To use Rsync with a different key, follow the command structure below.
rsync -e "ssh -i $HOME/.ssh/key" user@hostname:/from/dir/ /to/dir/
Though for syncing my local website to my VPS, I usually like having more options with my rsync command
rsync -Paz --delete -e "ssh -i $HOME/.ssh/key" user@hostname:/from/dir/ /to/dir/
Quick option definitions (from man page)
|-e||Allows you to override the default shell used as the transport for rsync. Command line options are permitted after the command name.|
|-a, –archive||This is equivalent to -rlptgoD. It is a quick way of saying you want recursion and want to preserve almost everything (with -H being a notable omission). The only exception to the above equivalence is when –files-from is specified, in which case -r is not implied.
Note that -a does not preserve hardlinks, because finding multiply-linked files is expensive. You must separately specify -H.
|-P||Equivalent to –partial –progress. Its purpose is to make it much easier to specify these two options for a long transfer that may be interrupted.|
|-z, –compress||Compress file data during the transfer|
|–delete||Delete extraneous files from dest dirs|