We have setup an Ubuntu server for the purpose of provide SFTP accounts for a number of users. Each user has an account and can upload files to their respective home directories. We are using vsftpd and key pairs. The users do not have SSH access.
The issue I'm having is that I'd like to prevent users from modifying or deleting the authorized_keys file in their /home/user/.ssh directory.
Ideally, we'd prefer that they not see or modify these files and directories, all under the /home/user directory:
And instead, they would only access the /home/user/files directory.
Any suggestions on how to accomplish this?