Re: [Gptfdisk-general] misreads NetBSD as FreeBSD

[Rod S. <rod...@ro...>]

On 8/3/23 19:58, David Chmelik wrote:
> On 8/3/23 6:59 AM, Rod Smith wrote:
>> On 8/3/23 04:31, dch...@gm... wrote:
>>> Lately I also use gdisk, etc.  Unlike fdisk, gdisk misreads my NetBSD 
>>> partition as a FreeBSD one.
>>
>> There's a lot you haven't stated that's likely relevant. For instance, 
>> is the disk currently MBR or GPT? If the latter, was it once MBR, but 
>> was converted to GPT; and if so, by what program? Is the fdisk you're 
>> using from util-linux or based on libparted? What column(s) of output 
>> are you reading in both fdisk and gdisk? Because I don't know the 
>> answers to these questions, I can't give you an answer about what's 
>> going on; however, I can say this....
> I guess everything's fine then.  The solid state drive (SSD/M2/NVME) is 
> currently MBR and I used fdisk from util-linux but also used it on *BSD 
> UNIX (which works differently).

Yes, if the disk is MBR, then what you're seeing is the expected 
behavior, caused by the fact that there is (AFAIK) no direct GPT 
correlate to the MBR 0xA9 type code. GPT fdisk does the same thing with 
a number of type codes for NTFS and several FAT variants; they all get 
compressed down to GPT fdisk's 0700.

> Thanks.  I'd more likely reinstall everything on that drive if I had a 
> reason to convert to GPT, but I aliased fdisk to gdisk

I STRONGLY recommend against doing this. Although I modeled gdisk's user 
interface on that for Linux fdisk, as this exchange has shown, gdisk is 
not completely compatible. I'd be especially worried about scripts that 
might try to parse fdisk's output, get it wrong, and do something 
disastrous as a result. Also, if you launch gdisk on an MBR disk and 
accidentally type "w", the result will be that the MBR partition table 
will be replaced by a GPT, which could cause serious problems.

> because when I 
> got two new 16TB WD/HGST hard disc drives and used fdisk on them, it 
> seemed they were broken, and I didn't want to accidentally try a third.
> Likely it wasn't fdisk causing it rather than just some decrease in 
> quality and a chance I got two bad ones.  However now I type fdisk 
> (gdisk) or /sbin/fdisk (the real fdisk).

Disk partitioning tools, including fdisk, gdisk, and parted, are 
unlikely to physically damage a disk. The worst they might do is to 
damage the partition table, or perhaps the contents of a partition. This 
is bad enough, of course, but it won't send a disk to a trash can; the 
disk should still be usable, after restoring it from a backup or using 
low-level recovery tools like PhotoRec.

That said, if you distrust util-linux's fdisk, you could try replacing 
it with GNU fdisk (https://directory.fsf.org/wiki/Fdisk), which is based 
on libparted (the same library that underlies parted and GParted, among 
others). It's been a while since I've done anything with it, and I'm not 
even sure what Linux package(s) might hold it in common distributions; 
but it has a user interface that's similar to that of util-linux's 
fdisk, but completely different internals.

-- 
Rod Smith
rod...@ro...
http://www.rodsbooks.com