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<H1>[Mageia-discuss] partitioning bug</H1>
<B>blind Pete</B>
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TITLE="[Mageia-discuss] partitioning bug">0123peter at gmail.com
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<I>Thu Jul 12 14:03:21 CEST 2012</I>
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<PRE>andre999 wrote:
><i> blind Pete a écrit :
</I>>><i> andre999 wrote:
</I>>><i>
</I>>><i>
</I>>>><i> blind Pete a écrit :
</I>>>><i>
</I>>>>><i> David W. Hodgins wrote:
</I>>>>><i>
</I>>>>><i>
</I>>>>><i>
</I>>>>>><i> On Fri, 06 Jul 2012 04:03:34 -0400, blind Pete
</I>>>>>><i> <<A HREF="https://www.mageia.org/mailman/listinfo/mageia-discuss">0123peter at gmail.com</A>> wrote:
</I>>>>>><i>
</I>>>>>><i>
</I>>>>>><i>
</I>>>>>>><i> Morgan Leijström wrote:
</I>>>>>>><i>
</I>>>>>>><i>
</I>>>>>>>><i> It would also be interesting to know what other tools say.
</I>>>>>>>><i> gparted?
</I>>>>>>>><i>
</I>>>>>>>><i>
</I>>>>>><i>
</I>>>>>><i>
</I>>>>>>><i> Gparted looks pretty. As far as I can see, gparted agrees
</I>>>>>>><i> with what I think things should look like. Gparted and
</I>>>>>>><i> fdisk agree about the number of sectors. (More than you
</I>>>>>>><i> get by multiplying CxHxS.)
</I>>>>>>><i>
</I>>>>>>><i>
</I>>>>>><i> Interesting. I guess it would be best to use 'hdparm -i /dev/sda|grep
</I>>>>>><i> LBAsects" to find out the number of sectors.
</I>>>>>><i>
</I>>>>>><i> Regards, Dave Hodgins
</I>>>>>><i>
</I>>>>>><i>
</I>>>>><i> [<A HREF="https://www.mageia.org/mailman/listinfo/mageia-discuss">root at live</A> ~]# hdparm -i /dev/sda | grep LBA
</I>>>>><i> CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=1953523055
</I>>>>><i> [<A HREF="https://www.mageia.org/mailman/listinfo/mageia-discuss">root at live</A> ~]#
</I>>>>><i>
</I>>>>><i> Same number of sectors as gparted and fdisk report. Number of heads
</I>>>>><i> and sectors per cylinder are just, "it's a big disk". _Posssibly_
</I>>>>><i> number of cylinders gives a clue about how big. H can be 63 or 255,
</I>>>>><i> depending on mood, and CxHxS should be a little less than max LBA.
</I>>>>><i>
</I>>>>><i> The situation just got worse. The latest work arround is to lie
</I>>>>><i> about how big a sector is. That is called "advanced" formatting.
</I>>>>><i>
</I>>>>><i>
</I>><i>
</I>>>><i> BTW, with all those partitions, I would convert your disk to GPT tables
</I>>>><i> instead of MBR, using gdisk.
</I>>>><i> (gdisk is in core.)
</I>>>><i>
</I>>><i> OK I have installed gdisk and will look at it. How would you rate
</I>>><i> it for maturity? And what else can recognize a gpt disk?
</I>><i>
</I>><i> I would say very mature, even when I started using it (under mdv 2010.0
</I>><i> or 2010.1)
</I>><i> The developer says the "hybid" option which simulates MBR for Msw is
</I>><i> risky, but even that I found very stable and predictable
</I>
I let it loose on my test machine. It has Lilo on the mbr. Mageia 1
with Grub in its root partition, Mageia 2 with Grub in its root
partition, and Ubuntu 10.04.4 with Grub 2 in its root partition.
Converting to gpt confused Ubuntu's Grub 2.
Experimenting with a hybrid system, converting a primary
to a logical, adding a new primary, and renumbering confused
lots of things.
It was only the test computer.
>><i> Grub?
</I>>><i>
</I>><i> Yes, since 1.97 patched for GPT, as used in mdv and fedora (at least)
</I>><i> when I started using GPT.
</I>><i> Mageia has always used this version.
</I>>><i> Grub2?
</I>>><i>
</I>><i> Definitely
</I>
I managed to confuse it. Posibly by having it installed in the
root partition.
>><i> Lilo?
</I>>><i>
</I>><i> Not sure. I think newer versions do.
</I>
Mostly works. The mbr code just jumps to a hardcoded sector
address and loads the real code from what is normally /etc/map.
>><i> The Mageia installer?
