Using the SSH Config File

The ~/.ssh/config file allows us to automate the way we connect to remote servers. Let’s assume you need to access your VPS to deploy an application. The user is deploy and SSH is listening on port 2222 instead of the default port 22. Without the configuration file, you would have to type the following command:

$: ssh -p 2222 -i ~/.ssh/id_ed25519 deploy@[IP]

If you have multiple users or even multiple VPSs, this can start to get complicated, as you will have to enter the command multiple times.

Creating the configuration file

First, let’s start by creating a configuration file. If you already have one, you can skip this part.

$: touch ~/.ssh/config

Basic configuration

Let’s start with the basics. Our first configuration will be for the deploy user we mentioned at the beginning.

Host deploy
  Hostname [IP]
  Port 2222
  User deploy
  IdentityFile ~/.ssh/id_ed25519
  IdentitiesOnly yes

Understanding the options

Now let’s understand what each of these options are.

Host - Here you can add any name you want, but it is recommended to have a good naming convention because this will be the name you will use to connect to the server.

Host deploy

We can also add global settings for the host.

Host *
  AddKeysToAgent yes
  ServerAliveInterval 60

Hostname - In this field, you can enter the server’s IP or DNS.

Hostname [IP]

Port - Here you must enter the port that the server will connect to.

Port 2222

User - In this field, enter the username that will connect.

User deploy

IdentitiesOnly e IdentityFile - Here we are saying that SSH will only use the key we are passing and will not attempt to use any other.

IdentitiesOnly yes
IdentityFile ~/.ssh/id_ed25519

Result

With this configuration, we don’t need to type the command I wrote above. Instead, we can use it this way:

$: ssh deploy