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Re: DD bs=4M option on USB mem-stick creates false format

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  Re: DD bs=4M option on USB mem-stick creates false format "Thomas Schmitt" <scdbackup@gmx.net> - 2017-03-27 00:20 +0200
    Re: DD bs=4M option on USB mem-stick creates false format kAt <giathnygeia@openmailbox.org> - 2017-03-27 13:20 +0200

#179412 — Re: DD bs=4M option on USB mem-stick creates false format

Hi,

kAt wrote:
> > /sbin/fdisk -l /dev/sdb
> Disk /dev/sdb: 7.2 GiB, 7751073792 bytes, 15138816 sectors

Is this about the correct size of the stick ?


> Units: sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes

Looks like a normal block size for USB sticks and conventional disks.


> Device     Boot   Start     End Sectors  Size Id Type
> /dev/sdb1  *         64 1374207 1374144  671M  0 Empty
> /dev/sdb2       1297212 1298619    1408  704K ef EFI (FAT-12/16/32)

This is the MBR partition table. You may use fdisk to add a partition.
(Let's hope it will not hate that sdb2 is located inside sdb1.)


> echo 2 | sudo /sbin/gdisk -l /dev/sdb
> Warning! Main partition table overlaps the first partition by 64 blocks!
> You will need to delete this partition or resize it in another utility.

gdisk definitively hates the start of the outer partition.
But starting at block 64 would mean that it would not be mountable.

> Number  Start (sector)    End (sector)  Size       Code  Name
>   2         1297212         1298619   704.0 KiB   0700  ISOHybrid1

The EFI partition is more to its taste.

As said, the GPT of an ISO with "mjg" layout is quite useless
and i'd zeroize its header block at block address 1.


Have a nice day :)

Thomas

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#179433

Thomas Schmitt:
> Hi,
> 
> kAt wrote:
>>> /sbin/fdisk -l /dev/sdb
>> Disk /dev/sdb: 7.2 GiB, 7751073792 bytes, 15138816 sectors
> 
> Is this about the correct size of the stick ?

I suppose this is normal for an 8Gb usb stick. 249Mb go to firmware that
operates the stick????  I wouldn't know.

>> Units: sectors of 1 * 512 = 512 bytes
>> Sector size (logical/physical): 512 bytes / 512 bytes
>> I/O size (minimum/optimal): 512 bytes / 512 bytes
> 
> Looks like a normal block size for USB sticks and conventional disks.

So where does the false alert come from on Gparted about the 2048b?
Is it a problem with the way I restore the iso, a problem with the iso
that Rescatux forces (I wouldn't think so) or a problem with the stick
itself?

>> Device     Boot   Start     End Sectors  Size Id Type
>> /dev/sdb1  *         64 1374207 1374144  671M  0 Empty
>> /dev/sdb2       1297212 1298619    1408  704K ef EFI (FAT-12/16/32)
> 
> This is the MBR partition table. You may use fdisk to add a partition.
> (Let's hope it will not hate that sdb2 is located inside sdb1.)

why does this happen?  Again this is not an iso I created but downloaded
from Rescatux

>> echo 2 | sudo /sbin/gdisk -l /dev/sdb
>> Warning! Main partition table overlaps the first partition by 64 blocks!
>> You will need to delete this partition or resize it in another utility.
> 
> gdisk definitively hates the start of the outer partition.
> But starting at block 64 would mean that it would not be mountable.

So fdisk uses things differently than gdisk, or is the one using the other?

>> Number  Start (sector)    End (sector)  Size       Code  Name
>>   2         1297212         1298619   704.0 KiB   0700  ISOHybrid1
> 
> The EFI partition is more to its taste.

The EFI part is sdb2, right?  Which resides inside sdb1?

> As said, the GPT of an ISO with "mjg" layout is quite useless
> and i'd zeroize its header block at block address 1.

So it is normal that if you write such an iso in a 64Gb stick 63Gb
remain useless as long as this system is on it?  Strange but still
clueless of what all this means ...

> Have a nice day :)

You too

> Thomas

I am very far from undersdanding this but it is interesting to keep at it?

kAt

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