Script to remove client's dhcp reservation

• Intro
• Script

Intro

Script

#!/some-path/python3
"""
    The script to remove DHCP reservation
"""

import os
import sys
import socket
import argparse
import click
import re
import subprocess
import platform
from colorama import Fore, Back, Style
import getpass
from time import gmtime, strftime
import datetime
import logging, logging.handlers


def not_whq_pls():
    """
    Check that script is not used on DHCP in WHQ and PLS.
    Colorama help
    Fore: BLACK, RED, GREEN, YELLOW, BLUE, MAGENTA, CYAN, WHITE, RESET.
    Back: BLACK, RED, GREEN, YELLOW, BLUE, MAGENTA, CYAN, WHITE, RESET.
    Style: DIM, NORMAL, BRIGHT, RESET_ALL

    """
    if socket.gethostname() == "hq-infra1.???.com" or socket.gethostname() == "pls-infra1.???.com":
        sys.exit(Back.RED + Fore.YELLOW + Style.BRIGHT + 'Error: this cannot be run on WHQ/PLS DHCP servers, please file request via our Bugzilla.' + Style.RESET_ALL)

# Make sure this is not run on whq/pls dhcp servers. 
not_whq_pls()

# define logging directory structure
PROGRAM = os.path.basename(sys.argv[0])   # name of this script
LOG_PATH = ("/var/log/" + PROGRAM)        # put together "/var/log/"
if not os.path.exists(LOG_PATH):          # create LOG_PATH if doesn't exists
    os.makedirs(LOG_PATH)
    os.chown(LOG_PATH,-1,580)       # root(-1 means no change):crm
    os.chmod(LOG_PATH,0o775)               # drwxrwxr-x

parser = argparse.ArgumentParser(
                                description="Delete DHCP reservation (not for WHQ and PLS)")
parser.add_argument("-s", "--system", help="System's name", required=True)
args = parser.parse_args()
system=args.system

# --- Define logging
LOG_FILE = (LOG_PATH + "/" + system + "_" + datetime.datetime.now().strftime("%m-%d-%Y_%Hh%Mm%Ss"))
# create logger (interface that script uses for logging)
logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)
# create file handler (define log destination)
handler = logging.handlers.TimedRotatingFileHandler(LOG_FILE, when='MIDNIGHT', backupCount=100, utc=False)
# create formatter (define layout of logs)
formatter = logging.Formatter('%(asctime)s:%(levelname)s: %(message)s')
handler.setFormatter(formatter)
# add handler to logger
logger.addHandler(handler)

def who_run_script():
    i_am=getpass.getuser()
    if i_am != "root":
        logger.debug(i_am + ", please run this via sudo, exiting")
        sys.exit(i_am + ", please run this via sudo, exiting")


def dhcp_cfg_check():
    """
    Check DHCP cfg syntax, ol678
    """
    if re.match("6.*", platform.dist()[1]):
        logger.debug("Check DHCP config for OL6")
        return True if subprocess.call(['service', 'dhcpd', 'configtest']) == 0 else False
    else:
        logger.debug("Check DHCP config for OL[78]")
        return True if subprocess.call(['dhcpd', '-t']) == 0 else False 

def dhcp_restart():
    """
    Restart DHCP service, ol678
    """
    if re.match("6.*", platform.dist()[1]):
        logger.debug("OL6 DHCP service restart")
        return True if subprocess.call(['service', 'dhcpd', 'restart']) == 0 else False
    else:
        logger.debug("OL[78] DHCP service restart")
        return True if subprocess.call(['systemctl', 'restart', 'dhcpd']) == 0 else False

def del_reservation():
    path_system="/etc/dhcp/clients/" + system
    if os.path.exists(path_system):
        os.remove(path_system)
        logger.debug("Removed reservation for " + path_system)
        print("Removed reservation for " + path_system)
    else:
        logger.debug(path_system + " doesn't exist. Is another name used for reservation? ")
        sys.exit(path_system + " doesn't exist. Is another name used for reservation? ")

def refresh_clients_include():
    """ Refresh clients.include file """
    CLNTDIR = "/etc/dhcp/clients/"

    if not os.path.exists(CLNTDIR):
        logger.debug("ERROR: " + CLNTDIR + " does not exist.")
        sys.exit("ERROR: " + CLNTDIR + " does not exist.")

    f = open("/etc/dhcp/clients.include", "w+")
    try:
        for root, dirs, files in os.walk(CLNTDIR):
            for clientname in files:
                f.write("include \"" + CLNTDIR + clientname + "\" ;\n")
        logger.debug("OK: Compiled new /etc/dhcp/clients.include")
        print("OK: Compiled new /etc/dhcp/clients.include")
    except:
        logger.debug("ERROR: cannot compile /etc/dhcp/clients.include")
        sys.exit("ERROR: cannot compile /etc/dhcp/clients.include")
    f.close()


# ---- MAIN -----
if __name__ == '__main__':
    # start logging
    logger.debug("")
    logger.debug("Start at: " + strftime("%a, %d %b %Y %H:%M:%S", gmtime()))
    who_run_script()
    if click.confirm('Do you really want to remove reservation for %s?' % system):
        del_reservation()
        refresh_clients_include() 
        dhcp_cfg_check()
        dhcp_restart()        
    logger.debug("Finish at: " + strftime("%a, %d %b %Y %H:%M:%S", gmtime()))
sys.exit(0)