I always seem to forget how to do this when I need to. When setting up an automated backup you obviously don't want the script to ask for a password so you set up a key pair.
Machine sending the backups (must be logged in as the user that will be doing the backups):
- ssh-keygen -t dsa -b 2048 -f /any/directory/filename
Then you copy the resulting filename.pub file (NOT the file with no extension) to the authorized_keys file on the receiving machine in the .ssh directory under the user that will receive the backups. If the authorized_keys file doesnt exist, just rename the file you copied... if it does exist, append it to that file.
If your using rsync, use this command:
rsync -e 'ssh -i /any/directory/filename' source/ user@host:/destination/