[Mageia-discuss] partitioning bug

Sun Jul 8 11:02:50 CEST 2012

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
+>
+> 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
+
+> Lilo?
+>    
+Not sure.  I think newer versions do.
+
+> 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.
+
+> 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
+
+-- 
+André
+
+