</I>>><i>
</I>><i> I didn't have a problem. I did an upgrade install from mdv2010.2 to
</I>><i> mga1, and could read the other partitions to set up fstab.
</I>><i> Sometime before mga1 was available, I had a problem which corrupted my
</I>><i> system, and made it unbootable. It took me a while to get around that,
</I>><i> as I didn't want to loose my uncorrupted partitions. I ended up fixing
</I>><i> it with SystemRescueCD (it contains a partition recovery tool called
</I>><i> testdisk.) I was able to reinstall mdv. I may have formatted / with
</I>><i> SystemRescueCD. At that point I had a "hybrid" format simulating MBR
</I>><i> for systems not aware of GPT.
</I>
Is there any option in the installer to turn the disk into a gpt disk?
>><i> Other installers?
</I>>><i>
</I>>><i> Other operating systems?
</I>>><i>
</I>><i> According to what I have read, most other major distros handle GPT
</I>><i> nicely. The Linux kernel does.
</I>><i> Msw 32-bit does not, but can work with gdisks' "hybrid" format, which
</I>><i> puts an MBR table at the end of the first sector (a space not used by
</I>><i> GPT). It is a little tricky to set up, but initially I had it working.
</I>><i> Recently I haven't been bothered to get it working again.
</I>><i> Msw 64-bit is GPT-aware, but I have read that it works only on EFT
</I>><i> hardware, which has a special BIOS. (Incompatible with Msw 32-bit.) It
</I>><i> may be just that it is the default installation.
</I>><i> MacOS handles GPT, but I'm not sure of the restrictions if any. Is was
</I>><i> an early adopter.
</I>><i> *BSD systems should handle GPT just like Linux.
</I>>>><i> It will make your disk more stable.
</I>>>><i> It uses a 128 partition table,with a backup table at the end of the
</I>>>><i> drive. No such thing as "extended" partitions.
</I>>>><i> It takes less space than the ms-compatible MBR partition tables.
</I>>>><i> The only trick is that you need to leave space for the backup table (34
</I>>>><i> 512-byte sectors).
</I>>>><i> If you change your mind, you can convert back painlessly.
</I>>>><i> I've used GPT for over 2 years, including converting back and forth a
</I>>>><i> few times at first.
</I>>>><i>
</I>>>><i> To convert, you'll have to boot to a live disk, preferably with gdisk.
</I>>>><i> I use systemRescueCD for that. <A HREF="http://www.sysresccd.org/">http://www.sysresccd.org/</A>
</I>>>><i> The latest stable version is 379 Mib, usable from CD or USB key.
</I>>>><i> I don't know if a Mageia live cd, or Mageia DVD in rescue mode might
</I>>>><i> work.
</I>>>><i>
</I>>><i> In Mageia 1 the installer pulled it from the net rather than from
</I>>><i> the local iso, so it was not prepackaged.
</I>><i>
</I>><i> I installed mga1 from DVD. This upgrade went very smoothly.
</I>><i>
</I>><i> I did have a problem changing partition parameters with diskdrake under
</I>><i> mga1, not long after installing it, shortly after mga1 was released.
</I>><i> Luckily I was testing things, so I didn't loose anything important. But
</I>><i> everything was lost on the partition in question. I then tried
</I>><i> reformatting the partition with diskdrake, and it wouldn't work. I had
</I>><i> to use SystemRescueCD (with gparted).
</I>><i> I strongly suspect it was due to my having a "hybrid" format. I think
</I>><i> that at least at that point, diskdrake (or whatever it uses) would see
</I>><i> the MBR table, and classify the disk as MBR. While still getting the
</I>><i> partition location parameters from the GPT table. (The simulated MBR
</I>><i> table puts most partitions in a large "foreign" partition. The
</I>><i> corrupted partition was not in the MBR table. And no other partition
</I>><i> was affected.)
</I>><i>
</I>><i> Note that I have never had a problem simply accessing (read or write) a
</I>><i> GPT partition on mdv or mga.
</I>><i>
</I>><i> Also, initially I used gdisk to format usb drives (but no hybrid MBR
</I>><i> table), and have never had a problem on those disks with diskdrake or
</I>><i> any other mdv or mga tools.
</I>><i>
</I>><i> BTW, I installed gdisk from upstream on mdv, and first imported gdisk to
</I>><i> Mageia.
</I>>>><i> Just in case you might be interested
</I>>>><i>
</I>>><i> I'm interested.
</I>><i>
</I>><i> You will probably find this interesting :)
</I>><i> <A HREF="http://en.wikipedia.org/wiki/GUID_Partition_Table">http://en.wikipedia.org/wiki/GUID_Partition_Table</A>
</I>
Thanks.
--
blind Pete
Sig goes here...
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