SSH Config

The SSH config is a file that contains shortcuts for frequently used hosts.

The following stanza:

Host github
  Hostname github.com
  User <username>
  IdentityFile ~/.ssh/id_ed25519

enables you to connect to the github server with this command:

ssh github

instead of the more verbose:

ssh -i ~/.ssh/id_ed25519 <username>@github.com

SSH Config syntax

The SSH config file is a plain text file located at ~/.ssh/config. It can be edited in any text editor.

Each stanza is in the form of:

Host <short name>
  Hostname <remote host name or IP address>
  User <remote user name>
  IdentityFile <path to SSH private key>

Note that indentations are spaces, not tabs.

You can also add a "wildcard" stanza which will apply to all hosts, unless overridden in that host's stanza.

Host *
  AddKeysToAgent yes
  UseKeychain yes
  IdentitiesOnly yes
  IdentityFile ~/.ssh/id_ed25519
  PreferredAuthentications publickey
  User ec2-user

With the above wildcard stanza, the stanza for a host could look like:

Host prod
  Hostname a.b.c.d

If another host uses a different username:

Host prod2
  Hostname w.x.y.z
  User other