#!/bin/bash
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#                                                                                            #
# Author: Andreas Maus <maus@ypbind.de> / Snel.com - Yavuz Aydin                             #
# E-mail: support@snel.com                                                                   #
# (c) Snel.com - all rights reserved                                                         #
#                                                                                            #
##############################################################################################
#                                                                                            #
# Script: check_reboot-required                                                              #
# License: This file is licensed under the GPLv3 License                                     #
# Purpose: Check if reboot is required                                                       #
# Tested on: CentOS 6/7/8, CloudLinux 7, Debian 7/8/9/10 and Ubuntu 16.04/18.04/20.04        #
#            Proxmox 6                                                                       #
# CentOS 8 needs yum-utils installed!
#                                                                                            #
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#                                                                                            #
# Changelog:                                                                                 #
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#                                                                                            #
# 2021/01/07  1.0  First release                                                             #
#                                                                                            #
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APPNAME=`basename $0`

# Defining standard messages and exit error levels
# https://nagios-plugins.org/doc/guidelines.html
OK_EXIT_CODE=0
WARNING_EXIT_CODE=1
CRITICAL_EXIT_CODE=2
UNKNOWN_EXIT_CODE=3
OK_MSG="OK"
WARNING_MSG="Warning"
CRITICAL_MSG="Critical"
UNKNOWN_MSG="Unknown"

# Using Unknown as default
EXIT_CODE=$UNKNOWN_EXIT_CODE
EXIT_MSG=$UNKNOWN_MSG

warn_only="false"

which lsb_release 2>/dev/null >/dev/null
if [ $? -ne 0 ]; then
  echo "lsb_release is missing"
  exit ${UNKNOWN_EXIT_CODE}
fi

function usage() {
  cat - <<EOF
Usage: ${APPNAME} [-w|--warn] [-h|--help]

This check command checks if a reboot are required after an upgrade. It will
also list packages that requires a reboot to ease the decision for the
sysadmin if/when a reboot needs to be carried out.

 -h, --help
    Show this help
 -w, --warn
    Report warning (instead of a critical) condition if reboot is required
EOF
}

case $1 in
  -w|--warn)
    warn_only="true"
    ;;
  -h|--help)
    usage
    exit ${OK_EXIT_CODE}
    ;;
esac

function check_debian() {
  if [ -s /var/run/reboot-required ]; then
    if [ -s /var/run/reboot-required.pkgs ]; then
      packages=$(xargs < /var/run/reboot-required.pkgs)
    else
      packages=""
    fi
    if [ -z "${packages}" ]; then
      EXIT_MSG_BODY="System reboot is required"
      if [ "${warn_only}" == "true" ]; then
        EXIT_MSG=${WARNING_MSG}
        EXIT_CODE=${WARNING_EXIT_CODE}
      else
        EXIT_MSG=${CRITICAL_MSG}
        EXIT_CODE=${CRITICAL_EXIT_CODE}
      fi
    else
      EXIT_MSG_BODY="System reboot is required by: ${packages}"
      if [ "${warn_only}" == "true" ]; then
        EXIT_MSG=${WARNING_MSG}
        EXIT_CODE=${WARNING_EXIT_CODE}
      else
        EXIT_MSG=${CRITICAL_MSG}
        EXIT_CODE=${CRITICAL_EXIT_CODE}
      fi
    fi
  else
    check_running_kernel
  fi
}

function check_redhat() {
  major=$(lsb_release -rs | cut -d '.' -f 1)

  if [ ${major} -lt 7 ]; then
    check_running_kernel
  fi

  output_clean=$(needs-restarting -r | xargs)
  output=$(needs-restarting -r)
  if [ $? -eq 0 ]; then
    echo "No reboot required: ${output_clean}"
    exit ${OK_EXIT_CODE}
  elif [ $? -eq 1 ]; then
    EXIT_MSG_BODY="${output_clean}"
    if [ "${warn_only}" == "true" ]; then
      EXIT_MSG=${WARNING_MSG}
      EXIT_CODE=${WARNING_EXIT_CODE}
    else
      EXIT_MSG=${CRITICAL_MSG}
      EXIT_CODE=${CRITICAL_EXIT_CODE}
    fi
  fi
}

function check_running_kernel() {
  newest_installed_kernel=`ls -t /boot/vmlinuz-* | sed "s/\/boot\/vmlinuz-//g" | head -n1`
  running_kernel=`uname -r`
  if [[ $newest_installed_kernel != $running_kernel ]]; then
    EXIT_MSG_BODY="System reboot is required by: newer kernel (${newest_installed_kernel}) is available, running kernel is ${running_kernel}"
    if [ "${warn_only}" == "true" ]; then
      EXIT_MSG=${WARNING_MSG}
      EXIT_CODE=${WARNING_EXIT_CODE}
    else
      EXIT_MSG=${CRITICAL_MSG}
      EXIT_CODE=${CRITICAL_EXIT_CODE}
    fi
  else
    echo "No reboot required"
    exit ${OK_EXIT_CODE}
  fi
}

distro=$(lsb_release -is)
case "${distro}" in
  Debian|Ubuntu)
    check_debian
    ;;
  CentOS|CloudLinux)
    check_redhat
    ;;
  *)
    echo "Unsupported distribution ${distro}"
    exit ${UNKNOWN}
    ;;
esac

# Echo message and exit
echo "${EXIT_MSG}: ${EXIT_MSG_BODY}"
exit $EXIT_CODE