[Mageia-discuss] partitioning bug

Thu Jul 12 14:03:21 CEST 2012

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