How can rsync connect to other nodes without user and password.

I am new to the MariaDB Galera cluster. Questions:
1) How can SST “rsync” method sync files from the donor to the joiner without using a username and password?
2) How can SST “mariabackup” method stream the file from the donor to the joiner? Is it also using rsync  

Hi,These days, you shouldn’t use the rsync SST method, it locks the database (and the then whole cluster) for the duration of the SST.  The MariaBackup and Xtrabackup, those 2 are very similar, are non locking and streams the backup to the joiner node using netcat (nc) or socat on port 4444/TCP by default.