# Configuring SSH

## Setting a Default Username

If your username is different on your tilde than on your personal computer,
you may want to specify a default username in `~/.ssh/config`.
That can be done by adding the following entries:

    Host tilde.black
        User user

## Using a Tilde-Specific key

### Step 1: Generate Your Key

[Generate a key](ed25519.md), except outputting to a Tilde-specific location.

    mkdir -p ~/.ssh/tilde.black
    ssh-keygen -a100 -ted25519 -f ~/.ssh/tilde.black/id_ed25519 -C ''

### Step 2: Authorize Your Key

If you have yet to [sign up](sign-up.md) to your desired Tilde,
send the *public* key (`~/.ssh/tilde.black/id_ed25519.pub`) to the admin.

If you already have an account, you can authorize your new key by adding it to,
or replacing your old key in, `~/.ssh/authorized_keys`.

    $ scp ~/.ssh/tilde.black/id_ed25519.pub user@tilde.black:key.pub
    $ ssh user@tilde.black
    tilde$ cat key.pub >> .ssh/authorized_keys
    tilde$ rm key.pub

### Step 3: Configure SSH

To make `ssh(1)` *only* use that key for that tilde, you can add the following
lines to `~/.ssh/config`:

    Host tilde.black
        IdentitiesOnly yes
        IdentityFile ~/.ssh/tilde.black/id_ed25519

## See Also

[SSH over Tor](ssh-over-tor.md)