
sudo apt-get update sudo apt-get install syncthing
Using Systemd to Set Up Syncthing as a System Service
The official Syncthing deb package ships with the needed systemd service file. Under /lib/systemd/system/
directory, you will find a [email protected]
file. Enable syncthing to auto start at boot time by running the below command. Replace username with your actual username.
sudo systemctl enable [email protected]username.service
The above command will create a symbolic link that points to the [email protected]
file.
Created symlink from /etc/systemd/system/multi-user.target.wants/[email protected] to /lib/systemd/system/[email protected]
Now we can start the Syncthing service with the following command.
sudo systemctl start [email protected]username.service
Check status
systemctl status [email protected]username.service
Output:
Hint: If the above command doesn’t quit immediately, press Q to gain back control of the terminal.
We can see that Syncthing autostart is enabled and it’s running.
The syncthing systemd service creates configuration files under /home/username/.config/syncthing/
and a folder /home/username/Sync
as the default sync folder. The main config file is /home/username/.config/syncthing/config.xml
.
Install Syncthing on other OS
Go to Syncthing download page and install Syncthing on other operating systems like Windows, macOS, BSD, Android.
Accessing the Debian Syncthing Web Interface
By default, Syncthing service listens on 127.0.0.1:8384. Now in your Web browser’s address bar, type 127.0.0.1:8384
to access the Syncthing Web interface. You can add other Syncthing devices and share folders with them.
If you install Resilio Sync on a remote Debian server, you need to set up a reverse proxy with Nginx or Apache in order to access the web UI, which is explained later in this tutorial.
Start Syncing Files between Your Devices
Once we have two devices running Syncthing, we can start syncing files between them.
In the Syncthing web interfce, click on Actions > Show ID on the upper-right corner. You will see the device ID, which is a long string of letters and numbers. The QR code, which is also the device ID, is used for configuring Syncthing on smartphones.
Copy the device ID, then open the Syncthing Web interface of the second device, click Add Remote Device on the bottom-right corner. Then paste the Device ID and give the device it a name. Click the Save button.
Now the second device will try to connect to the first device. Refresh the Web interface on the first device, you will see the following message. Click Add Device to add the second device to the device list of the first device.
Now the two devices are connected.
One the left pane of Web interface is the default sync folder (/home/username/Sync
). Click the Add Folder
button to add a new folder. Give a descriptive label for this folder and set the folder path.
Syncthing runs as your own user account, so you need to have write permission on the shared folder. If you see the following error message while sharing a folder, it means you don’t have write permission on that folder.
2020-06-21 20:05:49: Failed to create folder marker: mkdir .stfolder: read-only file system
You can grant write permission with setfacl
.
sudo apt install acl
sudo setfacl -R -m u:username:rx /folder/path/
In the Sharing
tab, select your other Syncthing device.
In the Advanced
tab, you can choose the folder type, rescan interval, etc.
Click Save button to begin syncing. A message will appear in the Web interface of the other device. Click Add to receive files.
Now the two devices are syncing files. On the right side, you can see the download rate, upload rate, local folder size, etc.
Set Up Reverse Proxy
Since it listens on 127.0.0.1:8384, Syncthing Web interface is only available to connections from the same computer. To be able to access the Syncthing Web interface from a remote computer, we can set up a reverse proxy for Syncthing with Nginx or Apache.
Nginx
Nginx is a very populuar web server and reverse proxy. If you prefer to use Nginx, run the following command to install it.
sudo apt install nginx
Then create a server config file.
sudo nano /etc/nginx/conf.d/syncthing.conf
Add the following content to this file. Replace syncthing.example.com
with your preferred domain name. You should also add a DNS A record for this sub-domain. If you don’t have a real domain name, I recommend going to NameCheap to buy one. The price is low and they give whois privacy protection free for life.
server {
listen 80;
server_name syncthing.example.com;
access_log /var/log/nginx/syncthing.access.log;
error_log /var/log/nginx/syncthing.error.log;
location / {
proxy_pass http://127.0.0.1:8384;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Proto $scheme;
}
}
Save and close the file. Test Nginx configuration and reload Nginx.
sudo nginx -t sudo systemctl reload nginx
After you point your domain name to the IP address of Debian, type your domain name in the browser address bar and you should see the Syncthing Web interface.
