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Custom SSH Connections

SSH (SSH client) is a program for remotely accessing a machine, and can be easily installed from repositories. By default, users are authenticated in ssh using passwords, however, we can setup SSH Passwordless Login for easy access.

SSH config files

There is a default system-wide configuration file. It contains settings that apply to all users of ssh client machine. Here we will the user-specific/custom configuration file. located at ~/.ssh/config or $HOME/.ssh/config. It has configurations that apply to a specific user. It therefore overrides default settings in the system-wide config file. This is the file we will create and use.

Usually ~/.ssh directory already exists, but In case it does not exist on your desktop system, create it with the following permissions. 

mkdir -p ~/.ssh
chmod 0700 ~/.ssh

Now, we Create user specific SSH configuration file which is not created by defaut. We can use following command to create this file with proper permissions. 

touch ~/.ssh/config
chmod 0700 ~/.ssh/config

The conventional format of ~/.ssh/config is as follows, 

Host    host1
    ssh_option1=value1
    ssh_option2=value1 value2
    ssh_option3=value1 

Host    host2
    ssh_option1=value1
    ssh_option2=value1 value2

Host  *
    ssh_option1=value1
    ssh_option2=value1 value2

and, the syntax to login is then, 

ssh host1
Note

For more detailed and explanation visit here

Working Example

Open the config file using any editor of choice. Here we are using Vim to do that. 

vim ~/.ssh/config

and define the necessary sections as shown below in the config file. 

Host myfedora37
        HostName 192.168.56.15
        Port 22
        ForwardX11 no

Host myraspi
        HostName 192.168.56.10
        Port 22
        ForwardX11 no

Host myubuntu22
        HostName 192.168.56.5
        Port 2222
        ForwardX11 yes

Host *
        User raviroy
        IdentityFile ~/.ssh/id_rsa
        Protocol 2
        Compression yes
        ServerAliveInterval 60
        ServerAliveCountMax 20
        LogLevel INFO

  • HostName – defines the real host name to log into, alternatively, you can use a numeric IP addresses, it is also permitted (both on the command line and in HostName specifications).

  • User – specifies the user to log in as.

The above values and the Host host1 should be changed accordingly. We can add as many hosts as we want.

Once that is done, we can login simply by typing in Terminal 

ssh myfedora37 # to login into myfedora37


ssh myraspi # to login into myraspi

Source : Configure Custom SSH Connections to Simplify Remote Access Tecmint