How to change a Linux user password from python

Question

I\'m having problems with changing a Linux user\'s password from python. I\'ve tried so many things, but I couldn\'t manage to solve the issue, here is the sample of things

Answer 1

I ran accross the same problem today and I wrote a simple wrapper around subprocess to call the passwd command and feed stdin with the new password. This code is not fool proof and only works when running as root which does not prompt for the old password.

import subprocess
from time import sleep

PASSWD_CMD='/usr/bin/passwd'

def set_password(user, password):
    cmd = [PASSWD_CMD, user]
    p = subprocess.Popen(cmd, stdin=subprocess.PIPE)
    p.stdin.write(u'%(p)s\n%(p)s\n' % { 'p': password })
    p.stdin.flush()
    # Give `passwd` cmd 1 second to finish and kill it otherwise.
    for x in range(0, 10):
        if p.poll() is not None:
            break
        sleep(0.1)
    else:
        p.terminate()
        sleep(1)
        p.kill()
        raise RuntimeError('Setting password failed. '
                '`passwd` process did not terminate.')
    if p.returncode != 0:
        raise RuntimeError('`passwd` failed: %d' % p.returncode)

If you need the output of passwd you can also pass stdout=subprocess.PIPE to the Popen call and read from it. In my case I was only interested if the operation succeeded or not so I simply skipped that part.

Security consideration: Do not use something like echo -n 'password\npassword\n | passwd username' as this will make the password visible in the process list.

SUDO

Since you seam to want to be using sudo passwd I would recommend adding a new line to your /etc/sudoers (use visudo for that!)

some_user ALL = NOPASSWD: /usr/bin/passwd

Sudo will not ask for the password for some_user and the script will run as expected.

Alternatively simply add an extra p.stdin.write(u'%s\n' % SUDO_PASSWORD) line. That way sudo will receive the user password first and then passwd receives the new user password.