Verifying a zeroed disk with zerocheck.sh #

#!/bin/bash

# zerocheck.sh - check the beginning, middle, and end of a drive for zeros.
# "when you don't have the time or interest for a full hexdump"

# tested under:
# mac os x 10.6 - 10.10

echo -e "\nzerocheck.sh - check disk for zeros\n"

# check os, display block devices, assign user's choice to variable "DISK2CHK"
if [ "$(uname)" == "Darwin" ]; then
    diskutil list
    echo "Enter disk to check (e.g., /dev/disk2)"
    read DISK2CHK
else
    echo "This script has only been tested under OS X."
    exit 1
fi

# ask for MBs to check, accepting only 1 or greater as valid input, and assign to variable "MB"
MB=0
until [ $MB -ge 1 2>/dev/null ]; do
    echo -e "\nHow many megabytes to check from the beginning, middle, and end of the disk?"
    read MB
done

# convert MBs to bytes and assign to variable "BYTES2CHK"
BYTES2CHK=$((MB * 1048576))

# get the number of bytes via diskutil, stripping leading "(", and assign to variable "BYTES"
BYTES=`diskutil info $DISK2CHK | awk '/Total\ Size/ {sub(/\(/, x); print $5}'`

# let the user know how many bytes the disk has
echo -e "\n$DISK2CHK has" $BYTES "bytes.\n"

# check beginning of disk. (-Ad = decimal; Nx = dump at most x bytes)
echo "The first $BYTES2CHK bytes:"
od -Ad -N$BYTES2CHK $DISK2CHK

# check middle of disk. (-jx = skip x bytes)
echo -e "\n$BYTES2CHK bytes from the middle:"
# divide $BYTES by 2 and assign result to variable "MIDDLEOFDISK"
MIDDLEOFDISK=`expr $BYTES / 2`
od -Ad -j$MIDDLEOFDISK -N$BYTES2CHK $DISK2CHK

# check end of disk:
echo -e "\nAnd the final $BYTES2CHK bytes:"
# subtract BYTES2CHK from BYTES and assign to variable "ENDOFDISK"
ENDOFDISK=$((BYTES - BYTES2CHK))
od -Ad -j$ENDOFDISK $DISK2CHK

#!/bin/bash

# zerocheck.sh - check the beginning, middle, and end of a drive for zeros.
# "when you don't have the time or interest for a full hexdump"

# tested under:
# lubuntu 12.10 (though any distro with util-linux 2.19 or higher should work)

echo -e "\nzerocheck.sh - check disk for zeros\n"

# check os, display block devices, assign user's choice to variable "DISK2CHK"
if [ "$(uname)" == "Linux" ]; then
    lsblk
    echo "Enter disk to check (e.g., /dev/sdc)"
    read DISK2CHK
else
    echo "This script has only been tested under Linux."
    exit 1
fi

# ask for MBs to check, accepting only 1 or greater as valid input, and assign to variable "MB"
MB=0
until [ $MB -ge 1 2>/dev/null ]; do
    echo -e "\nHow many megabytes to check from the beginning, middle, and end of the disk?"
    read MB
done

# convert MBs to bytes and assign to variable "BYTES2CHK"
BYTES2CHK=$((MB * 1048576))

# get the number of bytes via lsblk and assign to variable "BYTES"
BYTES=`lsblk -b $DISK2CHK | awk 'NR==2 {print $4}'`

# let the user know how many bytes the disk has
echo -e "\n$DISK2CHK has" $BYTES "bytes.\n"

# check beginning of disk. (-Ad = decimal; Nx = dump at most x bytes)
echo "The first $BYTES2CHK bytes:"
od -Ad -N$BYTES2CHK $DISK2CHK

# check middle of disk. (-jx = skip x bytes)
echo -e "\n$BYTES2CHK bytes from the middle:"
# divide $BYTES by 2 and assign result to variable "MIDDLEOFDISK"
MIDDLEOFDISK=`expr $BYTES / 2`
od -Ad -j$MIDDLEOFDISK -N$BYTES2CHK $DISK2CHK

# check end of disk:
echo -e "\nAnd the final $BYTES2CHK bytes:"
# subtract BYTES2CHK from BYTES and assign to variable "ENDOFDISK"
ENDOFDISK=$((BYTES - BYTES2CHK))
od -Ad -j$ENDOFDISK $DISK2CHK