Install Unison client on Windows

Unison is the best program I found to synchronize files between a Windows PC and a Windows Server over the internet. The only disadvantages are, that Unison doesn’t run in background and that the installation procedure is a little time consuming, as Unison needs ssh, which is not available for Windows as a standalone program.

This how to only covers the installation of the client, as I wrote it when I had to set Unison up again after reinstalling my computer. Maybe at some point I will expand this guide.


  • Download Cygwin from
  • Install Cygwin. During the setup select the package openssh.
  • Start Cygwin and create a key pair by running the command “ssh-keygen”.
  • Assuming you installed Cygwin to C:\cygwin on the server and foo is the user you want to login as, copy the public key ( to C:\cygwin\home\foo\.ssh on the server.
  • Rename the file to authorized_keys.
  • Assuming the username on the client computer is also foo, copy the private key (id_rsa) to C:\cygwin\home\foo\.ssh on the client computer.
  • Copy the file C:\cygwin\etc\defaults\etc\ssh_config to C:\cygwin\etc and edit the ssh settings according to your needs.
  • Test the connection by running “ssh foo@server” in cygwin. No command line options are allowed. Everything has to be setup in ssh_config.
  • Add “C:\cygwin\bin” to the PATH variable in the system settings.


  • Download unison from and extract it to a location of your choice.
  • Download GTK+ for Windows from
  • Extract the GTK+ archive and add the location to the PATH variable in the system settings. You have to restart your computer for the PATH variable to work.
  • Run unison and add a new profile.
  • Select “Using SSH” as synchronization kind and enter host and user name.
  • Select the local directory and type in the remote directory (i. e. “C:\Remote data\foo”).
  • Edit the profile, click on “Add”, select “ignore” and again click on “Add”.
  • Add the entries “Name *.tmp”, “Name thumbs.db”, “Name desktop.ini”, to not synchronize these files.
  • Now click on open in the profile selection. Everything should work.


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