Re: [tlug] formatting HDD leaves 11.7 GB untouched

[Christian Horn <chorn@example.com>]

Hoi Thomas,

On Mon, Dec 02, 2019 at 10:48:19AM +0900, Thomas Blasejewicz wrote:
> I have a 160 GB HDD that was used in an old notebook running Mint 19.2,
> using only one partition.
> Since I changed the HDD, I would like to use this one for external storage.
> So .. I formatted the disk; the usual way; using ext4

'formatting' could mean multiple things:
- overwriting all blocks
- and/or just generating fresh filesystem structures 

> Afterwards, the properties showed: 8.1 GB used
> Looking at it with "disks" I get: 160 GB -> 156 GB free; 2.3% used.

Maybe you have a further partition on the disk?
A filesystem takes up also some space by itself, but here where I
tried to replicate your issue much less than 4GB:

[root@kosmos ~]# cat /proc/partitions 
major minor  #blocks  name
[..snip..]
   7        0  167772160 loop0
[root@kosmos ~]# 
[root@kosmos ~]# df -h /mnt/tmp/
Filesystem      Size  Used Avail Use% Mounted on
/dev/loop0      157G   61M  149G   1% /mnt/tmp
[root@kosmos ~]# 

This is a filesystem plainly on a 160GB block device, no partitions.


> That means, if I understand that correctly, the disk still holds 11.7 GB of
> something that I do not need.

'cat /proc/partitions' should tell us if there is more than one
partition on the disk.


> How can I wipe the disk ENTIRELY clean?

A 'mkfs.ext4' is just creating data structures, if you want to 
overwrite the disk with zeros then 'cat /dev/zero >/dev/<diskdevice>'
could do that.

cheers,
Chris