SSH

UNIX machines (Mac/Linux) will look for SSH an configuration file at:

$ cat ~/.ssh/config

If the file doesn’t yet exist, create one like so:

$ mkdir -p ~/.ssh
$ touch ~/.ssh/config

If you normally connect to ssh like so:

$ ssh username@remote_machine

Then adding the following to the config, choose a name that makes sense to you…

host my_custom_name
    HostName remote_machine
    User username

…will let you do this:

$ ssh my_custom_name

For passswords, we can create a pair of ssh keys. Follow the prompts, do not set a password for the file, and name it something related to the machine. I’ve named mine “my_key”, but you should pick a better name.

$ ssh-keygen -a 128 -t ed25519

One of the files will end in .pub.

$ cat my_key.pub

This is your public key. The other is your private key, guard it with your life. Sometimes, it is necessary to change the permissions of the private key.

$ chmod 600 my_key

Connect to the remote machine and add the the public key (it should only be one line) to the authorized_keys file.

# on the remote machine
$ echo "the key" >> ~/.ssh/authorized_keys

Adding the following config will use the ssh key instead of the password.

host my_custom_name
    ...
    PreferredAuthentications publickey
    IdentityFile ~/.ssh/my_key

Now you should be able to connect without typing the password as well.

$ ssh my_custom_name

Finally, the following lines tell new connections to use existing connections if possible. This makes it so you only have to do 2FA once.

host my_custom_name
    ...
    ControlMaster auto
    ControlPath ~/.ssh/live_connections/%h_%p_%r

Additional remote machines can be added and settings can be applied to multiple hosts. The following sets both “my_custom_1” and “my_custom_2” to use control master.

host my_custom*
    ControlMaster auto
    ControlPath ~/.ssh/live_connections/%h_%p_%r

host my_custom_1
    ...

host my_custom_2
    ...

Your final config file should look something like this

host my_custom*
    ControlMaster auto
    ControlPath ~/.ssh/live_connections/%h_%p_%r

host my_custom_name
    HostName remote_machine
    User username
    PreferredAuthentications publickey
    IdentityFile ~/.ssh/my_key