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Abdeladim Fadheli · 4 min read · Updated may 2024 ·Ethical Hacking

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Have you ever wanted to quickly execute certain commands remotely on your Linux machine? or do you want to routinely execute some lines of code in your server to automate stuff? In this tutorial, you will learn how to write a simple Python script to remotely execute shell commands on your Linux machine.

We will be using theparamiko library; let's install it:

pip3 install paramiko

Defining some connection credentials:

import paramikohostname = "192.168.1.101"username = "test"password = "abc123"

In the above code, I've defined thehostname,username, andpassword, this is my local Linux box, you need to edit these variables for your case, or you may want to make command-line argument parsing using theargparse module as we usually do in such tasks.

Note that it isn't safe to connect to SSH using credentials like that. You can configure your SSH listener daemon to accept only public authentication keys instead of using a password. However, for demonstration purposes, we will be using a password.

Executing Shell Commands

Now, let's create a list of commands you wish to execute on that remote machine:

commands = [    "pwd",    "id",    "uname -a",    "df -h"]

In this case, simple commands output useful information about the operating system.

The below code is responsible for initiating theSSH client and connecting to the server:

# initialize the SSH clientclient = paramiko.SSHClient()# add to known hostsclient.set_missing_host_key_policy(paramiko.AutoAddPolicy())try:    client.connect(hostname=hostname, username=username, password=password)except:    print("[!] Cannot connect to the SSH Server")    exit()

Now let's iterate over the commands we just defined and execute them one by one:

# execute the commandsfor command in commands:    print("="*50, command, "="*50)    stdin, stdout, stderr = client.exec_command(command)    print(stdout.read().decode())    err = stderr.read().decode()    if err:        print(err)

Here are my results:

================================================== pwd ==================================================/home/test================================================== id ==================================================uid=1000(test) gid=0(root) groups=0(root),27(sudo)================================================== uname -a ==================================================Linux rockikz 4.17.0-kali1-amd64 #1 SMP Debian 4.17.8-1kali1 (2018-07-24) x86_64 GNU/Linux================================================== df -h ==================================================Filesystem      Size  Used Avail Use% Mounted onudev            1.9G     0  1.9G   0% /devtmpfs           392M  6.2M  386M   2% /run/dev/sda1       452G  410G   19G  96% /tmpfs           2.0G     0  2.0G   0% /dev/shmtmpfs           5.0M     0  5.0M   0% /run/locktmpfs           2.0G     0  2.0G   0% /sys/fs/cgrouptmpfs           392M   12K  392M   1% /run/user/131tmpfs           392M     0  392M   0% /run/user/1000

Awesome, these commands were successfullyexecutedon my Linux machine!

Executing Scripts

Now that you know how to execute commands one by one, let's dive a little bit deeper and execute entire shell (.sh) scripts.

Consider this script (named"script.sh"):

cd Desktopmkdir test_foldercd test_folderecho "$PATH" > path.txt

After theSSH connection, instead of iterating for commands, now we read the content of this script and execute it:

# read the BASH script content from the filebash_script = open("script.sh").read()# execute the BASH scriptstdin, stdout, stderr = client.exec_command(bash_script)# read the standard output and print itprint(stdout.read().decode())# print errors if there are anyerr = stderr.read().decode()if err:    print(err)# close the connectionclient.close()

exec_command() method executes the script using the default shell (BASH,SH, or any other) and returns standard input, standard output, and standard error, respectively. We will read fromstdout andstderr if there are any, and then we will close theSSH connection.

After the execution of the above code, a new filetest_folder was created inDesktop and got a text file inside that which contained the global$PATH variable:

Results after executing the Script in Python

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Conclusion

As you can see, this is useful for many scenarios. For example, you may want to manage your servers only by executing Python scripts remotely; you can do anything you want!

And by the way, If you want to run more complex jobs on a remote server, you might want to look intoAnsible instead.

You can also useFabric library, as it is a high-level Python library designed just to execute shell commands remotely over SSH. It builds on top ofInvoke andParamiko.

Feel free to edit the code as you wish; for example, you may want to parse command-line arguments withargparse.

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Happy Coding ♥

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