Perform commands over ssh with Python

Question:

I’m writing a script to automate some command line commands in Python. At the moment, I’m doing calls like this:

cmd = "some unix command"
retcode = subprocess.call(cmd,shell=True)

However, I need to run some commands on a remote machine. Manually, I would log in using ssh and then run the commands. How would I automate this in Python? I need to log in with a (known) password to the remote machine, so I can’t just use cmd = ssh [email protected], I’m wondering if there’s a module I should be using?

Asked By: fredley

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Answers:

I will refer you to paramiko

see this question

ssh = paramiko.SSHClient()
ssh.connect(server, username=username, password=password)
ssh_stdin, ssh_stdout, ssh_stderr = ssh.exec_command(cmd_to_execute)

If you are using ssh keys, do:

k = paramiko.RSAKey.from_private_key_file(keyfilename)
# OR k = paramiko.DSSKey.from_private_key_file(keyfilename)

ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect(hostname=host, username=user, pkey=k)
Answered By: shahjapan

Or you can just use commands.getstatusoutput:

   commands.getstatusoutput("ssh machine 1 'your script'")

I used it extensively and it works great.

In Python 2.6+, use subprocess.check_output.

Answered By: powerrox

I have used paramiko a bunch (nice) and pxssh (also nice). I would recommend either. They work a little differently but have a relatively large overlap in usage.

Answered By: Eric Snow

I found paramiko to be a bit too low-level, and Fabric not especially well-suited to being used as a library, so I put together my own library called spur that uses paramiko to implement a slightly nicer interface:

import spur

shell = spur.SshShell(hostname="localhost", username="bob", password="password1")
result = shell.run(["echo", "-n", "hello"])
print result.output # prints hello

If you need to run inside a shell:

shell.run(["sh", "-c", "echo -n hello"])
Answered By: Michael Williamson

All have already stated (recommended) using paramiko and I am just sharing a python code (API one may say) that will allow you to execute multiple commands in one go.

to execute commands on different node use : Commands().run_cmd(host_ip, list_of_commands)

You will see one TODO, which I have kept to stop the execution if any of the commands fails to execute, I don’t know how to do it. please share your knowledge

#!/usr/bin/python

import os
import sys
import select
import paramiko
import time


class Commands:
    def __init__(self, retry_time=0):
        self.retry_time = retry_time
        pass

    def run_cmd(self, host_ip, cmd_list):
        i = 0
        while True:
        # print("Trying to connect to %s (%i/%i)" % (self.host, i, self.retry_time))
        try:
            ssh = paramiko.SSHClient()
            ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
            ssh.connect(host_ip)
            break
        except paramiko.AuthenticationException:
            print("Authentication failed when connecting to %s" % host_ip)
            sys.exit(1)
        except:
            print("Could not SSH to %s, waiting for it to start" % host_ip)
            i += 1
            time.sleep(2)

        # If we could not connect within time limit
        if i >= self.retry_time:
            print("Could not connect to %s. Giving up" % host_ip)
            sys.exit(1)
        # After connection is successful
        # Send the command
        for command in cmd_list:
            # print command
            print "> " + command
            # execute commands
            stdin, stdout, stderr = ssh.exec_command(command)
            # TODO() : if an error is thrown, stop further rules and revert back changes
            # Wait for the command to terminate
            while not stdout.channel.exit_status_ready():
                # Only print data if there is data to read in the channel
                if stdout.channel.recv_ready():
                    rl, wl, xl = select.select([ stdout.channel ], [ ], [ ], 0.0)
                    if len(rl) > 0:
                        tmp = stdout.channel.recv(1024)
                        output = tmp.decode()
                        print output

        # Close SSH connection
        ssh.close()
        return

def main(args=None):
    if args is None:
        print "arguments expected"
    else:
        # args = {'<ip_address>', <list_of_commands>}
        mytest = Commands()
        mytest.run_cmd(host_ip=args[0], cmd_list=args[1])
    return


if __name__ == "__main__":
    main(sys.argv[1:])
Answered By: IAmSurajBobade

Have a look at spurplus, a wrapper we developed around spur that provides type annotations and some minor gimmicks (reconnecting SFTP, md5 etc.): https://pypi.org/project/spurplus/

