Re: label-id and sfdisk problem

["Bartłomiej Solarz-Niesłuchowski" <Bartlomiej.Solarz-Niesluchowski@wit.edu.pl>]

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W dniu 2017-02-21 o 17:49, Karel Zak pisze:
> On Tue, Feb 21, 2017 at 05:31:25PM +0100, Bartłomiej Solarz-Niesłuchowski wrote:
>> Dear List,
>>
>> I have problem with setting label-id of dos partition table
>> The problem occurs when i use sfdisk:
>> 1. I "save" the partition table with sfdisk -d /dev/sda > saved.table (saved
>> file has label-id of partition table)
>> 2. then i restore this via sfdisk /dev/sda < saved.table
>> BUT
>> label-id of dos partition table can be changed in this operation e.g.:
>> when i run command such:
>> sfdisk -d /dev/sda > saved.table
>> sfdisk /dev/sda < saved.table
>> sfdisk -d /dev/sda
>> sfdisk /dev/sda < saved.table
>> sfdisk -d /dev/sda
>> sfdisk /dev/sda < saved.table
>> sfdisk -d /dev/sda
>>
>> each time when i restore partition table label-id of dos type partition
>> table is changed!
>>
>> For me it is essential that label-id is set exactly as previous because
>> after that i restore windows operationg system on this partitions and
>> windows take care about label-id of boot disk partition table
>>
>> Currently i use fdisk (expert option i) for setting label-id of partition,
>> but why it is not possible thru sfdisk?
> Version? I'm not able to reproduce this problem (v2.28.2 as well as
> upstream tree with incoming v2.30).
root@sysresccd /mnt % sfdisk /dev/sdb < henwar.2017.sdb.sfdisk
Checking that no-one is using this disk right now ... OK

Disk /dev/sdb: 489.1 GiB, 525112713216 bytes, 1025610768 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

 >>> Script header accepted.
 >>> Script header accepted.
 >>> Script header accepted.
 >>> Script header accepted.
 >>> Created a new DOS disklabel with disk identifier 0x1f257e1a.
Created a new partition 1 of type 'W95 FAT32 (LBA)' and of size 500 MiB.
/dev/sdb2: Created a new partition 2 of type 'HPFS/NTFS/exFAT' and of 
size 488.6 GiB.
/dev/sdb3:
New situation:

Device     Boot   Start        End    Sectors   Size Id Type
/dev/sdb1  *       2048    1026047    1024000   500M  c W95 FAT32 (LBA)
/dev/sdb2       1026048 1025607679 1024581632 488.6G  7 HPFS/NTFS/exFAT

The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

root@sysresccd /mnt % sfdisk -d /dev/sdb
label: dos
label-id: 0x1f257e1a
device: /dev/sdb
unit: sectors

/dev/sdb1 : start=        2048, size=     1024000, type=c, bootable
/dev/sdb2 : start=     1026048, size=  1024581632, type=7

root@sysresccd /mnt % less henwar.2017.sdb.sfdisk
label: dos
label-id: 0x908b462c
device: /dev/sdb
unit: sectors

/dev/sdb1 : start=        2048, size=     1024000, type=c, bootable
/dev/sdb2 : start=     1026048, size=  1024581632, type=7

root@sysresccd /mnt % sfdisk -v
sfdisk from util-linux 2.28.2

As you see sfdisk creates different label-id than it has in file

>      
>         Karel
>
>
> # modprobe scsi_debug dev_size_mb=100;
> # echo ',,L' | sfdisk  /dev/sdc
>
>          Disk /dev/sdc: 100 MiB, 104857600 bytes, 204800 sectors
>          Units: sectors of 1 * 512 = 512 bytes
>          Sector size (logical/physical): 512 bytes / 512 bytes
>          I/O size (minimum/optimal): 512 bytes / 524288 bytes
>
>          >>> Created a new DOS disklabel with disk identifier 0x6061f502.
>          Created a new partition 1 of type 'Linux' and of size 99 MiB.
>          /dev/sdc2:
>          New situation:
>
>          Device     Boot Start    End Sectors Size Id Type
>          /dev/sdc1        2048 204799  202752  99M 83 Linux
>
> # sfdisk -d /dev/sdc > saved
> # cat saved
>
>          label: dos
>          label-id: 0x6061f502
>          device: /dev/sdc
>          unit: sectors
>
>          /dev/sdc1 : start=        2048, size=      202752, type=83
>
>
> # sfdisk  /dev/sdc < saved
>
>          Disk /dev/sdc: 100 MiB, 104857600 bytes, 204800 sectors
>          Units: sectors of 1 * 512 = 512 bytes
>          Sector size (logical/physical): 512 bytes / 512 bytes
>          I/O size (minimum/optimal): 512 bytes / 524288 bytes
>          Disklabel type: dos
>          Disk identifier: 0x6061f502
>
>          Old situation:
>
>          Device     Boot Start    End Sectors Size Id Type
>          /dev/sdc1        2048 204799  202752  99M 83 Linux
>
>          >>> Script header accepted.
>          >>> Script header accepted.
>          >>> Script header accepted.
>          >>> Script header accepted.
>          >>> Created a new DOS disklabel with disk identifier 0x6061f502.
>          Created a new partition 1 of type 'Linux' and of size 99 MiB.
>          /dev/sdc2:
>          New situation:
>
>          Device     Boot Start    End Sectors Size Id Type
>          /dev/sdc1        2048 204799  202752  99M 83 Linux
>
> # sfdisk -d /dev/sdc
>
>          label: dos
>          label-id: 0x6061f502
>          device: /dev/sdc
>          unit: sectors
>
>          /dev/sdc1 : start=        2048, size=      202752, type=83
>
>
>> Best Regards
>>
>> -- 
>> Bartłomiej Solarz-Niesłuchowski, Administrator WSISiZ
>> e-mail: Bartlomiej.Solarz-Niesluchowski@wit.edu.pl
>> tel. 223486547, fax 223486501
>> JID: solarz@jabber.wit.edu.pl
>> 01-447 Warszawa, ul. Newelska 6, pokój 404, pon.-pt. 8-16
>> Motto - Jak sobie pościelisz tak sie wyśpisz
>>
>>
>
>


-- 
Bartłomiej Solarz-Niesłuchowski, Administrator WSISiZ
e-mail: Bartlomiej.Solarz-Niesluchowski@wit.edu.pl
tel. 223486547, fax 223486501
JID: solarz@jabber.wit.edu.pl
01-447 Warszawa, ul. Newelska 6, pokój 404, pon.-pt. 8-16
Motto - Jak sobie pościelisz tak sie wyśpisz



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