Being a Pro with SSH

Contents

  1. Reduce your Typing
    1. Passwordless Login
    2. Aliases
    3. Tunneling

1. Reduce your Typing

Let host=apklinkh@guardian.it.mtu.edu. We will learn how to log in quickly to this server, even if the name is quite long.

1.1. Passwordless Login

We can generate a key pair stored on the current machine at ~/.ssh/id_rsa.pub (public, safe to share) and ~/.ssh/id_rsa (private, never share this one).

ssh-keygen -t rsa -b 4096

Just use the defaults by hitting enter. Then, we append the content of ~/.ssh/id_rsa.pub to ~/.ssh/authorized_keys on the host machine.

ssh-copy-id $host

And that's all! You should be able to ssh $host without a password! For passwordless login to subsequent machines, all you need to do is run the ssh-copy-id command.

1.2. Aliases

If $host is very long to type, or even if it's short, we can make it shorter by adding the following lines to ~/.ssh/config.

## ~/.ssh/config
Host wopr
User apklinkh
Hostname guardian.it.mtu.edu

Now we can type ssh wopr instead of apklinkh@guardian.it.mtu.edu.

1.3. Tunneling

Sometimes you want to ssh to a host that you can only reach from an internal network. If you have access to a machine on the internal network, some additions to ~/.ssh/config make it possible to ssh directly to the desired machine. In this example, superior is the machine that we want to access, but we must tunnel through wopr.

## ~/.ssh/config
Host wopr
User apklinkh
Hostname guardian.it.mtu.edu

Host superior
User apklinkh
Hostname superior-login1.research.mtu.edu
ProxyCommand ssh wopr /usr/bin/nc %h %p 2>/dev/null