Linux zero filesystem bash script

This is a short linux bash script I wrote that’s adequate for zero’ing a filesystem for on-premise server storage.

Note that the only “secure erase” is to destroy the physical drive because of various internal disk-level caches.

To do multiple passes (in this case 10 passes):

# seq 1 10 | xargs ./zero.sh

#!/bin/bash

# Program: zero.sh
# Purpose: write on pass of zeros in free space on current volume. 
# Date: 2017 10 28
# Author: James Briggs, USA
# Usage: cd "filesystem"; screen ./zero.sh
# Env: CentOS 6,7 bash
# Notes:
#   This program is write-intensive, so not recommended for SSD or Flash drives unless disk wear is ok
#   This is not a secure erase, but is ok for on-premise storage.

outfile=zero
sz=1G
delay=0

n=1
err=""

# cleanup after previous runs
/bin/rm -f *.zero.bin "$0.out"
/bin/sync

# while [ "$n" -le "4" ]; do
while true; do
   /bin/echo "$0: writing chunk #$n of $sz ..."
   /bin/dd if=/dev/zero of="$outfile-$n.zero.bin" oflag=nocache bs=$sz count=1 conv=fsync || let err="yes"
   /bin/echo "$0: syncing chunk #$n of $sz ..."
   /bin/sync

   [ -n "$err" ] && break

   sleep $delay
   let n++
done

/bin/echo "$0: deleting $n chunks of $sz ..."
/bin/rm *.zero.bin

/bin/echo "$0: syncing filesystem after chunk deletions ..."
/bin/sync

msg="done zeroing current volume with $n chunks of $sz."
/bin/echo "$0: $msg"
/bin/echo "$0: `/bin/date` $msg" > "$0.out"

exit 0

A one-line log file is written:

# cat zero.sh.out
./zero.sh: Sun Oct 29 04:16:30 UTC 2017 done zeroing current volume with 12 chunks of 1G.

github: redeemer