SSH keys and passwordless login

To synchronize to a remote server, RsyncUI requires passwordless SSH key authentication. Password-based authentication is not supported. SSH keys are more secure than passwords and allow RsyncUI to run unattended tasks without prompting.

Default SSH keys

If you use the standard RSA key location (~/.ssh/id_rsa) and the default port 22, no extra configuration is needed in RsyncUI. RsyncUI detects the key automatically and appends -e ssh to the rsync command to tunnel and encrypt the transfer.

Custom SSH keys

If you prefer a non-default key location or a custom port, you must create the key pair manually and tell RsyncUI where to find it.

RsyncUI passes custom key settings to rsync as:

-e "ssh -i ~/.keypath/identityfile -p NN"

where:

• -i ~/.keypath/identityfile is the SSH keypath and identity file
• -p NN is the port number (default 22)

Custom keypaths must start with ~ followed by / and contain at least two forward slashes. RsyncUI validates this before saving.

For example, a custom keypath might look like:

~/.ssh_rsyncosx/rsyncosx

And the resulting rsync command RsyncUI builds would be:

/opt/homebrew/bin/rsync --archive --verbose --compress \
-e "ssh -i ~/.ssh_rsyncosx/rsyncosx -p 22" --stats \
/Users/thomas/Documents/ thomas@raspberrypi:/backups/Documents/

Step-by-step: creating a custom SSH key pair

RsyncUI uses the standard tools ssh-keygen and ssh-copy-id. Run the following steps in Terminal.

Step 1: Create the SSH directory

cd
mkdir .ssh_rsyncosx

Step 2: Generate the key pair

ssh-keygen -t rsa -N "" -f ~/.ssh_rsyncosx/rsyncosx

Parameters explained:

• -t rsa — creates an RSA key pair
• -N "" — sets no passphrase
• -f ~/.ssh_rsyncosx/rsyncosx — specifies where to save the keys

Step 3: Copy the public key to the remote server

ssh-copy-id -i ~/.ssh_rsyncosx/rsyncosx.pub -p NN user@server

Replace NN with your SSH port (default 22), user with your remote username, and server with your server address.

Step 4: Set correct permissions

chmod 700 ~/.ssh_rsyncosx

Step 5: Verify the connection

/usr/bin/ssh -p NN -i ~/.ssh_rsyncosx/rsyncosx user@server

A successful login confirms the key pair is working. If it fails, check that ssh-copy-id completed without errors and that the permissions on ~/.ssh_rsyncosx are correct.

Step 6: Configure RsyncUI

Open Settings → SSH and enter your custom keypath and identity file. RsyncUI will apply these settings to all remote tasks. You can also set per-task SSH parameters in the task’s Parameters tab, which will override the global setting.