How can I run multiple commands on SSH in one go with Paramiko in Python?

Question

I've got some code that runs through a list of devices, connects to them via SSH and queries some parameters. The basic code looks like this:

ssh = paramiko.SSHClient()
ssh.connect(ip_address, username='root', password=password)

try:
    ssh_stdin, ssh_stdout, ssh_stderr = ssh.exec_command('uname -r')
    if ssh_stdout.channel.recv_exit_status() == 0:
        temp = ssh_stdout.readlines()
        if temp:
            kernel_version = temp[0].strip('\n').strip('\"')
except BaseException as ex:
    print(f'An exception occurred: {ex}')

try:
    ssh_stdin, ssh_stdout, ssh_stderr = ssh.exec_command('lsb_release -rs')
    if ssh_stdout.channel.recv_exit_status() == 0:
        temp = ssh_stdout.readlines()
        if temp:
            ubuntu_version = temp[0].strip('\n').strip('\"')
except BaseException as ex:
    print(f'An exception occurred: {ex}')

But there are a lot of devices and it takes a long time to run. It's faster to run multiple commands in one go:

try:
    ssh_stdin, ssh_stdout, ssh_stderr = ssh.exec_command('uname -r; lsb_release -rs')
    if ssh_stdout.channel.recv_exit_status() == 0:
        temp = ssh_stdout.readlines()
        if temp[0]:
            kernel_version = temp[0].strip('\n').strip('\"')
        if temp[1]:
            ubuntu_version = temp[1].strip('\n').strip('\"')
except BaseException as ex:
    print(f'An exception occurred: {ex}')

but how can I handle one command passing and one failing? Is there a better way of doing this?

You can improve your second code by printing an exit code of each command and parsing it from the output. Or you can parallelize connections to multiple servers to speed up the overal operation. — Martin Prikryl
– Martin Prikryl, Commented Jun 8 at 18:08

lei zhang · Accepted Answer · 2025-06-27 09:27:56Z

2

You can implement parallelism on top of this by using multithreading to reduce time.

import paramiko


def get_kernel_ubuntu_version_raw(ip_address, password):
    ssh = paramiko.SSHClient()
    ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
    ssh.connect(ip_address, username="root", password=password)

    try:
        ssh_stdin, ssh_stdout, ssh_stderr = ssh.exec_command("uname -r")
        if ssh_stdout.channel.recv_exit_status() == 0:
            temp = ssh_stdout.readlines()
            if temp:
                kernel_version = temp[0].strip("\n").strip('"')
    except BaseException as ex:
        print(f"An exception occurred: {ex}")
    try:
        ssh_stdin, ssh_stdout, ssh_stderr = ssh.exec_command("lsb_release -rs")
        if ssh_stdout.channel.recv_exit_status() == 0:
            temp = ssh_stdout.readlines()
            if temp:
                ubuntu_version = temp[0].strip("\n").strip('"')
    except BaseException as ex:
        print(f"An exception occurred: {ex}")

And I try to use send&recv instead of exec_command.


def get_kernel_ubuntu_version(ip_address, password):
    prompt = r"#\s+$"
    ssh = paramiko.SSHClient()
    ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
    ssh.connect(ip_address, username="root", password=password)
    chan = ssh.get_transport().open_session()
    chan.get_pty()
    chan.invoke_shell()

    try:
        chan.send(b"uname -r\n")
        kernel_version = ""
        while not re.search(prompt, kernel_version):
            kernel_version += chan.recv(1024).decode(errors="ignore")
        print(f"{ip_address}-kernel_version: {kernel_version}")
    except BaseException as ex:
        print(f"An exception occurred: {ex}")

    try:
        chan.send(b"lsb_release -rs\n")
        ubuntu_version = ""
        while not re.search(prompt, ubuntu_version):
            ubuntu_version += chan.recv(1024).decode(errors="ignore")
        print(f"{ip_address}-kernel_version: {ubuntu_version}")
    except BaseException as ex:
        print(f"An exception occurred: {ex}")

Test code


from concurrent.futures import ThreadPoolExecutor, wait
import time

if __name__ == "__main__":
    tests = [
    ]

    start = time.time()
    for ip, pwd in tests:
        get_kernel_ubuntu_version_raw(ip, pwd)
    end = time.time()
    t1 = end - start

    start = time.time()
    for ip, pwd in tests:
        get_kernel_ubuntu_version(ip, pwd)
    end = time.time()
    t2 = end - start

    start = time.time()
    with ThreadPoolExecutor(max_workers=8) as pool:
        all_task = []
        for ip, pwd in tests:
            task = pool.submit(get_kernel_ubuntu_version_raw, ip, pwd)
            all_task.append(task)
        wait(all_task)
    end = time.time()
    t3 = end - start
    
    start = time.time()
    with ThreadPoolExecutor(max_workers=8) as pool:
        all_task = []
        for ip, pwd in tests:
            task = pool.submit(get_kernel_ubuntu_version, ip, pwd)
            all_task.append(task)
        wait(all_task)
    end = time.time()
    t4 = end - start
    print(t1)
    print(t2)
    print(t3)
    print(t4)

I tried 30 devices.

The original code took 32.69 seconds

send&revc code took 28.23 seconds

ThreadPool code took 6.15 seconds

send&revc&ThreadPool` code took 5.73 seconds

edited Jun 27 at 9:27

answered Jun 11 at 3:23

lei zhang

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6 Comments

parsley72 Jun 15 at 2:41

I tried the first example and "uname -r" works but then "lsb_release -rs" throws an exception Channel is not open. Seems like you can only execute one command per channel? stackoverflow.com/a/28883457/264822

lei zhang Jun 26 at 2:02

This code works well on my pc. chan.exec_command will not close channel, while ssh.exec_command dose.

parsley72 Jun 27 at 4:06

Not what the documentation says docs.paramiko.org/en/stable/api/…

lei zhang Jun 27 at 9:23

Yes you are right. I have changed my answer. And I try to use send&recv instead of exec_command. Time reduced by about 4 seconds from 32.69 to 28.23, but this can be ignored in multi-threading.

parsley72 Jul 1 at 1:44

In the first example where's the multithreading? All youve done is added ssh.set_missing_host_key_policy()

lei zhang Jul 1 at 3:05

multithreading is in Test code ThreadPoolExecutor

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