Answered By: marko.ristin

paramiko finally worked for me after adding additional line, which is really important one (line 3):

import paramiko

p = paramiko.SSHClient()
p.set_missing_host_key_policy(paramiko.AutoAddPolicy())   # This script doesn't work for me unless this line is added!
p.connect("server", port=22, username="username", password="password")
stdin, stdout, stderr = p.exec_command("your command")
opt = stdout.readlines()
opt = "".join(opt)
print(opt)

Make sure that paramiko package is installed.
Original source of the solution: Source

Answered By: Alexander Tereshkov

Works Perfectly…

import paramiko
import time

ssh = paramiko.SSHClient()
#ssh.load_system_host_keys()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect('10.106.104.24', port=22, username='admin', password='')

time.sleep(5)
print('connected')
stdin, stdout, stderr = ssh.exec_command(" ")

def execute():
       stdin.write('xcommand SystemUnit Boot Action: Restartn')
       print('success')

execute()
Answered By: Harshan Gowda

Below example, incase if you want user inputs for hostname,username,password and port no.

  import paramiko

  ssh = paramiko.SSHClient()

  ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())



  def details():

  Host = input("Enter the Hostname: ")

  Port = input("Enter the Port: ")

  User = input("Enter the Username: ")

  Pass = input("Enter the Password: ")

  ssh.connect(Host, Port, User, Pass, timeout=2)

  print('connected')

  stdin, stdout, stderr = ssh.exec_command("")

  stdin.write('xcommand SystemUnit Boot Action: Restartn')

  print('success')

  details()
Answered By: Harshan Gowda
#Reading the Host,username,password,port from excel file
import paramiko 
import xlrd

ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())

loc = ('/Users/harshgow/Documents/PYTHON_WORK/labcred.xlsx')
wo = xlrd.open_workbook(loc)
sheet = wo.sheet_by_index(0)
Host = sheet.cell_value(0,1)
Port = int(sheet.cell_value(3,1))
User = sheet.cell_value(1,1)
Pass = sheet.cell_value(2,1)

def details(Host,Port,User,Pass):
    ssh.connect(Host, Port, User, Pass)
    print('connected to ip ',Host)
    stdin, stdout, stderr = ssh.exec_command("")
    stdin.write('xcommand SystemUnit Boot Action: Restartn')
    print('success')

details(Host,Port,User,Pass)
Answered By: Harshan Gowda

Asking User to enter the command as per the device they are logging in.
The below code is validated by PEP8online.com.

import paramiko
import xlrd
import time

ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
loc = ('/Users/harshgow/Documents/PYTHON_WORK/labcred.xlsx')
wo = xlrd.open_workbook(loc)
sheet = wo.sheet_by_index(0)
Host = sheet.cell_value(0, 1)
Port = int(sheet.cell_value(3, 1))
User = sheet.cell_value(1, 1)
Pass = sheet.cell_value(2, 1)

def details(Host, Port, User, Pass):
    time.sleep(2)
    ssh.connect(Host, Port, User, Pass)
    print('connected to ip ', Host)
    stdin, stdout, stderr = ssh.exec_command("")
    x = input('Enter the command:')
    stdin.write(x)
    stdin.write('n')
    print('success')

details(Host, Port, User, Pass)
Answered By: Harshan Gowda

Keep it simple. No libraries required.

import subprocess

# Python 2
subprocess.Popen("ssh {user}@{host} {cmd}".format(user=user, host=host, cmd='ls -l'), shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()

# Python 3
subprocess.Popen(f"ssh {user}@{host} {cmd}", shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()
Answered By: Ronn Macc

The accepted answer didn’t work for me, here’s what I used instead:

import paramiko
import os

ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
# ssh.load_system_host_keys()
ssh.load_host_keys(os.path.expanduser('~/.ssh/known_hosts'))
ssh.connect("d.d.d.d", username="user", password="pass", port=22222)

ssh_stdin, ssh_stdout, ssh_stderr = ssh.exec_command("ls -alrt")
exit_code = ssh_stdout.channel.recv_exit_status() # handles async exit error 

for line in ssh_stdout:
    print(line.strip())

total 44
-rw-r--r--.  1 root root  129 Dec 28  2013 .tcshrc
-rw-r--r--.  1 root root  100 Dec 28  2013 .cshrc
-rw-r--r--.  1 root root  176 Dec 28  2013 .bashrc
...

