dd question

[Warren Block]

On Mon, 28 Sep 2015, Polytropon wrote:

> On Sun, 27 Sep 2015 19:00:47 -0600 (MDT), Warren Block wrote:
>> On Sun, 27 Sep 2015, William A. Mahaffey III wrote:
>>
>>> If I use disklabel to add a 'd' slice, will that mess up what is already
>>> there ? What is the syntax for that, I don't see it in the disklabel/bsdlabel
>>> man page ? The man page for disklabel/bsdlabel shows a way to initialize a
>>> whole disk using 'fdisk -BI <dev>' & implies that this will create a 'da0s1'
>>> slice in the process. However it will also wipe out what is already there. If
>>> I do that, can I then copy the img-file contents in some way ? Thanks & TIA
>>> :-) ....
>>
>> Please stop using fdisk and bsdlabel.  gpart(8) does everything they do
>> and is easier to use.
>
> But it works so nicely, especially for all the many
> non-standard settings! :-)
>
> Sure, gpart (and in a related context, GPT) is the
> way to go for 99% of use cases. Somehow I still like
> the ability to ditch partitioning at all and just
> newfs a device, or make a "one big bootable partition"
> with two bsdlabel commands. This knowledge will soon
> go down the drain, together with other "old craft"
> of UNIX skills many decades old. :-)

You can still put a filesystem on a raw device, and gpart will happily 
create bsdlabels.  It is a general-purpose partitioning tool, and can 
write at least half a dozen partitioning schemes including bsdlabel and 
MBR.  It uses the same type of commands regardless of the partitioning 
scheme.

> As the installation image is best dealt with bsdlabel,
> resizing 'c' and adding a 'd' partition should be possible,
> with the commands run through a mdconfig'ured virtual
> node connected to the image file. As I said, I haven't
> tried this, but it's probably possible. In worst case,
> it's a "try & fail" issue. :-)

Try it with gpart.  Consider it a test to see if gpart really is a 
replacement for bsdlabel.