Help for this page
from="the.one.backup.server",command="${HOME}/.ssh/ssh_validate.sh",no +-port-forwarding,no-X11-forwarding,no-agent-forwarding,no-pty ssh-rsa + AA...Rw== some-note-about-this-key
#!/bin/sh case "$SSH_ORIGINAL_COMMAND" in ... rsync*) $SSH_ORIGINAL_COMMAND ;; *) echo "Rejected" ;; esac