Alternatively, you can use sshpass:

import subprocess
cmd = """ sshpass -p "myPas$" ssh [email protected] -p 22222 'my command; exit' """
print( subprocess.getoutput(cmd) )

References:

  1. https://github.com/onyxfish/relay/issues/11
  2. https://stackoverflow.com/a/61016663/797495

Notes:

  1. Just make sure to connect manually at least one time to the remote system via ssh (ssh [email protected]) and accept the public key, this is many times the reason from not being able connect using paramiko or other automated ssh scripts.
Answered By: Pedro Lobito

You can use any of these commands, this will help you to give a password also.

cmd = subprocess.run(["sshpass -p 'password' ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null [email protected] ps | grep minicom"], shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
print(cmd.stdout)
OR
cmd = subprocess.getoutput("sshpass -p 'password' ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null [email protected] ps | grep minicom")
print(cmd)
Answered By: Sachin Rastogi

First: I’m surprised that no one has mentioned fabric yet.

Second: For exactly those requirements you describe I’ve implemented an own python module named jk_simpleexec. It’s purpose: Making running commands easy.

Let me explain a little bit about it for you.

The ‘executing a command locally’ problem

My python module jk_simpleexec provides a function named runCmd(..) that can execute a shell (!) command locally or remotely. This is very simple. Here is an example for local execution of a command:

import jk_simpleexec

cmdResult = jk_simpleexec.runCmd(None, "cd / ; ls -la")

NOTE: Be aware that the returned data is trimmed automatically by default to remove excessive empty lines from STDOUT and STDERR. (Of course this behavior can be deactivated, but for the purpose you’ve in mind exactly that behavior is what you will want.)

The ‘processing the result’ problem

What you will receive is an object that contains the return code, STDOUT and STDERR. Therefore it’s very easy to process the result.

And this is what you want to do as the command you execute might exist and is launched but might fail in doing what it is intended to do. In the most simple case where you’re not interested in STDOUT and STDERR your code will likely look something like this:

cmdResult.raiseExceptionOnError("Something went wrong!", bDumpStatusOnError=True)

For debugging purposes you want to output the result to STDOUT at some time, so for this you can do just this:

cmdResult.dump()

If you would want to process STDOUT it’s simple as well. Example:

for line in cmdResult.stdOutLines:
    print(line)

The ‘executing a command remotely’ problem

Now of course we might want to execute this command remotely on another system. For this we can use the same function runCmd(..) in exactly the same way but we need to specify a fabric connection object first. This can be done like this:

from fabric import Connection

REMOTE_HOST = "myhost"
REMOTE_PORT = 22
REMOTE_LOGIN = "mylogin"
REMOTE_PASSWORD = "mypwd"
c = Connection(host=REMOTE_HOST, user=REMOTE_LOGIN, port=REMOTE_PORT, connect_kwargs={"password": REMOTE_PASSWORD})

cmdResult = jk_simpleexec.runCmd(c, "cd / ; ls -la")

# ... process the result stored in cmdResult ...

c.close()

Everything remains exactly the same, but this time we run this command on another host. This is intended: I wanted to have a uniform API where there are no modifications required in the software if you at some time decide to move from the local host to another host.

The password input problem

Now of course there is the password problem. This has been mentioned above by some users: We might want to ask the user executing this python code for a password.

For this problem I have created an own module quite some time ago. jk_pwdinput. The difference to regular password input is that jk_pwdinput will output some stars instead of just printing nothing. So for every password character you type you will see a star. This way it’s more easy for you to enter a password.

