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Old 10th August 2009
gosha gosha is offline
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Default more than four primary partitions?

Hello,
Maybe this is a general question not related only to OpenBSD (4.5 release), but since I'm running OpenBSD I'll still post here.

I finally made up a reasonable set up in my new Tinkpad, keeping Vista (sometimes you can't really do without Windows, especially when some friends cannot understand why a computer should run a different OS...), shrinking it with gparted and installing OpenBSD.

The problem:
Now I have four primary partitions in mbr, three of them are taken by Vista and Lenovo stuff, one is for OpenBSD. I left quite a lot of space free, thinking of making an ext2 partitions to share files between Vista and OpenBSD. But I see that fdisk only has four slots. In Vista, the free space is recognized, and maybe I could format it to ext2, but then will OpenBSD see it?
At the beginning, I also wanted to install Opensuse, which I tried in qemu, and quite like it, so just to give a try to linux. But I see that linux makes even more partitions inside mbr, so that then OpenBSD's fdisk does not see all the partitions.
Although I've read some wikis and tutorials on the web, I think I still miss some basics. Will something like gag solve this kind of problem? (I presently use Vistas boot manager).
But again, will OpenBSD see a partition that exceeds the fdisk's four slots?
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Old 10th August 2009
BSDfan666 BSDfan666 is offline
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With MBR partitioning, you can have 3 "primary" partitions and 1 "extended" partition.. an extended partition is essentially a link to an additional partition table that again can have an additional 3 primary, 1 extended partition. (..this can keep going for quite a bit unfortunately.).

You already have 4 primary partitions, another variation.. thus you cannot create any extended partitions..

This can be quite confusing, and perhaps a GUI partitioning tool might be able to simplify it.. but the gist of what I'm telling you is that you'll need to repartition your disk, having 3 MBR partitions for Vista and for your laptops utility partition.. and the last partition being extended, afterword you can add a partition for OpenBSD and one for the EXT2/Linux stuff.

OpenBSD 4.5 supports being installed on extended partitions now, and fdisk(8) has supported manipulation of such tables for some time as well.

Please search for the "COMMAND MODE" section in that man page for more information about switching between extended table views.

OpenBSD creates "fictitious" disklabel entries for foreign partitions it finds.. but I have not confirmed that it recurses through extended partition tables.

Can anyone comment on this? I never install more then one operating system on my computer.
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Old 10th August 2009
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Quote:
Originally Posted by BSDfan666 View Post
.. an extended partition is essentially a link to an additional partition table that again can have an additional 3 primary, 1 extended partition. (..this can keep going for quite a bit unfortunately.).
These partition tables inside the extended partition will generally define just one usable "logical partition", two empties and a pointer to the next one, so they form a linked list. (My desciption is a bit loose, but that's the gist of it.) The logical partitions can't be used as a primary partition for things that really need a primary partition ... there are just 3 (or 4) of those on the disk in the MBR partition table.

Quote:
OpenBSD 4.5 supports being installed on extended partitions now ...
Interesting, didn't know that or had forgotten!

Quote:
OpenBSD creates "fictitious" disklabel entries for foreign partitions it finds.. but I have not confirmed that it recurses through extended partition tables.

Can anyone comment on this? I never install more then one operating system on my computer.
Yes, I believe that it does. Today I'm running NetBSD and here is my disklabel:

Code:
16 partitions:
#        size    offset     fstype [fsize bsize cpg/sgs]
 a:   5278896  10763550     4.2BSD   2048 16384     0  # (Cyl.  10678*-  15915*)
 b:    263529  16042446       swap                     # (Cyl.  15915*-  16176*)
 c:   5542425  10763550     unused      0     0        # (Cyl.  10678*-  16176*)
 d:  80418240         0     unused      0     0        # (Cyl.      0 -  79779)
 g:    273042        63 Linux Ext2      0     0        # (Cyl.      0*-    270*)
 h:  10490445    273105 Linux Ext2      0     0        # (Cyl.    270*-  10678*)
 i:    626472  16306038 Linux Ext2      0     0        # (Cyl.  16176*-  16798*)
 j:   6313482  16932573 Linux Ext2      0     0        # (Cyl.  16798*-  23061*)
 k:   5943987  23246118 Linux Ext2      0     0        # (Cyl.  23061*-  28958*)
 l:  10506447  29190168 Linux Ext2      0     0        # (Cyl.  28958*-  39381*)
 m:  20370357  39696678 Linux Ext2      0     0        # (Cyl.  39381*-  59590*)
 n:  20338227  60067098 Linux Ext2      0     0        # (Cyl.  59590*-  79767*)
ISTR that OpenBSD can do about the same.

