rsync to remote machine

rsync.sh

rsync -avz --delete --progress \
      -e "ssh -i ~/.ssh/my_private_key" \ # or just `-e ssh` (see below)
      /SOURCE_PATH username@1.2.3.4:/DESTINATION_PATH
      
# Breaking down:

# -a, --archive               archive mode; equals -rlptgoD (no -H,-A,-X)
#
#     -r, --recursive             recurse into directories
#     -l, --links                 copy symlinks as symlinks
#     -p, --perms                 preserve permissions
#     -t, --times                 preserve modification times
#     -g, --group                 preserve group
#     -o, --owner                 preserve owner (super-user only)
#     -D                          same as --devices --specials
#         --devices                   preserve device files (super-user only)
#         --specials                  preserve special files

# --delete                    delete extraneous files from dest dirs

# --progress                  show progress during transfer

# -e, --rsh=COMMAND           specify the remote shell to use
#
#     If you are using public-key authentication and your
#     private key's name differs from the default then you
#     can provide it with `-i`.
#
#     From `man ssh`:

#     -i identity_file
#             Selects a file from which the identity (private key) for public
#             key authentication is read.  The default is ~/.ssh/identity for
#             protocol version 1, and ~/.ssh/id_dsa, ~/.ssh/id_ecdsa,
#             ~/.ssh/id_ed25519 and ~/.ssh/id_rsa for protocol version 2.
#             Identity files may also be specified on a per-host basis in the
#             configuration file.  It is possible to have multiple -i options
#             (and multiple identities specified in configuration files).  If
#             no certificates have been explicitly specified by the
#             CertificateFile directive, ssh will also try to load certificate
#             information from the filename obtained by appending -cert.pub to
#             identity filenames.