Re: Wiping a disk partition

On 25/06/2025 15:28, Tomek CEDRO wrote:
> On Wed, Jun 25, 2025 at 12:18 PM Odhiambo Washington <odhiambo@gmail.com> wrote:
>> I have this:
>> ```
>> root@gw:/home/wash # df -h
>> Filesystem     Size    Used   Avail Capacity  Mounted on
>> /dev/ada0p2    1.8T    552G    1.1T    33%    /
>> devfs          1.0K      0B    1.0K     0%    /dev
>> fdescfs        1.0K      0B    1.0K     0%    /dev/fd
>> procfs         8.0K      0B    8.0K     0%    /proc
>> linprocfs      8.0K      0B    8.0K     0%    /compat/linux/proc
>> linsysfs       8.0K      0B    8.0K     0%    /compat/linux/sys
>> /dev/ada1p2    1.8T    856G    802G    52%    /disk2
>> ```
>>
>> What is the fastest way to wipe all data on /dev/ada1p2?
> The fastest way would be to overwrite partition with zeros:
>
> dd if=/dev/zero of=/dev/ada1p2 bs=1g status=progress
>
> In order to overwrite data safely so these are not easily recovered
> you can use /dev/random in several overwrite loops, then in the last
> iteration you can use /dev/zero to mark partition clean (or leave
> random data for someone to wonder). Note /dev/random is much slower
> than /dev/zero.
>
> You may also use badblocks utility in destructive-write test to
> overwrite with different patterns and check disk condition at the same
> time but this will be slowest solution :-)
>
> https://man.freebsd.org/cgi/man.cgi?query=badblocks
>
> Have fun :-)

Right answer!  As a refinement you might want to umount the volume first 
to avoid stability problems.

The question was how to wipe the data on a partition. Some people have 
suggested secure erasing the entire drive. You cannot issue a SCSI 
command to erase a software defined partition that SCSI doesn't know 
anything about. Deleting the files or creating a new FS doesn't wipe the 
file contents. Without additional context, overwriting the partition 
with zeros is the best answer.

Except... given that the partition IS mounted it presumably has 852Gb of 
files, and the real question might have been how to delete all the files 
in the /disk2 directory rather the wiping the partition- so Tomek - why 
do you ask?

Regards, Frank.