Here is the code:

import jk_pwdinput

# ... define other 'constants' such as REMOTE_LOGIN, REMOTE_HOST ...

REMOTE_PASSWORD = jk_pwdinput.readpwd("Password for " + REMOTE_LOGIN + "@" + REMOTE_HOST + ": ")

(For completeness: If readpwd(..) returned None the user canceled the password input with Ctrl+C. In a real world scenario you might want to act on this appropriately.)

Full example

Here is a full example:

import jk_simpleexec
import jk_pwdinput
from fabric import Connection

REMOTE_HOST = "myhost"
REMOTE_PORT = 22
REMOTE_LOGIN = "mylogin"
REMOTE_PASSWORD = jk_pwdinput.readpwd("Password for " + REMOTE_LOGIN + "@" + REMOTE_HOST + ": ")
c = Connection(host=REMOTE_HOST, user=REMOTE_LOGIN, port=REMOTE_PORT, connect_kwargs={"password": REMOTE_PASSWORD})

cmdResult = jk_simpleexec.runCmd(
    c = c,
    command = "cd / ; ls -la"
)
cmdResult.raiseExceptionOnError("Something went wrong!", bDumpStatusOnError=True)

c.close()

Final notes

So we have the full set:

  • Executing a command,
  • executing that command remotely via the same API,
  • creating the connection in an easy and secure way with password input.

The code above solves the problem quite well for me (and hopefully for you as well). And everything is open source: Fabric is BSD-2-Clause, and my own modules are provided under Apache-2.

Modules used:

Happy coding! 😉

Answered By: Regis May

The most modern approach is probably to use fabric. This module allows you to set up an SSH connection and then run commands and get their results over the connection object.

Here’s a simple example:

from fabric import Connection
with Connection("your_hostname") as connection:
    result = connection.run("uname -s", hide=True)
    msg = "Ran {0.command!r} on {0.connection.host}, got stdout:n{0.stdout}"
    print(msg.format(result))
Answered By: leosh

I wrote a simple class to run commands on remote over native ssh, using the subprocess module:

Usage

from ssh_utils import SshClient
client = SshClient(user='username', remote='remote_host', key='path/to/key.pem')

# run a list of commands
client.cmd(['mkdir ~/testdir', 'ls -la', 'echo done!'])

# copy files/dirs
client.scp('my_file.txt', '~/testdir')

Class source code

https://gist.github.com/mamaj/a7b378a5c969e3e32a9e4f9bceb0c5eb

import subprocess
from pathlib import Path
from typing import Union

class SshClient():
    """ Perform commands and copy files on ssh using subprocess 
        and native ssh client (OpenSSH).
    """
    
    def __init__(self,
                 user: str,
                 remote: str,
                 key_path: Union[str, Path]) -> None:
        """

        Args:
            user (str): username for the remote
            remote (str): remote host IP/DNS
            key_path (str or pathlib.Path): path to .pem file
        """
        self.user = user
        self.remote = remote
        self.key_path = str(key_path)
        
        
    def cmd(self, 
            cmds: list[str],
            strict_host_key_checking=False) -> None:
        
        """runs commands consecutively, ensuring success of each
            after calling the next command.

        Args:
            cmds (list[str]): list of commands to run.
            strict_host_key_checking (bool, optional): Defaults to True.
        """
        
        strict_host_key_checking = 'yes' if strict_host_key_checking 
                                    else 'no'
        cmd = ' && '.join(cmds)
        subprocess.run(
            [
                'ssh',
                '-i', self.key_path,
                '-o', f'StrictHostKeyChecking={strict_host_key_checking}', 
                '-o', 'UserKnownHostsFile=/dev/null',
                f'{self.user}@{self.remote}', 
                cmd
            ]
        )
        
        
    def scp(self, source: Union[str, Path], destination: Union[str, Path]):
        """Copies `srouce` file to remote `destination` using the 
            native `scp` command.
            
        Args:
            source (Union[str, Path]): Source file path.
            destination (Union[str, Path]): Destination path on remote.
        """
        subprocess.run(
            [
                'scp',
                '-i', self.key_path,
                str(source), 
                f'{self.user}@{self.remote}:{str(destination)}',
            ]
        )


Answered By: mamaj
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