If your browser can’t connect to the Syncthing web interface, perhaps you need to open port 80 in firewall. For example, if you use UFW, then run the following command.
sudo ufw allow 80/tcp
Apache
Apache is well-known web server that can also be used as a reverse proxy. If you prefer Apache to Nginx, install it with:
sudo apt install apache2
Start Apache and enable auto start.
sudo systemctl start apache2 sudo systemctl enable apache2
To use Apache as a reverse proxy, we need to enable the proxy
modules and the header module.
sudo a2enmod proxy proxy_http headers proxy_wstunnel
Now create a virtual host file for Syncthing.
sudo nano /etc/apache2/sites-available/syncthing.conf
Copy and paste the following lines in to the file. Replace syncthing.example.com
with your real domain name. You should also add a DNS A record for this sub-domain. If you don’t have a real domain name, I recommend going to NameCheap to buy one. The price is low and they give whois privacy protection free for life.
ServerName syncthing.example.com
ErrorDocument 404 /404.html
ProxyPass / http://127.0.0.1:8384/
ProxyPassReverse / http://127.0.0.1:8384/
ErrorLog ${APACHE_LOG_DIR}/syncthing_error.log
CustomLog ${APACHE_LOG_DIR}/syncthing_access.log combined
Save and close the file. Then enable this virtual host.
sudo a2ensite syncthing.conf
Restart Apache
sudo systemctl restart apache2
Now you can access the Web UI via syncthing.example.com
.
If your browser can’t connect to the Syncthing web interface, perhaps you need to open port 80 in firewall. For example, if you use UFW, then run the following command.
sudo ufw allow 80/tcp
Secure the Syncthing Web UI with HTTPS
To encrypt the HTTP traffic when you visit Syncthing web UI via a domain name, we can enable HTTPS by installing a free TLS certificate issued from Let’s Encrypt. First, open port 443 in the firewall.
sudo ufw allow 443/tcp
Then run the following command to install Let’s Encrypt client (certbot).
sudo apt install certbot
If you use Nginx, then you also need to install the Certbot Nginx plugin.
sudo apt install python3-certbot-nginx
Next, run the following command to obtain and install TLS certificate.
sudo certbot --nginx --agree-tos --redirect --hsts --staple-ocsp --email [email protected] -d syncthing.example.com
If you use Apache, install the Certbot Apache plugin.
sudo apt install python3-certbot-apache
And run this command to obtain and install TLS certificate.
sudo certbot --apache --agree-tos --redirect --hsts --staple-ocsp --email [email protected] -d syncthing.example.com
Where
--nginx
: Use the nginx plugin.--apache
: Use the Apache plugin.--agree-tos
: Agree to terms of service.--redirect
: Force HTTPS by 301 redirect.--hsts
: Add the Strict-Transport-Security header to every HTTP response. Forcing browser to always use TLS for the domain. Defends against SSL/TLS Stripping.--staple-ocsp
: Enables OCSP Stapling. A valid OCSP response is stapled to the certificate that the server offers during TLS.
The certificate should now be obtained and automatically installed.
Refresh your Syncthing Web GUI, you will find HTTP connection is automatically redirected to HTTPS secure connection.
Enable User Authentication
By default, anyone can access your Syncthing web interface after reverse proxy is setup. We can enable user authentication to restrict access. Click the Actions button on the upper-right corner, then select Settings -> GUI.
Enter a username in GUI Authentication User field, enter a password in GUI Authentication Password field. Then save your settings.
Please note that you don’t need to tick on the Use HTTPS for GUI box, which enables Syncthing to use a self-signed certificate. We have already installed a valid certificate in Apache/Nginx which is trusted by mainstream Web browsers.
Once you save the changes, restart Syncthing systemd service, or you might see a 502 bad gateway error when reloading the page.
sudo systemctl restart [email protected]
Now log into the Syncthing Web interface with your new username and password.
Wrapping Up
I hope this tutorial helped you install and use Syncthing on Debian. As always, if you found this post useful, then subscribe to our free newsletter to get more tips and tricks. Take care 🙂
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