SFTP in Python: Paramiko
28 May 2008
In your scripts or applications, you might need to copy a file from one server to another. One way to do this is to use SFTP, the secure file transfer program, which uses an encrypted SSH (Secure Shell) transport which in turns runs over TCP/IP.
One of the Python implementations of SSH is called Paramiko (available in package managers as paramiko or python-paramiko).
Paramiko is extremely comprehensive so you can get as complicated as you like, but for me, I just want to be able to copy files from a known remotepath to a known localpath and back again.
In this post I explain how to do this using Paramiko directly, in the next-post, I look at another approach.
So we start by importing the module, and specifying the log file:
import paramiko
paramiko.util.log_to_file('/tmp/paramiko.log')
We open an SSH transport:
host = "example.com"
port = 22
transport = paramiko.Transport((host, port))
Next we want to authenticate. We can do this with a password:
password = "example101"
username = "warrior"
transport.connect(username = username, password = password)
Another way is to use an SSH key:
import os
privatekeyfile = os.path.expanduser('~/.ssh/id_rsa')
mykey = paramiko.RSAKey.from_private_key_file(privatekeyfile)
username = 'warrior'
transport.connect(username = username, pkey = mykey)
Now we can start the SFTP client:
sftp = paramiko.SFTPClient.from_transport(transport)
Now lets pull a file across from the remote to the local system:
filepath = '/home/zeth/lenna.jpg'
localpath = '/home/zeth/lenna.jpg'
sftp.get(filepath, localpath)
Now lets go the other way:
filepath = '/home/zeth/lenna.jpg'
localpath = '/home/zeth/lenna.jpg'
sftp.put(filepath, localpath)
Lastly, we need to close the SFTP connection and the transport:
sftp.close()
transport.close()
In my humble opinion, one should not have to write so many lines or care about the SSH protocol just to send a file from a to b. In the next-post, I will share my own higher level API that runs on top of Paramiko.
1 Phill says...
I use Paramiko in the script I have to upload sermons to the Fordham website. It's pretty basic - just creating directories and uploading an MP3. I'm sure I got it to use a key though!
Posted at 4:06 p.m. on May 28, 2008
2 numerodix says...
Is there some reason you can't just use scp?
Posted at 5:09 p.m. on May 28, 2008
3 zeth says...
Phill - I figured it out in the end, see update above.
Numerodix, well that is a valid approach for a small script. However, for an application, spawning a subprocess and running the command-line application scp would be relatively slow and RAM intensive. Paramiko allows us to keep the SSH connection open and perform as many SFTP operations as we like.
Posted at 9:09 p.m. on May 28, 2008
4 Todd Partridge aka Dirk says...
Nice job on the site design. Very viewable! TEXT it's always about text. :)
Posted at 3:54 p.m. on May 29, 2008
5 Harshad Modi says...
Thanks helping me!!! but I have problem on banner.... I try to make my own sftp server using paramiko inherit paramiko.ServerInterface class. but I got this error:
ERROR:paramiko.transport:SSHException: Error reading SSH protocol banner
so can you help me ? how to resloved ?
Posted at 2:58 p.m. on August 18, 2008