fabric2 2.1.3

High level SSH command execution

To find out what’s new in this version of Fabric, please see the changelog.

What is Fabric?

Fabric is a high level Python (2.7, 3.4+) library designed to execute shell commands remotely over SSH, yielding useful Python objects in return:

>>> from fabric import Connection
>>> result = Connection('web1.example.com').run('uname -s')
>>> msg = "Ran {.command!r} on {.host}, got this stdout:\n{.stdout}"
>>> print(msg.format(result))
Ran "uname -s" on web1.example.com, got this stdout:
Linux

It builds on top of Invoke (subprocess command execution and command-line features) and Paramiko (SSH protocol implementation), extending their APIs to complement one another and provide additional functionality.

How is it used?

Core use cases for Fabric include (but are not limited to):

• Single commands on individual hosts:

  >>> result = Connection('web1').run('hostname')
  web1
  >>> result
  <Result cmd='hostname' exited=0>

• Single commands across multiple hosts (via varying methodologies: serial, parallel, etc):

  >>> result = SerialGroup('web1', 'web2').run('hostname')
  web1
  web2
  >>> result
  {<Connection host=web1>: <Result cmd='whoami' exited=0>, ...}

• Python code blocks (functions/methods) targeted at individual connections:

  >>> def disk_free(c):
  >>>     uname = c.run('uname -s', hide=True)
  >>>     if 'Linux' in uname:
  ...         command = "df -h / | tail -n1 | awk '{print $5}'"
  ...         return c.run(command, hide=True).stdout.strip()
  ...     err = "No idea how to get disk space on {}!".format(uname)
  ...     raise Exit(err)
  ...
  >>> disk_free(Connection('web1'))
  '33%'

• Python code blocks on multiple hosts:

  >>> def disk_free(c):
  ...     # same as above!
  ...
  >>> {c: disk_free(c) for c in SerialGroup('web1', 'web2', 'db1')}
  {<Connection host=web1>: '33%', <Connection host=web2>: '17%', ...}

In addition to these library-oriented use cases, Fabric makes it easy to integrate with Invoke’s command-line task functionality, invoking via a fab binary stub:

• Python functions, methods or entire objects can be used as CLI-addressable tasks, e.g. fab deploy;

• Tasks may indicate other tasks to be run before or after they themselves execute (pre- or post-tasks);

• Tasks are parameterized via regular GNU-style arguments, e.g. fab deploy --env=prod -d;

• Multiple tasks may be given in a single CLI session, e.g. fab build deploy;

• Much more - all other Invoke functionality is supported - see its documentation for details.

I’m a user of Fabric 1, how do I upgrade?

We’ve packaged modern Fabric in a manner that allows installation alongside Fabric 1, so you can upgrade at whatever pace your use case requires. There are multiple possible approaches – see our detailed upgrade documentation for details.