Syncthing is a modern file synchronization tool. It synchronizes files between various devices and operating systems. It is a great tool for automatic backup of personal files and smartphones. It has several usefull features:
- Easy and simple configuration
- File versioning
- File ignore patterns
For this setup we will use GlusterFS as the file store backend.
Start by installing syncthing
apt-get install syncthing
Configure your system as a GlusterFS client, so you have the following in your fstab.
/etc/glusterfs/home.vol /srv/home glusterfs defaults,_netdev,rw 0 0
For each user that is going to synchronize against this system, create a directory for them in /srv/home and give it the correct ownership.
mkdir /srv/home/kale chown -R kale:kale /srv/home/kale
For each user add the syncthing service to default runlevel and start it.
systemctl enable email@example.com systemctl start firstname.lastname@example.org
When the syncthing service starts, it creates a set of config files in the users home directory. Edit /home/kale/.config/syncthing/config.xml and look for the section below. Change the address, so the service listens on all interfaces <address>0.0.0.0:8384</address>, instead of just localhost. Notice that when you make this change, your syncthing service is public. Everyone can change it.
Restart the service for the specific user.
systemctl restart email@example.com
It should now be possible to connect to the syncthing GUI on https://syncthing:8384 and configure it.
Start by setting up a username, a password and force https. This is done in the settings dialog in the GUI tab. Your installation should now be secure.
When transferring files, the default behavior of syncthing is to flush for every file transferred. This makes transfer of many small files very slow. The version of syncthing provided in Debian Buster does not have an option to disable syncthings use of the fsync call. In newer versions of syncthing, this can be found in ~/.config/syncthing/config.xml as <disableFsync>false</disableFsync>. Changing that option to true will make syncthing transfer files much faster, on the expense of risking data loss. Currently the version of syncthing in Debian Bullseye does have this functionality implemented.
Using syncthing from bullseye
On a side note, it looks like the modern version (1.18.1) of the syncthing application for android, does not work with the version (1.0.0) of syncthing in Buster. It was not possible to get the two to sync properly. Using the version (1.12.1) from Bullseye made the sync possible.
Set your default release in /etc/apt/apt.conf.d/99defaultrelease by adding.
Add the bullseye repository to /etc/apt/sources.list.d/bullseye.list
deb http://deb.debian.org/debian/ bullseye main contrib non-free
Then setup pinning in /etc/apt/preferences.d/buster.pref
Package: * Pin: release a=buster Pin-Priority: 1000
And in /etc/apt/preferences.d/bullseye.pref
Package: syncthing Pin: release a=bullseye Pin-Priority: 500
Install syncthing from bullseye
apt-get update apt-get -u install syncthing/bullseye
Using eat my data
A library called libeatmydata has been created to stop applications like syncthing from using fsync, by replacing the fsync library call.
apt-get install eatmydata
Link syncthing to eatmydata
ln -s /usr/bin/eatmydata /usr/local/bin/syncthing
Now change the init script for the syncthing service in /lib/systemd/system/syncthing@.service to use the version of syncthing in /usr/local/bin, and eatmydata will take care of the fsync call.
1 [Unit] 2 Description=Syncthing - Open Source Continuous File Synchronization for %I 3 Documentation=man:syncthing(1) 4 After=network.target 5 6 [Service] 7 User=%i 8 ExecStart=/usr/local/bin/syncthing -no-browser -no-restart -logflags=0 9 Restart=on-failure 10 SuccessExitStatus=3 4 11 RestartForceExitStatus=3 4 12 13 # Hardening 14 ProtectSystem=full 15 PrivateTmp=true 16 SystemCallArchitectures=native 17 MemoryDenyWriteExecute=true 18 NoNewPrivileges=true 19 20 [Install] 21 WantedBy=multi-user.target
Let systemd know that you changed a service
Finally restart the syncthing service
systemctl restart firstname.lastname@example.org