[Nagios check, Linux] Check if physical disk size is bigger enough than total size of it's logical partitions (helps to identify partitions which could be extended with resize2fs util)

check_partition_need_to_be_resized.sh

#!/bin/bash

set -e

OK=0
WARN=1
CRIT=2
UNKNOWN=3

SENSITIVITY_THRESHOLD_PERCENTS=10

function bytes_to_gb {
  result=`echo "scale=3;$1/1024/1024/1024"|bc`
  printf ${result}
}

IFS=$'\n'
for disk_info in `lsblk -bn | grep -v ─ | grep disk`; do
  disk_name=`echo "$disk_info" | awk '{print $1}'`
  disk_size_bytes=`echo "$disk_info" | awk '{print $4}'`
  
  # Calculate total partitions size for current disk
  total_partitions_size_bytes=0
  for partition_info in `df -a | tail -n +2 | grep $disk_name | awk '{print $1,$2,$3,$4,$5}' | sort | uniq`
  do
    partition_size=`echo "$partition_info" | awk '{print $2}'`
    if [[ "$partition_size" == ?(-)+([0-9]) ]]; then
      total_partitions_size_bytes=$(( total_partitions_size_bytes + partition_size * 1024 ))
    fi
  done

  difference_bytes=$(( disk_size_bytes - total_partitions_size_bytes ))

  disk_size_gb=`bytes_to_gb $disk_size_bytes`
  total_partitions_size_gb=`bytes_to_gb $total_partitions_size_bytes`
  difference_gb=`bytes_to_gb $difference_bytes`

  #echo "[/dev/$disk_name] disk phisical size ${disk_size_gb}GB, total partitions size is ${total_partitions_size_gb}GB"
  #echo "Difference is $(( difference_bytes * 100 / disk_size_bytes )) percents"

  if (( difference_bytes * 100 / disk_size_bytes > SENSITIVITY_THRESHOLD_PERCENTS )); then
    echo "CRITICAL - one or more partitions at /dev/$disk_name needs to be extended (phisical disk size is ${disk_size_gb}GB, but total size of it's partitions is ${total_partitions_size_gb}GB). Use 'sudo resize2fs /dev/${disk_name}[1-9]' to fix"
    exit $CRIT
  fi
done

echo "OK - no partitions needs to be resized"
exit $OK