How to backup old files before override them in rsync?

How to back up the old files on the target server before rsync replaces them with new ones?

Use --backup option in rsync. For instance,

# rsync -a --backup --backup-dir="/version2" /var/log/ root@192.168.122.246:/var-log-bk/

This command will copy files from local /var/log to root@192.168.1.100:/var-log-bk/ if rsync overrides some files in 192.168.1.100:/var-log-bk/. It will back up those files to 192.168.1.100:/version2/ first.