Part 2: Connect from your computer

7. SSH from a Mac#

What you'll do: control the server from your Mac's Terminal, first with a password, then with a key (safer, and no password typing). Time: 20 minutes.

What is SSH? What is a key?#

SSH opens the server's terminal inside a window on your Mac. Everything you type there runs on the server.

A key is a pair of files:

flowchart LR
  subgraph Mac["Your Mac"]
    PK["Private key<br/>id_ed25519_homeserver<br/>NEVER share"]
  end
  subgraph Server["Server"]
    PUB["Public key<br/>(copy in authorized_keys)<br/>safe to share"]
  end
  PK -- "proves it's you" --> PUB

Think of the public key as a lock you install on the server, and the private key as the only key that opens it. The private key never leaves your Mac.

Step 1: First connection (with password)#

ssh alex@homeserver.local

The first time, you see:

The authenticity of host 'homeserver.local' can't be established.
ED25519 key fingerprint is SHA256:Xy3...
Are you sure you want to continue connecting (yes/no/[fingerprint])?

Type yes and press Enter. Then type your server password (nothing shows while you type).

The prompt changes to alex@homeserver:~$, so you're on the server. Type exit to come back to your Mac.

Step 2: Make a key (on your Mac)#

ssh-keygen -t ed25519 -f ~/.ssh/id_ed25519_homeserver -C "mac-homeserver"

It asks for a passphrase. Choose one and save it in your password manager. The passphrase protects the key if your Mac is stolen.

This creates two files: id_ed25519_homeserver (private) and id_ed25519_homeserver.pub (public).

Step 3: Copy the public key to the server#

ssh-copy-id -i ~/.ssh/id_ed25519_homeserver.pub alex@homeserver.local

Type your server password one last time. It should say Number of key(s) added: 1.

Step 4: Create a shortcut#

So you can type ssh homeserver instead of the long command:

nano ~/.ssh/config

Paste this at the end of the file (keep anything already there):

Host homeserver
    HostName homeserver.local
    User alex
    IdentityFile ~/.ssh/id_ed25519_homeserver
    IdentitiesOnly yes
    AddKeysToAgent yes
    UseKeychain yes

Save with Ctrl+O Enter and exit with Ctrl+X.

Step 5: Remember the passphrase in the Mac Keychain#

ssh-add --apple-use-keychain ~/.ssh/id_ed25519_homeserver

Type the key passphrase once.

Step 6: Test#

ssh homeserver

You should be on the server without typing any password.

Next: 8. SSH from Windows (if you have a PC), otherwise 10. Lock SSH