> For the complete documentation index, see [llms.txt](https://refdocs.buymeasoda.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://refdocs.buymeasoda.com/unix/secure-shell-ssh.md).

# Secure Shell SSH

## Secure Shell SSH

Connect as `<user>` to remote `<host>` on specified `<port>` If you do not specify a username it uses your current username

```
ssh -p <port> <user>@<host>
```

### SSH Config

Location of SSH settings and host configuration

```
~/.ssh
```

If the SSH directory does not exist create it at `~/.ssh`

```
mkdir ~/.ssh
chmod 700 ~/.ssh
```

If an SSH config file doesn't exist create it at `~/.ssh/config`

```
cd ~/.ssh
touch config
chmod 600 config
```

Add details for a host entry

```
Host <nickname>
  HostName <server>
  User <username>
  Port <port>
```

Use SSH configuration

```
ssh <nickname>
```

Add SSH key passphrase to MacOS Keychain

```
ssh-add -K ~/.ssh/<key-file>
```

If `config` file cannot be edited using `sudo` check the file is not locked in macOS Finder

* File -> Get Info -> General: Locked (Uncheck)

Check the file for the macOS user immutable flag `uchg` (which disallows editing even by the file owner)

```
ls -lO ~/.ssh/config
```

To remove the `uchg` (user immutable) flag and allow the file to be `sudo` edited by the owner

```
chflags nouchg ~/.ssh/config
```

## SSH Access

Connect to remote machine using SSH public / private key instead of username and password.

On the remote machine, if there is no existing `~/.ssh` directory or `~/.ssh/authorized_keys` file, create one:

```
mkdir ~/.ssh && cd ~/.ssh
nano authorized_keys
```

Then past your public key into the file and save.

If an `authorized_keys` file exists, append your key to that file on a new line.