Last edited by IdOp; 10th August 2009 at 03:16 AM. Reason: spelling
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Old 10th August 2009
gosha gosha is offline
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Thank you for your answers:
Quote:
Please search for the "COMMAND MODE" section in that man page for more information about switching between extended table views.
I guess this is the part of the fdisk manpage you mean:
Quote:
select #
Select and load into memory the boot block pointed to by the ex-
tended MBR partition table entry in the current boot block.
but to tell the truth it looks quite cryptic to me

So, from what you are telling me, I should be able to dump OpenBSD somewhere, and then cancel its partition and turn it into an extended partition which I could split again into a partition for OpenBSD and one for my ext2 partition, or even from there create another extended partition where I could install Opensuse.
Did I get it right?
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A small update: here is the disklabel for the same disk as above, but as provided by OpenBSD:
Code:
16 partitions:
#                size           offset  fstype [fsize bsize  cpg]
  c:         80418240                0  unused                   
  i:           273042               63  ext2fs                   
  j:         10490445           273105  ext2fs                   
  k:          5542425         10763550 unknown                   
  l:           626472         16306038  ext2fs                   
  m:          6313482         16932573  ext2fs                   
  n:          5943987         23246118  ext2fs                   
  o:         10506447         29190168  ext2fs                   
  p:         20370357         39696678  ext2fs
(I'm pretty sure this one is the default; the NetBSD one may have been edited a bit ... not sure anymore.)
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Old 10th August 2009
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I've just tried to play with fdisk on an old usb stick, and I start to understand how it works.
For the extended partition I should choose "Extended LBA" (id 0F), right?
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Quote:
Originally Posted by gosha View Post
For the extended partition I should choose "Extended LBA" (id 0F), right?
0F is W95 Ext'd (LBA) ... I think you want type 05.

ADDED: Hmmm, it seems 0x05, 0x0F and 0x85 are all used for this.

EDIT2: Thanks BSDfan666, I added the above after seeing the original version of your post. I've always gotten away with 05, but maybe there are circumstances where the other is better, so it's good to know about.

Last edited by IdOp; 10th August 2009 at 02:42 PM.
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Old 10th August 2009
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Quote:
Originally Posted by gosha View Post
I've just tried to play with fdisk on an old usb stick, and I start to understand how it works.
For the extended partition I should choose "Extended LBA" (id 0F), right?
That appears to be the agreed upon value, you can use to "setpid" command to change the type of your existing OpenBSD partition.

EDIT: @IdOp: That may be wrong, OpenBSD calls 0x05 "Extended DOS" and 0x0F "Extended LBA", considering LBA is the modern way of addressing disks.. this may be the preferred partition type marker.

EDIT2: OpenBSD appears to treat both values identically, so it doesn't matter.. it always checks for DOSPTYP_EXTEND and DOSPTYP_EXTENDL which are defined as 0x05 and 0x0F in /usr/include/sys/disklabel.h.

EDIT3: OpenBSD does not support an extended partition type id of 0x85, (Linux extended).

Last edited by BSDfan666; 10th August 2009 at 02:44 PM.
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Old 10th August 2009
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I have never been able to get the bootloader to run from an extended partition, but I've only ever tested it under Qemu. I flag the extended partition, then flag the A6 partition in the extended MBR. I get:
Quote:
Using drive 0, partition 3
Using drive 0, partition 0
No O/S
What I did learn, though, was that the extended MBR needs both a proper signature and MBR boot code (installed with the fdisk "update" command), and, that the first track (e.g. 63 sectors) should be reserved to prevent overlay, just as with the primary MBR.
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Quote:
That appears to be the agreed upon value, you can use to "setpid" command to change the type of your existing OpenBSD partition.
It means it will not touch the existing installation, no need to dump/restore, right?
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No, you'll have to recreate the OpenBSD partition within the extended partition table.. offsets will most likely be different, so you'll need to reinstall.
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Old 10th August 2009
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I managed to install OpenBSD 4.5 in QEMU on an extended partition, unfortunately as jggimi mentioned.. the bootloader is unable to boot.

This is my mistake, I do apologize.. perhaps full support is in 4.6/-CURRENT but it is clearly not available in 4.5.
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Old 10th August 2009
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I just tested under Qemu, again. I could get the bootloader to operate, if I booted it from GAG.

