====== Disks ======

===== Overwrite empty space with nulls =====

Write Write nulls to free space of all partitions on /dev/sda

<file bash cleandisk>
#!/bin/bash
## fill empty space with nulls to really delete everything

sfdisk -d /dev/sda \
| awk '/^.dev.sd/ {print $1}' \
| while read d; do
    mkdir -p /mnt/x
    mount $d /mnt/x
    ls -l /mnt/x
    echo "writing nulls to free space on $d ..."
    time cat /dev/zero > /mnt/x/zeroes
    sync
    rm /mnt/x/zeroes
    umount /mnt/x
  done
echo OK
</file>

===== ddrescue =====

<code bash>
disk=/dev/sdx
image=/mnt/temp/sdx.img
log=/mnt/temp/ddrescue-sdx.log

# first pass
ddrescue -f -n $disk "$log" "$image" "$log"

# now retry harder
ddrescue -d -f -r3 $disk "$log" "$image" "$log"
</code>

Options:
  * -d, --idirect : use direct disc access for input file
  * -f, --force : overwrite output device or partition
  * -n, --no-scrape : skip the scraping phase
  * -r, --retry-passes=<n> : exit after <n> retry passes (-1=infinity) [0]


{{tag>public linux}}