================
Salt File Server
================

Salt comes with a simple file server suitable for distributing files to the
Salt minions. The file server is a stateless ZeroMQ server that is built into
the Salt master.

The main intent of the Salt file server is to present files for use in the
Salt state system. With this said, the Salt file server can be used for any
general file transfer from the master to the minions.

The cp Module
-------------

The cp module is the home of minion side file server operations. The cp module
is used by the Salt state system, salt-cp and can be used to distribute files
presented by the Salt file server.

Environments
````````````

Since the file server is made to work with the Salt state system, it supports
environments. The environments are defined in the master config file and
when referencing an environment the file specified will be based on the root
directory of the environment.

get_file
````````

The cp.get_file function can be used on the minion to download a file from
the master, the syntax looks like this:

.. code-block:: bash

    # salt '*' cp.get_file salt://vimrc /etc/vimrc

This will instruct all Salt minions to download the vimrc file and copy it
to /etc/vimrc

Template rendering can be enabled on both the source and destination file names
like so:

.. code-block:: bash

    # salt '*' cp.get_file "salt://{{grains.os}}/vimrc" /etc/vimrc template=jinja

This example would instruct all Salt minions to download the vimrc from a
directory with the same name as their OS grain and copy it to /etc/vimrc

For larger files, the cp.get_file module also supports gzip compression.
Because gzip is CPU-intensive, this should only be used in
scenarios where the compression ratio is very high (e.g. pretty-printed JSON
or YAML files).

Use the *gzip* named argument to enable it.  Valid values are 1..9,
where 1 is the lightest compression and 9 the heaviest.  1 uses the least CPU
on the master (and minion), 9 uses the most.

.. code-block:: bash

    # salt '*' cp.get_file salt://vimrc /etc/vimrc gzip=5

Finally, note that by default cp.get_file does *not* create new destination
directories if they do not exist.  To change this, use the *makedirs* argument:

.. code-block:: bash

    # salt '*' cp.get_file salt://vimrc /etc/vim/vimrc makedirs=True

In this example, /etc/vim/ would be created if it didn't already exist.

get_dir
```````

The cp.get_dir function can be used on the minion to download an entire
directory from the master.  The syntax is very similar to get_file:

.. code-block:: bash

    # salt '*' cp.get_dir salt://etc/apache2 /etc

cp.get_dir supports *template* rendering and *gzip* compression arguments just
like get_file:

.. code-block:: bash

    # salt '*' cp.get_dir salt://etc/{{pillar.webserver}} /etc gzip=5 template=jinja


File Server Client API
----------------------

A client API is available which allows for modules and applications to be
written which make use of the Salt file server.

The file server uses the same authentication and encryption used by the rest
of the Salt system for network communication.

FileClient Class
````````````````

The FileClient class is used to set up the communication from the minion to
the master. When creating a FileClient object the minion configuration needs
to be passed in. When using the FileClient from within a minion module the
built in ``__opts__`` data can be passed:

.. code-block:: python

    import salt.minion

    def get_file(path, dest, env='base'):
        '''
        Used to get a single file from the Salt master

        CLI Example:
        salt '*' cp.get_file salt://vimrc /etc/vimrc
        '''
        # Create the FileClient object
        client = salt.minion.FileClient(__opts__)
        # Call get_file
        return client.get_file(path, dest, False, env)

Using the FileClient class outside of a minion module where the ``__opts__``
data is not available, it needs to be generated:

.. code-block:: python

    import salt.minion
    import salt.config

    def get_file(path, dest, env='base'):
        '''
        Used to get a single file from the Salt master
        '''
        # Get the configuration data
        opts = salt.config.minion_config('/etc/salt/minion')
        # Create the FileClient object
        client = salt.minion.FileClient(opts)
        # Call get_file
        return client.get_file(path, dest, False, env)

