Script to easily enable netconsole and change kernel verbosity

netconsole.sh

#!/usr/bin/env bash

########
# Script to easily enable netconsole and change kernel verbosity
#
# See http://elinux.org/Debugging_py_printing
#

set -e

declare -A VERBOSITY
VERBOSITY[0]=KERN_EMERG
VERBOSITY[1]=KERN_ALERT
VERBOSITY[2]=KERN_CRIT
VERBOSITY[3]=KERN_ERR
VERBOSITY[4]=KERN_WARNING
VERBOSITY[5]=KERN_NOTICE
VERBOSITY[6]=KERN_INFO
VERBOSITY[7]=KERN_DEBUG

DEV=""
HOST=""
LEVEL=7

function HELP {
    echo "Usage: $(basename $0) [@dev] <ip address> [verbosity]"
    echo
    echo "Accepted numeric verbosity levels are:"
    for i in "${!VERBOSITY[@]}"; do
        echo "    $i (${VERBOSITY[$i]})"
    done
}

function ERROR {
    echo $1
    HELP
    exit $2
}

function ERRORMISSINGARGS {
    ERROR "Missing required arguments." 1
}

if [[ $# -eq 0 ]]; then ERRORMISSINGARGS; fi
if [[ $1 == "@"* ]]; then DEV=${1:1}; shift; fi

if [[ $# -eq 0 ]]; then ERRORMISSINGARGS; fi
HOST=$1
IP=$(getent ahostsv4 "$HOST" | grep STREAM | cut -f1 -d' ')
shift

if [[ $# -gt 0 ]]; then LEVEL=$1; shift; fi

if [[ $# -gt 0 ]]; then 
    ERROR "Too many arguments encountered." 2
fi

if [[ ! " ${!VERBOSITY[@]} " =~ " $LEVEL " ]]; then
    ERROR "Unknown verbosity level." 3
fi

if [[ "$DEV" == "" ]]; then 
	DEV=$(ip route show to match "$IP" | grep -o "dev .*" | cut -f2 -d' ' | head -n1)
fi

echo "Please run \`netcat -u -l 6666\` on the target machine at $IP now."
echo "Press <Enter> when ready..."
read

OLDLEVEL=$(cut -f1 /proc/sys/kernel/printk)
echo "Increasing console verbosity to from $OLDLEVEL (${VERBOSITY[$OLDLEVEL]}) to $LEVEL (${VERBOSITY[$LEVEL]})"
echo $LEVEL > /proc/sys/kernel/printk

echo "Sending console output via UDP from interface ${DEV} to $IP:6666"
modprobe -r netconsole
modprobe netconsole netconsole=@/${DEV},@${IP}/

echo
echo "You should now see logs appearing on the target machine. If not,"
echo "please verify the target machine's IP address is ${IP} and"
echo "that no firewalls are blocking traffic."