Machine A holds important source data that needs to be backed up. Machine B is where the data will be backed up to. They're both Ubuntu. I want to have an automated process that allows machine A to create an encrypted tarball and copy it to machine B, without human intervention, but doesn't allow anything except copying the file over to a target directory.
I thought about using a chroot jailed account, but this seems to be a pain to set up and overly complex. I really just want to be able to have machine A to copy files to machine B, via automatic cron, but I also want to prevent the mechanism that allows the copy from allowing any other actions (copying to any other directory, logging in, executing any other commands noninteractively, etc.). Also, the transfer must be encrypted (e.g. using ssh somehow).