SSH linux Putty .ppk OpenSSH
How to convert a putty private key file (.ppk) to openssh format on Mac operating system.
SSH linux utilities
Information and quick-use guide for the linux utility 'ssh_copy_id'
Ubuntu Ubuntu 16.04 SSH SFTP system administration config files
How to grant users SFTP access via the /etc/ssh/sshd_config file in Ubuntu 16.04