Blog | Fabric as ssh on steroids on Debian Stretch

Fabric is a library and command-line tool that generates a workflow of tasks for automating deployments and administrative tasks remotely.

This article is based on a youtube video with an introduction to Fabric.

https://youtu.be/bY2U4ikgezk

There are 3 machines:

192.168.1.3: Machine with Debian Stretch where fabric is installed.
192.168.1.2: Machine with Debian Stretch.
192.168.1.6: Machine with Debian Jessie.

Only one machine with Fabric is needed. Debian Stretch is used because in this version of Debian Fabric is not so complicated to install; on Debian Jessie it has given me some problems: it installs but gives errors at runtime (from what I have researched, the problem is the paramiko library).

Installing Fabric: With pip:

#pip install fabric

Now create a fabfile.py file with the following content:

#!/usr/bin/env python

#de la api de fabric de importa run, sudo, task, get y put

from fabric.api import run,sudo,task,get, put



#Se define la tareta cmdrun que ejectua el argumento

@task

def cmdrun(arg):

    run(arg)



#Se define la tarea sudorun que ejecuta el argumento vía sudo

@task

def sudorun(arg):

    sudo(arg)



#Se define la tarea download que se le pasa un argumento que se descarga en /tmp/

@task

def download(arg):

    get(remote_path=arg,local_path="/tmp/",use_sudo=True)



#Se define la tarea upload que se le pasa dos argumentos

#local_path y remote_path.

@task

def upload(arg1,arg2):

    put(local_path=arg1,remote_path=arg2,use_sudo=True)



#Se define la tarea host_type que ejecuta uname.

@task

def host_type():

        run('uname -s')

To run the tasks, use the fab command (an environment variable called clave is defined, holding the user's password):

Running ps on two machines in parallel:

fab -H 192.168.1.2,192.168.1.6 -p $clave -P cmdrum:"ps -ef|wc -l"

It returns the output of ps and the number of lines that result on each machine.

The host type of each remote machine is found with host_type:

fab -H 192.168.1.2,192.168.1.6 -p $clave   host_type

Here the commands are run sequentially on the machines; to run them in parallel, use the -P option.

fab -H 192.168.1.2,192.168.1.6 -p $clave  -P host_type

The execution is no longer done sequentially on each machine.

Run fdisk through sudo:

fab -H 192.168.1.2,192.168.1.6 -p $clave -P sudo:"fdisk -l| grep sda"

The command returns the sda partitions that each machine has.

Upload a sources.list file to machine 192.168.1.2 through upload, passing the local file and the remote path as arguments:

fab -h 192.168.1.2 -p $clave upload:"sources.list","/tmp/"

The figure shows that the file upload was done without problems; now check the /tmp/ directory: The figure shows that the sources.list file is in /tmp/

Download the file prueba.txt from machine 192.168.1.2 through download, passing the remote path of the file; this file is downloaded by default to /tmp/:

fab -H 192.168.1.2 -p $clave upload:"sources.list","/tmp/"

In this case the file /home/ernesto/prueba.txt was downloaded to /tmp/, and then the file was listed locally to verify that it is in that directory.

A more complete tutorial on Fabric can be found on its site.

Ernesto Crespo.

Summary

Fabric as ssh on steroids on Debian Stretch