#!/bin/bash
#
#    Copyright P.S. Computer Services Ltd 2014
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
#    This is a Nagios plugin to be used on dpkg/deb based Linux hosts.  
#    e.g. Debian, Ubuntu etc
#    It determines whether the running kernel is up to date with the installed kernels,
#    or whether the host has a mis-matching kernel.  i.e. the host needs a reboot.
#    Please note that if you haven't installed the latest kernel via apt or aptitude
#    then this will not be flagged up.  You shoudl also run a Nagios plugin that 
#    looks for packages that need upgrading.


# Nagios plugin exit codes
OK=0;
#WARNING=1;
CRITICAL=2;
#UNKNOWN=3;


LATEST_KERNEL=$(dpkg-query --search vmlinuz-* | sort | tail -1 | cut -d " " -f1 | sed 's/://g' | sed 's/linux-image-//g')

RUNNING_KERNEL=$(uname -r)

if [ "$LATEST_KERNEL" = "$RUNNING_KERNEL" ]; then
  echo "OK - Running kernel ( $RUNNING_KERNEL ) = most recent on disk kernel ( $LATEST_KERNEL )"
  exit $OK
else
  echo "CRITICAL - Reboot required. Running kernel $RUNNING_KERNEL is too old, newest kernel on disk is $LATEST_KERNEL"
  exit $CRITICAL
fi