Re: how to remove freebsd when it is running

On Wednesday, 17 April 2024 at 22:21:15 +0800, hlyg wrote:

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> my freebsd 13 is installed at flash disk of dell thin client
>
> it doesn't work well, i want to remove it
>
> "dd if=/dev/zero of=/dev/ada0 count=1000 ..." doesn't work, freebsd doesn't
> allow

Yes, this is a feature, not a bug.  As others have observed, this is
akin to sawing off the branch that you're sitting on.

Next month will be 25 years since I addressed this in “The Complete
FreeBSD” (http://www.lemis.com/grog/Documentation/CFBSD/book.pdf.gz,
page 117):

  How to uninstall FreeBSD

  What, you want to remove FreeBSD? Why would you want to do that?

  Seriously, if you decide you want to completely remove FreeBSD from
  the system, this is no longer a FreeBSD issue, it's an issue of
  whatever system you use to replace it. For example, on page 63 we
  saw how to remove a Microsoft partition and replace it with FreeBSD;
  no Microsoft software was needed to remove it. In the same way, you
  don't need any help from FreeBSD if you want to replace it with a
  different operating system.

That's still the simplest way to do it, but it is possible to shoot
yourself in the foot the way you are trying to do.  For that you need
to set bits in the sysctl sysctl kern.geom.debugflags.  Set it to 16
and it will happily let you destroy your disk contents.  See
http://www.lemis.com/grog/diary-jul2015.php?subtitle=Recovering%20the%20Microsoft%20box&article=D-20150725-014511#D-20150725-014511
for a blow-by-blow description.

> according to dell manual, i shall be able to enter bios by pressing
> F2 before bsd booting so that i can set boot sequence  to boot from
> usb disk, but i can't enter bios, pressing F2 doesn't work

This is clearly not a FreeBSD issue.

Greg
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