[CentOS] erasing a disk

Mon Sep 14 20:52:18 UTC 2020
Robert Heller <heller at deepsoft.com>

At Mon, 14 Sep 2020 13:14:44 -0700 CentOS mailing list <centos at centos.org> wrote:

> Folks
> I've encountered situations where I want to reuse a hard-drive.  I do 
> not want to preserve anything on the drive, and I'm not concerned 
> about 'securely erasing' old content.  I just want to be able to 
> define it as an Physical Volume (in a logical volume set), or make it 
> a ZFS disk, or sometimes make it a simple EXT3, ExFAT or NTFS 
> disk.  However, old 'signatures' get in the way and Linux sometimes 
> refuses to let me proceed.  I know that a fool-proof solution is to 
> use the "dd if=/dev/zero bs=32768 oflag=direct" on the disk, but when 
> we're talking USB-connected hard drives of 8 TB, that's an operation 
> that can take days.
> The disk in question might even have been corrupted.  This would make 
> using 'zpool destroy' to clear out a ZFS disk, or
> I've tried erasing the first megabyte of the disk, but there are ZFS 
> or LVM structures that get in the way.  So, does anyone have an 
> efficient way to erase structures from a disk such that it can be reused?
> Something like
>    -erase first N blocks (block defined as 4096)
>    - Erase <number> blocks starting at block <number>
>    - erase last <number> blocks

Use dd in a script:

# erase N 4K blocks starting at M
# (M=0 means from the start of the disk)
# usage: $0 start4Kblock numberof4Kblocks drive
M = $1
N = $2
rawdisk = $3
dd if=/dev/zero bs=4096 oflag=direct count=$N seek=$M of=$rawdisk

> At least such an algorithm would be quicker than erasing 8 TB of data.
> David
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