SSH-protocol

The SSH protocol (also referred to as Secure Shell) is a method for secure remote login from one server to another. SSH-keys are used for user authentication. 

SSH-server

An SSH-server is a set of tools for remote server management and file transfer through the SSH-protocol. 

VMmanager uses the server OpenSSH.

The openssh-client package must be installed on the OpenSSH client and the openssh-server package must be installed on the server. The server component of OpenSSH is waiting for a client connected from any client application. 

Connecting via SSH using a login and password

Execute the command below to connect the  OpenSSH client to the server:  

ssh user@host

You will need to enter the login and password of the remote server. 

Connecting via SSH using SSH-keys

SSH-keys

SSH-keys is a public/private key pair. A private key contains the secret information that remains on the user side. An open key is kept on the remote server.

Generating SSH-keys

On Linux-systems the keys are generated as follows: 

ssh-keygen [options]

The main parameters: -t specifies an encryption algorithm and -b specifies a key length:

ssh-keygen -t rsa -b 4096
ssh-keygen -t dsa
ssh-keygen -t ecdsa -b 521
ssh-keygen -t ed25519

When the keys are generated, the system asks the directory and names for the files that will contain the keys. ".pub" will be added to the public key. 

Coping the public key

You need to copy the user public key to the file  ~/.ssh/authorized_keys on the remote server that will be accessed via SSH :

ssh-copy-id -i ~/.ssh/id_rsa.pub user@host

You will need to enter the login and password of the remote server. 

SSH in VMmanager

VMmanager uses SSH to access virtual machines via SSH-keys.

The control panel keeps user keys and automatically adds them into the file /root/.ssh/authorized_keys on the newly created virtual machines. This authentication method is supported only on Linux-systems provided that an OS template supports this function.