Rsync is a powerful utility for efficiently transferring and synchronizing files across computer systems, using a delta transfer algorithm to minimize network usage. It supports various options for copying files securely and efficiently, making it widely used for backups and mirroring. Rsync operates both in client-server mode and in a standalone mode for local file copying.

┌ Open a terminal and switch to root

su -

┌ Install rsync on both client and server machines:
(you'll probably have to choose between 2 repos for the package, take the distribution repo first)

pkg install rsync

┌ Generate and share an SSH key
(without passphrase) for secure connections.

┌ Basic Rsync commands

• To send a file to the server :

rsync -avzP -e "ssh -p 47689" /local/path file remoteuser@remoteserver:/destination/path

• To fetch a file from the server:

rsync -avzP -e "ssh -p 47689" remoteuser@remoteserver:/source/path /local/dest/path/

┌ More Options :

• Compression: Use --compress-level=9 for maximum compression.

• Exclusion/Inclusion: Use --exclude='*.tmp' to exclude, --include='*.txt' to include.

• Bandwidth Limit: Use --bwlimit=1000 to limit network usage to 1000KB/s.

• Logging: Use --log-file=rsync.log for detailed tracking.

• Dry Run: Add --dry-run to simulate transfers.
  

┌ Security and Performance Tips:

• Use --checksum for content-based verification rather than relying on timestamps and file sizes.

• Integrate specific SSH options for enhanced security, like -oCiphers=....

• For efficient backups, consider leveraging ZFS snapshots.

Here's an example command that incorporates several of the above elements, designed for quick use in most scenarios :

rsync -avzP --compress-level=9 --exclude='*.tmp' --bwlimit=1000 --log-file=rsync.log -e "ssh -p 47689 -oCiphers=aes256-gcm@openssh.com" /local/path/ remoteuser@remoteserver:/destination/path/

Explanations :

• -avzP : Enables archive mode to preserve permissions, compresses during transfer, and shows progress.
  Be carefull with archive mode as it uses A LOT OF RAM !

• --compress-level=9 : Uses the highest level of compression to save bandwidth.

• --exclude='*.tmp' : Excludes all temporary files from the transfer to avoid sending unnecessary data.

• --bwlimit=1000 : Limits bandwidth usage to 1000 KB/s to avoid saturating your connection.

• --log-file=rsync.log : Creates a log file to track transfer details.

• -e "ssh -p 52333 -oCiphers=aes256-gcm@openssh.com" : Specifies using SSH for connection, on a custom port (52333) and with a specific cipher for improved security.