Fabric SSH Automation

3.2.3 · active · verified Thu Apr 09

Fabric is a high-level Python library for streamlining SSH command execution and application deployment. It is currently at version 3.2.3 and releases updates on an as-needed basis, typically for bug fixes or minor enhancements, building on Invoke and Paramiko.

Warnings

breaking Fabric 2.x and 3.x are NOT backward compatible with Fabric 1.x. The API was completely rewritten, moving from global state ('env') to an object-oriented design centered around the 'Connection' object.
Fix: Rewrite Fabric 1.x scripts to use the new `Connection` object-based API. Consult the Fabric 2.x migration guide for details.
gotcha Global state ('env') from Fabric 1.x is gone. Tasks now receive a `Connection` object (`c`) as their first argument, which holds all connection-specific information and methods.
Fix: Access connection properties via `c.host`, `c.user`, `c.config`, etc., and call methods like `c.run()`, `c.sudo()`.
gotcha The global functions `run()`, `sudo()`, `local()`, `put()`, `get()` from Fabric 1.x are now methods of the `Connection` object (e.g., `c.run()`, `c.sudo()`).
Fix: Replace calls like `run('command')` with `c.run('command')`. Similarly for `sudo`, `local`, `put`, `get`.
gotcha Context managers like `cd()`, `warn_only()`, `settings()` from Fabric 1.x are also now methods of the `Connection` object (e.g., `with c.cd('/path'):`).
Fix: Ensure all context manager usage is prefixed with the `Connection` object, e.g., `with c.cd('/tmp'): c.run('ls')`.
gotcha Configuration is handled via the `Config` object or directly on `Connection` instances, not global dictionaries. Passing parameters to tasks requires explicit arguments or configuration.
Fix: Define task parameters explicitly (`@task(arg1='default')`), or configure connection parameters via `Connection` constructor, or `fab` CLI flags (`-H`, `-u`, `-i`, `-p`).

Install

pip install fabric Install Fabric

Imports

Connection
```
from fabric import Connection
```
Fabric 2.x+ removed the global 'env' state from Fabric 1.x. All operations now happen on a 'Connection' object.
task
```
from fabric import task
```
While 'task' might exist in 1.x 'fabric.api', the modern Fabric 2.x+ API directly imports from 'fabric'.

Quickstart

Create a `fabfile.py` with tasks. Each task receives a `Connection` object `c` as its first argument. Run tasks from the command line using `fab -H user@host task_name`.

# fabfile.py
from fabric import Connection, task

@task
def hello(c):
    """
    Runs a simple command on the remote host.
    Example usage: fab -H user@localhost hello
    
    Note: For 'localhost' to work, an SSH server must be running 
    and your user configured for SSH access.
    """
    print(f"Connecting to {c.host} as {c.user or 'default'}...")
    # Run a command, hiding the command itself from stdout, only showing output
    result = c.run("echo Hello from $(hostname)", hide=True)
    print(f"Output: {result.stdout.strip()}")

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