How to setup a proper SFTP user in linux?

It sounds like you want is a chroot for sftp. Here are several questions that ask the same question. Keep in mind that chroot is not really meant to be a solution for security since in some cases the user can escape from a chroot. You should make sure your system is still secure if they manage to escape the chroot. Using a chroot is a fine solution if you are just wanting to make the system easier for your users to use.

  • Securing file system for secure SFTP server
  • How can I chroot ssh connections?
  • It is fair to jail my SFTP users to their home directory?
  • How to secure SFTP wihtout re-compiling OpenSSH?
  • set up a chrooted SFTP login with OpenSSH