Secure Copy File from remote server via scp and os module in Python

Question

I'm pretty new to Python and programming. I'm trying to copy a file between two computers via a python script. However the code

os.system("ssh " + hostname + " scp " + filepath + " " + user + "@" + localhost + ":" cwd)

won't work. I think it needs a password, as descriped in How to copy a file to a remote server in Python using SCP or SSH?. I didn't get any error logs, the file just won't show in my current working directory.

However every other command with os.system("ssh " + hostname + "command") or os.popen("ssh " + hostname + "command") does work. -> command = e.g. ls

When I try ssh hostname scp file user@local:directory in the commandline it works without entering a password.

I tried to combine os.popen commands with getpass and pxssh module to establish a ssh connection to the remote server and use it to send commands directly (I only tested it for an easy command):

import pxssh
import getpass

ssh = pxssh.pxssh()
ssh.force_password = True
hostname = raw_input("Hostname: ")
user = raw_input("Username: ")
password = getpass.getpass("Password: ")
ssh.login(hostname, user, password)
test = os.popen("hostname")
print test

But I'm not able to put commands through to the remote server (print test shows, that hostname = local and not the remote server), however I'm sure, the conection is established. I thought it would be easier to establish a connection than always use "ssh " + hostname in the bash commands. I also tried some of the workarounds in How to copy a file to a remote server in Python using SCP or SSH?, but I must admit due to lack of expirience I didn't get them to work.

Thanks a lot for helping me.

Why do you think you need to do ssh hostname scp? Why not just scp user@hostname:file localdirectory? — Daniel Roseman
– Daniel Roseman, Commented Nov 24, 2011 at 9:54
Prefer the subprocess module over os.system() for security reasons. — glglgl
– glglgl, Commented Nov 24, 2011 at 10:09
I haven't thought about the posibility to copy via scp user@hostname:file localdirectory. It does work, but only when I cancel the user@ part. — user1063572
– user1063572, Commented Nov 24, 2011 at 10:39
I didn't know the subprocess module until now, but I will take it into consideration (as I said I'm new to python and learning, I need some time to adopt) — user1063572
– user1063572, Commented Nov 24, 2011 at 10:42

englebip · Accepted Answer · 2011-11-24 16:06:25Z

4

I think the easiest (to avoid having to enter a password) and most secure way to go about this is to first set public/private key authentication. Once that is done, and you can log in to the remote system by doing ssh user@hostname, the following bash command would do the trick:

scp some/complete/path/to/file user@remote_system:some/remote/path

The corresponding Python code would be:

import subprocess

filepath = "some/complete/path/to/file"
hostname = "user@remote_system"
remote_path = "some/remote/path"

subprocess.call(['scp', filepath, ':'.join([hostname,remote_path])])

answered Nov 24, 2011 at 16:06

englebip

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