LinuxDNSChange

import re
from netmiko import ConnectHandler
from netmiko.ssh_exception import NetMikoTimeoutException
from paramiko.ssh_exception import SSHException
from netmiko.ssh_exception import AuthenticationException


def main_def():
    username = input("Enter your username: ")
    password = input("Enter you password:  ")
    dns = str(input("Enter DNS server: "))

    with open('devices') as f:
        devices_list = f.read().splitlines()

    for d in devices_list:
        linux = {
            'device_type': 'linux',
            'ip': str(d),
            'username': str(username),
            'password': str(password),
            'port': 22,
            'verbose': True
        }
        print("*" * 80, "\n")
        try:
            connection = ConnectHandler(**linux)
        except NetMikoTimeoutException:
            print("*" * 100)
            print(f'Timeout to device {d}:')
            continue
        except AuthenticationException:
            print("*" * 100)
            print(f'Authentication failure device {d}:')
            continue
        except SSHException:
            print("*" * 100)
            print(f'SSH Issue. Are you sure SSH is enabled device {d}')
            continue
        except Exception as unknown_error:
            print("*" * 100)
            print(f'Other error device {d} : ' + str(unknown_error))
            continue
        pass
        output = connection.send_command('cat /etc/resolv.conf')
        ip = re.search(r"\b(?:[0-9]{1,3}\.){3}[0-9]{1,3}\b", output)
        parsedint = ip.group(0)
        print("*" * 80, "\n")
        print("Contains of etc/resolf.conf: \n ")
        output = connection.send_command('cat /etc/resolv.conf')
        print(output)
        if parsedint != dns:
            print("incorect DNS entry")
            print(parsedint)
            print("*" * 80, "\n")
            change = (input("Do you wish to change the entry? : Y/N "))
            if change == "Y" or change == "y":
                change_dns = connection.send_command(f"sed -i 's/{parsedint}/{dns}/g' /etc/resolv.conf")
                print("DNS Entry changed")
                output = connection.send_command('cat /etc/resolv.conf')
                print(output, "\n")
            else:
                print("System exit")
        else:
            print("*" * 80, "\n")
            print("DNS entry is correct")


if __name__ == "__main__":
    main_def()