#!/bin/bash

PATH=$PATH:/sbin

[ "$TERM" = "dumb" -a ! -t 0 ] && run=cron || run=local
[ "`ps --no-headers o comm $PPID`" = "sshd" ] && run=SSH

debug=0
[ "$run" = "SSH" ] && debug=1
[ "$run" = "local" ] && debug=2

recipient=username

# Add increment1% if we're above threshold1%, but add increment2% if we're above threshold2% full

threshold1=85
increment1=5

threshold2=90
increment2=10

[ -n "$1" ] && debug=$1

# Scan for all Volume Groups

vgs --noheadings | tr -s ' ' | cut -d' ' -f2 | while read vg
do
  [ "$debug" -gt "0" ] && echo "Checking Volume Group $vg"
# Scan for Logical Volumes in each Group
  lvs --noheadings $vg | tr -s ' ' | cut -d' ' -f2 | while read lv
  do
    [ "$debug" -gt "0" ] && echo "Checking Logical Volume $lv"
# Check if LV is mounted
    percent=`df -h | grep "/dev/mapper/$vg-$lv " | sed 's/.* \([0-9]\+\)%.*/\1/'`
    if [ -n "$percent" ]
# Yes we have a mounted LV
    then
      [ "$debug" -gt "0" ] && echo "Logical Volume $vg/$lv is mounted and is $percent% full"
# Is it more than threshold1% full?
      if [ "$percent" -gt "$threshold1" ]
      then
# Add increment1% if we're above threshold1%, but add increment2% if we're above threshold2% full
        incr=$increment1
        [ "$percent" -gt "$threshold2" ] && incr=$increment2
        if ps ax | grep -v grep | grep -q "resize2fs /dev/mapper/$vg-$lv "
        then
          echo "resize operation already running" | mail -s "Would increase /dev/$vg/$lv by $incr%" $recipient
        else
          ( time ( df -h | grep "/dev/mapper/$vg-$lv "; echo; lvextend -l +$incr%LV -r /dev/$vg/$lv 2>&1; df -h | grep "/dev/mapper/$vg-$lv "; echo; vgs ) ) |& mail -s "Increasing /dev/$vg/$lv by $incr%" $recipient
        fi
      else
        [ "$debug" -gt "0" ] && echo "Partition is ${percent}% full" | mail -s "/dev/$vg/$lv does not need extending at present." $recipient
      fi
    else
      [ "$debug" -gt "0" ] && echo "Logical Volume $vg/$lv is not mounted"
    fi
  done
done