Use an arbitrary key file with SSH, Scp, Rsync and Ansible

Connections to cloud-hosted servers are typically secured using an RSA Private Key rather than password. If you have the key saved to a file on a local machine, here is how to use it with SSH, Scp, Rsync and Ansible

SSH

To use SSH to perform a remote login, use the -i parameter to specify a path to the local key file, like:

ssh -i /path/to/file-with-private.key remote-user@remote-ip-or-hostname

Scp

To use Scp to securely copy a file to or from a host, use the -i parameter again. For example, to copy file.txt from your remote host to your local current directory:

scp -i /path/to/file-with-private.key remote-user@remote-ip-or-hostname:/remote-path/file.txt ./

Or, to copy file.txt from your local current directory to a remote host:

scp -i /path/to/file-with-private.key ./file.txt remote-user@remote-ip-or-hostname:/remote-path/

Rsync

Rsync, to synchronise with a remote filesystem, requires passing an SSH environment variable, like this:

rsync -avz -e "ssh -p1234 -i /path/to/file-with-private.key" /local/directory remote-user@remote-ip-or-hostname:/remote/directory

Ansible

To enable management of your remote host using Ansible, edit your /etc/ansible/hosts file and append one line per remote host requiring a key file, as per the following format:

remote-host-or-ip ansible_user=remote-user ansible_ssh_private_key_file=/path/to/file-with-private.key