The basic syntax of rsync is very simple, where the content of dir1 is sync to the dir2. Flag -r is for recursively syncing directory. More details can be found at digitalocean.
rsync -r dir1/ dir2
How To Use Rsync to Sync with a Remote System
Syncing to a remote system is easy provided, you have SSH access to the remote machine and rsync installed on both the computers.
rsync -a ~/dir1 username@remote_host:destination_path
List of useful rsync flags
-z for compressing the files to be transferred
-P It combines the flags –progress and –partial. It gives progress bar for the transfers and second allows you to resume interrupted transfers.
More details can be found at rsync help page
rsync --help
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