To compress a rar archive in multiple parts, just do a command below:
$ rar a -vSIZE ARCHIVE.rar FILES/FOLDER
– SIZE in K is kilobyte, M in megabyte, etc
– ARCHIVE.rar is the archive name, it will be ARCHIVE.part1.rar ARCHIVE.part2.rar etc as the results.
– FILES/FOLDER is the file or folder that we want to add to archive