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Use Paramiko and Python to SSH into a Server
Traducciones al EspañolEstamos traduciendo nuestros guías y tutoriales al Español. Es posible que usted esté viendo una traducción generada automáticamente. Estamos trabajando con traductores profesionales para verificar las traducciones de nuestro sitio web. Este proyecto es un trabajo en curso.
When your Python program needs to run an external password-dependent program, or access a remote server, use Paramiko . Paramiko is a Python module that implements the SSHv2 protocol. Paramiko is not part of Python’s standard library, although it’s widely used. This guide shows you how to use Paramiko in your Python scripts to authenticate to a server using a password and SSH keys.
Before You Begin
If you have not already done so, create a Linode account and Compute Instance. See our Getting Started with Linode and Creating a Compute Instance guides.
Follow our Setting Up and Securing a Compute Instance guide to update your system. You may also wish to set the timezone, configure your hostname, create a limited user account, and harden SSH access.
Install Paramiko
You must install Paramiko on your system before being able to use it in your Python programs. Use the command below to install Paramiko with Pip:
pip install paramiko
If your system is configured to use Anaconda , you can use the following command to install Paramiko:
conda install -c anaconda paramiko
A Paramiko SSH Example: Connect to Your Server Using a Password
This section shows you how to authenticate to a remote server with a username and password. To begin, create a new file named first_experiment.py
and add the contents of the example file. Ensure that you update the file with your own Linode’s details. Replace the values for YOUR_IP_ADDRESS
, YOUR_LIMITED_USER_ACCOUNT
, and YOUR_PASSWORD
. Use the Find Your Linode’s IP Address
guide, if needed.
- File: password_login.py
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import paramiko command = "df" # Update the next three lines with your # server's information host = "YOUR_IP_ADDRESS" username = "YOUR_LIMITED_USER_ACCOUNT" password = "YOUR_PASSWORD" client = paramiko.client.SSHClient() client.set_missing_host_key_policy(paramiko.AutoAddPolicy()) client.connect(host, username=username, password=password) _stdin, _stdout,_stderr = client.exec_command("df") print(_stdout.read().decode()) client.close()
This file connects to remote server over SSH using the IP address and credentials that you provide. It then uses the df
command to generate a report of your server’s free disk space.
Execute the file with the following command:
python password_login.py
You see a similar output:
Filesystem 1K-blocks Used Available Use% Mounted on
devtmpfs 1921544 0 1921544 0% /dev
tmpfs 1936296 0 1936296 0% /dev/shm
tmpfs 1936296 211308 1724988 11% /run
tmpfs 1936296 0 1936296 0% /sys/fs/cgroup
/dev/mapper/cl-root 46110724 20501872 25608852 45% /
/dev/sda1 999320 187324 743184 21% /boot
The file above provides a high-level example that you can use to incorporate Paramiko into your Python code. While everything Paramiko does can also be done with shell commands, Paramiko gives you all the power of Python. Python gives you access to structuring data, looping, parsing, and other powerful features that go beyond what is available in shell scripting. For example, if you are writing a program to calculate system usage percentages, Python is better at extracting and calculating values from your system’s output.
Second Paramiko Example: Connect to your Server Using SSH Keys
One of Paramiko’s specific strengths is the correct handling of SSH add keys
. The introductory example above depended on the use of your limited user account’s password. It is more secure, however, to use SSH keys for server authentication. The example file below, provides a report that alerts you of any logins by users that are not included in your list of expected
users. The Python script relies on Paramiko (notice the key_based_connect()
function) to use SSHv2 authentication to connect to any of the servers provided in the code’s server_list
list.
- File: key_based_login.py
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# This is a small tool to report on successful logins # to accounts other than those listed in the variable # expected. Such a report might lead to an investigation # into how and why those other accounts were logging in. import paramiko def examine_last(server, connection): command = "sudo last" expected = ["user1", "reboot", "root", "sys-admin"] _stdin, stdout, _stderr = connection.exec_command("sudo last") lines = stdout.read().decode() connection.close() for line in lines.split("\n"): # Ignore the last line of the last report. if line.startswith("wtmp begins"): break parts = line.split() if parts: account = parts[0] if not account in EXPECTED: print(f"Entry '{line}' is a surprise on {server}.") def key_based_connect(server): host = "192.0.2.0" special_account = "user1" pkey = paramiko.RSAKey.from_private_key_file("./id_rsa") client = paramiko.SSHClient() policy = paramiko.AutoAddPolicy() client.set_missing_host_key_policy(policy) client.connect(host, username=special_account, pkey=pkey) return client def main(): server_list = ["worker1", "worker2", "worker3"] for server in server_list: connection = key_based_connect(server) examine_last(server, connection) main()
Execute the file with the following command:
python key_based_login.py
If a user outside of the Python script’s expected
list accesses one of your servers, the Python script returns the following:
Entry user4 pts/0 192.0.2.0 Wed Sep 23 15:13 - 17:28 (02:14)' is a surprise on 192.0.2.0.
Going Further with Paramiko
Paramiko helps you automate repetitive system administration tasks on remote servers. More advanced Paramiko programs send the lines of a script one at a time. It does this rather than transacting all of a command, such as df
or last
, synchronously to completion. Paramiko is a helpful addition to your system administrator toolchain when working to automate common tasks. You can visit Paramiko’s documentation
to learn about its special-purpose methods and variables that go beyond the examples covered in this guide.
More Information
You may wish to consult the following resources for additional information on this topic. While these are provided in the hope that they will be useful, please note that we cannot vouch for the accuracy or timeliness of externally hosted materials.
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