Any bootloader (GAG, Grub, Lilo, perhaps even Windows' boot.ini.) should work.
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Old 10th August 2009
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Ok, thank you all, I'll give it a try today, maybe Vista's bootloader will work
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Old 11th August 2009
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I've tried and I thought my partitions were all ok, but now there seems to be something lost. The machines says there's no valid operating system. Gparted also shows an empty hard disk, but this is fdisk run from an OpenBSD I installed on a usb stick:
Code:
# fdisk -e sd0
Enter 'help' for information
fdisk: 1> p g
Disk: sd0       geometry: 32301/240/63 [233 Gigabytes]
Offset: 0       Signature: 0xAA55
            Starting         Ending         LBA Info:
 #: id      C   H   S -      C   H   S [       start:        size ]
-------------------------------------------------------------------------------
 0: 07      0  32  33 -    203  74  26 [        2048:           1G] HPFS/QNX/AUX
 1: 07    203  74  27 -   7137 239  63 [     3074048:          50G] HPFS/QNX/AUX
 2: 07  30946 178  19 -  32301  57  41 [   467914752:          10G] HPFS/QNX/AUX
 3: 0F   7138   0   1 -  30945 239  63 [   107926560:         172G] Extended LBA
fdisk: 1> select 3
Selected extended partition 3
New MBR at offset 107926560.
Enter 'help' for information
fdisk: 2> p g
Disk: sd0       geometry: 32301/240/63 [233 Gigabytes]
Offset: 107926560       Signature: 0xAA55
            Starting         Ending         LBA Info:
 #: id      C   H   S -      C   H   S [       start:        size ]
-------------------------------------------------------------------------------
 0: A6   7138   0   1 -  14073 239  63 [   107926560:          50G] OpenBSD     
 1: 83  14074   0   1 -  16154 239  63 [   212798880:          15G] Linux files*
 2: 82  16155   0   1 -  16849 239  63 [   244263600:           5G] Linux swap  
 3: 83  16850   0   1 -  30945 239  63 [   254772000:         102G] Linux files*
So what have I done? Why did Vista also disappear?
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Old 11th August 2009
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I don't know what you've done. From what you've posted:

  • There is no flagged partition in your root MBR for your BIOS to boot.
  • You appear to have a valid MBR signature in your extended MBR.
  • Your OpenBSD partition begins at the same track as your extended MBR, and if you install it there, you will destroy the extended MBR. Change the starting position of the OpenBSD partition to 7138/1/1 to move it 63 sectors ahead.
  • None of your extended partitions are flagged bootable, either. But, as discussed above, our testing (in a virtual machine) indicate that flagging both the "root" extended partition and the OpenBSD partition will fail to have OpenBSD boot directly from BIOS anyway.
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Old 11th August 2009
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Thanks jggimi,
I changed the partition starting and now it seems fine, but still cannot find OpenBSD, or, the Vista bootloader does not show the extended partition as an option. I installed EasyBCD which gives the option to install NeoGrub, which I guess should solve the problem but I can't figure out how to tell NeoGrub to find the first partition of the extended partition. All examples I've found are about primary partitions inside mbr. So do you know how the entry in the configuration should be?
"hd0,X" what should the number be?
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Old 11th August 2009
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I don't know Grub or Lilo, I only use them when I absolutely have to (such as when running Linux). I would guess that Grub would assign partition #5, but it is only a guess. My bootloader of choice for multiboot systems is GAG.
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Old 11th August 2009
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I've tried (hd0,5,a) but it gives error 22 saying I should use a Vista compatible fdisk to partition the hd
How do I install gag without a floppy and without a cdrom?


Added:
Presently partition tables look like this:
Code:
Disk: sd0	geometry: 32301/240/63 [488397168 Sectors]
Offset: 0	Signature: 0xAA55
            Starting         Ending         LBA Info:
 #: id      C   H   S -      C   H   S [       start:        size ]
-------------------------------------------------------------------------------
*0: 07      0  32  33 -    203  74  26 [        2048:     3072000 ] HPFS/QNX/AUX
 1: 07    203  74  27 -   7137 239  63 [     3074048:   104852512 ] HPFS/QNX/AUX
 2: 07  30946 178  19 -  32301  57  41 [   467914752:    20480000 ] HPFS/QNX/AUX
 3: 0F   7138   1  63 -  30945 239  63 [   107926685:   359976835 ] Extended LBA
Offset: 107926685	Signature: 0x0
            Starting         Ending         LBA Info:
 #: id      C   H   S -      C   H   S [       start:        size ]
-------------------------------------------------------------------------------
 0: A6   7138   2   1 -  14072 239  63 [   107926686:   104857074 ] OpenBSD     
 1: 00      0   0   0 -      0   0   0 [           0:           0 ] unused      
 2: 00      0   0   0 -      0   0   0 [           0:           0 ] unused      
 3: 00      0   0   0 -      0   0   0 [           0:           0 ] unused

Last edited by gosha; 11th August 2009 at 11:31 AM.
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Old 11th August 2009
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Quote:
...How do I install gag without a floppy and without a cdrom?
Download GAG.
Unzip the archive.
Open the docs/index.html file in your browser.
Click on the How to install GAG link.
Read and follow the DIRECT INSTALLATION section. You'll need a running Linux system.


Alternatively, remove your hard drive and insert it in a system with a diskette or CD/DVD drive. Or, do the installation from a virtual machine with a virtual floppy / CD drive, and that has been given physical access to the entire hard drive.
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