# Hosts

To define a new host use the [host()](api.md#host) function. Deployer keeps a list of
all defined hosts in the `Deployer::get()->hosts` collection.

```php
host('example.org');
```

Each host contains it's own configuration key-value pairs. The [host()](api.md#host)
call defines two important configs: **alias** and **hostname**.

- **hostname** - used when connecting to remote host.
- **alias** - used as a key in `Deployer::get()->hosts` collection.

```php
task('test', function () {
    writeln('The {{alias}} is {{hostname}}');
});
```

```
$ dep test
[example.org] The example.org is example.org
```

We can override hostname via `set()` method:

```php
host('example.org')
    ->set('hostname', 'example.cloud.google.com');
```

The hostname will be used for the ssh connection, but the host will be referred
by its alias when running Deployer.

```
$ dep test
[example.org] The example.org is example.cloud.google.com
```

Another important ssh connection parameter is `remote_user`.

```php
host('example.org')
    ->set('hostname', 'example.cloud.google.com')
    ->set('remote_user', 'deployer');
```

Now Deployer will connect using something like
`ssh deployer@example.cloud.google.com` to establishing connection.

Also, Deployer's `Host` class has special setter methods (for better IDE
autocompletion).

```php
host('example.org')
    ->setHostname('example.cloud.google.com')
    ->setRemoteUser('deployer');
```

## Host config

### `alias`

The identifier used to identify a host. 
You can use actual hostname or something like `prod` or `staging`.

### `hostname` 

Deployer uses this config for actual ssh connection.

### `remote_user` 

Deployer uses this config for actual ssh connection. If not specified, 
Deployer will be using `RemoteUser` from **~/.ssh/config** file, or current
OS username.

### `port` 

Port of remote ssh server to connect to. Default is `22`.

### `config_file` 

Default is `~/.ssh/config`.

:::info Config file
It is a good practice to keep connection parameters out of `deploy.php` file, as
they can change depending on where the deploy is executed from. Only specify
`hostname` and `remote_user` and other keep in `~/.ssh/config`:

```
Host *
  IdentityFile ~/.ssh/id_rsa
```
:::

### `identity_file` 

For example, `~/.ssh/id_rsa`.

### `forward_agent` 

Default is `true`.

### `ssh_multiplexing` 

Default is `true`.

### `shell` 

Default is `bash -ls`.

### `deploy_path` 

For example, `~/myapp`.

### `labels` 

Key-value pairs for host selector.

### `ssh_arguments` 

For example, `['-o UserKnownHostsFile=/dev/null']`

### `ssh_control_path`

Default is `~/.ssh/%C`.

If **CI** env is present, default value is `/dev/shm/%C`. 

## Multiple hosts

You can pass multiple hosts to the host function:

```php
host('example.org', 'deployer.org', ...)
    ->setRemoteUser('anton');
```

## Host ranges

If you have a lot of hosts following similar patterns, you can describe them
like this rather than listing each hostname:

```php
host('www[01:50].example.org');
```

For numeric patterns, leading zeros can be included or removed, as desired.
Ranges are inclusive.

You can also define alphabetic ranges:

```php
host('db[a:f].example.org');
```

## Localhost

The [localhost()](api.md#localhost) function defines a special local host.
Deployer will not connect to this host, but will execute commands locally instead.

```php
localhost(); // Alias and hostname will be "localhost".
localhost('ci'); // Alias is "ci", hostname is "localhost".
```

## YAML Inventory

You can use the [import()](api.md#import) function to keep host definitions in a
separate file. For example, *inventory.yaml*.

```php title="deploy.php"
import('inventory.yaml');
```

```yaml title="inventory.yaml"
hosts:
  example.org:
    remote_user: deployer
  deployer.org:
    remote_user: deployer
```